norihiroizumi

Ph. D., University of Minnesota (USA), Sep. 1993

河川水理学

安定性

土砂輸送

河川地形

River Hydraulics Fluid Mechanics Sediment Transport Fluvial Morphology

Stability

Sediment Transport

Fluvial Geomorphology

Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention), Hydroengineering

Bachelor's degree program, School of Engineering

Master's degree program, Graduate School of Engineering

Doctoral (PhD) degree program, Graduate School of Engineering

Mar. 2021, Japanese Society for Engineering Education, JSEE AWARD
Norihiro Izumi

Sep. 2013, Applied Mechanics Committee, JSCE, Best Paper Award, AMC, JSCE
Linear stability analysis of meandering with bed aggradation or degradation
Norihiro Izumi

2012, Hydraulic Committee, JSCE, Best Paper Award of Hydraulic Engineering
「河床上昇・低下を伴う砂州の線形安定解析」
高畑知明・泉 典洋, Japan

2010, Hydraulic Committee, JSCE, Best Paper Award of Hydraulic Engineering
「平坦床－反砂堆遷移過程の分岐特性」
泉典洋・Gary Parker, Japan

2006, Japan Society of Civil Engineers, Best Paper Award, JSCE
「水路群の形成機構に関する理論的研究（総合題目）」
泉典洋, Japan

1995, 土木学会水工学委員会, 土木学会水工学論文奨励賞
「チャンネルネットワークの初期形成機構」
泉典洋, Japan

Upstream‐Migrating Bars in Partially Transporting Straight Channels: Numerical Simulation and Theoretical Interpretation
Toshiki Iwasaki; Soichi Tanabe; Norihiro Izumi
Water Resources Research, Oct. 2025
Scientific journal

CAN THERE BE SOLITARY STEPS MIGRATING UPSTREAM WITH PERMANENT FORMS IN MILD-SLOPE BEDROCK RIVERS?
Norihiro IZUMI; Remi TOCHIMOTO; Takuya INOUE
Japanese Journal of JSCE, 81, 16, n/a, n/a, Japan Society of Civil Engineers, 2025, [Peer-reviewed]
Japanese, Scientific journal

GURADUALLY VARIED FLOW ANALYSIS OF SUBMARINE TURBIDITY CURRENTS ON THE CONTINENTAL SLOPE
Yuki SAITO; Norihiro IZUMI
Japanese Journal of JSCE, 81, 16, n/a, n/a, Japan Society of Civil Engineers, 2025, [Peer-reviewed]
Scientific journal

THE INFLUENCE OF WATERFALL FACE ANGLE AND DROP HEIGHT ON WATERFALL MIGRATION RATE
Mutsuki TAKASE; Takuya INOUE; Yuki HIRAMATSU; Tamaki SUMNER; Norihiro IZUMI; Tatsuhiko UCHIDA
Japanese Journal of JSCE, 81, 16, n/a, n/a, Japan Society of Civil Engineers, 2025, [Peer-reviewed]
Japanese, Scientific journal

Controls on Erosion and Cyclic Step‐Formation Upstream of Waterfalls
T. Inoue; Y. Hiramatsu; J. S. Scheingross; S. Yamaguchi; K. Takahashi
Geophysical Research Letters, 51, 22, American Geophysical Union (AGU), 22 Nov. 2024, [Peer-reviewed]
English, Scientific journal, Abstract

Waterfall retreat transmits base‐level perturbations upstream, thereby providing markers of changing climate and tectonics. In homogeneous rock, waterfalls often retreat either by direct waterfall‐face erosion or incision from repeating (‘cyclic’) steps formed above waterfalls. We lack knowledge on the conditions driving these different erosion styles, limiting our ability to predict waterfall retreat. We address this knowledge gap through flume experiments assessing how changing flow hydraulics modulates bedrock erosion. We show that, under large discharges, changes in flow hydraulics cause spatial variability in particle impact velocity, leading to cyclic step formation. As discharge decreases, both the magnitude and spatial variability of particle impact velocity decreases, causing more uniform erosion, limiting cyclic step development and potentially allowing direct erosion of the waterfall face to become the dominant retreat mechanism. These results suggest climate change and water‐resource management can alter the rate and style of waterfall retreat.

UPSTREAM MIGRATION PROCESS OF WATERFALL ON MILD SLOPE CHANNEL
Yuki HIRAMATSU; Takuya INOUE; Kazutaka TAKAHASHI; Naohiro YONEDA; Tatsuhiko UCHIDA; Norihiro IZUMI
Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, 2024, [Peer-reviewed]
Japanese, Scientific journal

EFFECTS OF CHANGE IN RIVER WIDTH ON KNICKPOINT RETREAT IN BEDROCK RIVERS
Tamaki SUMNER; Takuya INOUE; Norihiro IZUMI; Yasuyuki SHIMIZU
Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, 2024, [Peer-reviewed]
Japanese, Scientific journal

EFFECT OF THE AMOUNT OF SEDIMENT SUPPLY ON THE UPSTREAM PROGRESS OF WATERFALLS
Keiji YOKOTA; Norihiro IZUMI; Takuya INOUE; Yuki HIRAMATSU
Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, 2024, [Peer-reviewed]
Japanese, Scientific journal

Cyclic Steps Created by Flowing Water on Ice Surface
Zhuyuan Wu; Norihiro Izumi
Geosciences, 28 Apr. 2023, [Peer-reviewed]
Scientific journal

Upper and lower plane bed definitions revised
Koji Ohata; Hajime Naruse; Norihiro Izumi
Progress in Earth and Planetary Science, 9, 1, Dec. 2022, [Peer-reviewed]
English, Scientific journal

Centrifuge modeling of scale effect on hydraulic gradient of backward erosion piping in uniform aquifer under river levees
Mitsu Okamura; Yusuke Tsuyuguchi; Norihiro Izumi; Kenichi Maeda
Soils and Foundations, 62, 5, 101214, 101214, Elsevier BV, Oct. 2022, [Peer-reviewed]
English, Scientific journal

Transportational Cyclic Steps Created by Submarine Long-Runout Turbidity Currents
Zhuyuan Wu; Norihiro Izumi
Geosciences, 12, 7, 263, 263, 29 Jun. 2022, [Peer-reviewed]
English, Scientific journal

Linear stability analysis of plane beds under flows with suspended load
Koji Ohata; Hajime Naruse; Norihiro Izumi
Earth-Surface Processes, Copernicus GmbH, 27 Jun. 2022, [Peer-reviewed]
English, Scientific journal, Abstract. Plane beds develop under flows in fluvial and marine environments; they are recorded as parallel lamination in sandstone beds, such as those found in turbidites. However, whereas turbidites typically exhibit parallel lamination, they rarely feature dune-scale cross lamination. Although the reason for the scarcity of dune-scale cross-lamination in turbidites is still debated, the formation of dunes may be dampened by suspended load. Here, we perform, for the first time, linear stability analysis to show that flows with suspended load facilitate the formation of plane beds. For a fine-grained bed, suspended load can promote the formation of plane beds and dampen the formation of dunes. These results of theoretical analysis were verified with observational data of plane beds under open-channel flows. Our theoretical analysis found that suspended load promotes the formation of plane beds, which suggests that the development of dunes under turbidity currents is suppressed by the presence of suspended load.

EXPERIMENTS ON THE BANK EROSION DUE TO THE MEANDER ORIGINATED BY ALTERNATE BARS DURING DECREASING DISCHARGE
Satomi YAMAGUCHI; Norihiro IZUMI
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 78, 2, I_889, I_894, Japan Society of Civil Engineers, Mar. 2022, [Peer-reviewed]
Japanese, Scientific journal

Spatiotemporal Evolution of Bed Configurations in Mixed Bedrock-Alluvial in Uniformly Curved Channels
Mamy Rija Andriamboavonjy; Tomoya Terakado; Norihiro Izumi
Water, 14, 3, 397, 397, 28 Jan. 2022, [Peer-reviewed]
English, Scientific journal

WEAKLY UNSTEADY STABILITY ANALYSIS OF FLUVIAL BARS UNDER SLOWLY VARYING FLOW CONDITIONS
Norihiro IZUMI; Satomi KAWAMURA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 78, 2, I_949, I_954, Japan Society of Civil Engineers, 2022, [Peer-reviewed]
Japanese, Scientific journal

RIVER FLOW INVERSE ANALYSIS AND DATA ASSIMILATION
Ryota NISHIGUCHI; Shunsuke TAGATA; Kentaro KAGEYAMA; Norihiro IZUMI; Masato SEKINE
Journal of JSCE, 10, 1, 430, 442, Japan Society of Civil Engineers, 2022, [Peer-reviewed]
English, Scientific journal

THREE-DIMENSIONALITY OF TOPOGRAPHIC CHANGE NEAR THE EMBANKMENT DURING HIGH WAVES.
TAGATA Shunsuke; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 78, 2, I_109, I_114, Japan Society of Civil Engineers, 2022, [Peer-reviewed]
Japanese, Scientific journal, On the Suruga coast, Typhoon Hagibis caused three-dimensional topographic changes near the embankment. The slope of the beach profile in the offshore direction became steeper and became more gradual as wave height increased. The slope of the beach profile after high waves was equal to the previous empirical equation. The slope of the coastal profile in the longshore direction was uniformly changed by high waves, but became steeper only on the north side in the later stage of the typhoon, resulting in a three-dimensional topographic change. The three-dimensional topographic changes was caused by the outflow of coastal vegetation, which caused a difference in elevation, and the development of a dominant longshore current.

PROPOSAL OF EVALUATION, VISUALIZATION, AND ANALYSIS SYSTEM WHICH REALIZES VERSATILE DATA HANDLING FOR HIGHLY-SOPHISTICATED RIVER MANAGEMENT TOWARD REDUCTION OF EFFORT
FUJIWARA Keiya; SATO Makoto; KAMEDA Toshihiro; IZUMI Norihiro; HORI Muneo
Advances in River Engineering, 28, 247, 252, Japan Society of Civil Engineers, 2022, [Peer-reviewed]
Japanese, Scientific journal, 河川分野において，近年 BIM/CIMデータや ALB測量成果などの 3Dデータが蓄積されている．活用法の検討にあたっては，特に三次元管内図の全河川運用開始（2025 年度目標）に向けて各河川で動いているところである．本研究では，データの更新や河川管理者のニーズに応じたシステムの効果的・長期的な運用を目的に，各河川事務所で個別に開発されている三次元管内図や，その他既存の河川管理システムと連携可能な，オープンソースによる共通基盤の整備を提案した．また，共通基盤開発の端緒として，釜無川をフィールドに，オープンソースの三次元 WebGISによる可視化と河川シミュレーションの省力化により治水安全性や施設安全性の定量的評価が可能なアプリケーションを構築した．将来像として，システムの拡張性を担保しながら， Webブラウザを通してあらゆる関係者が協働して 3次元データをベースに河川の定量的な評価を実施し，合意形成の迅速化を目指す，河川管理の高度化の実現を提案した．

Equilibrium cross-sectional shapes of river channels self-formed by the deposition of fine sand on gravel beds
Norihiro IZUMI; Haruo IWASE; Keiji NOMURA
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 77, 2, I_739, I_744, Japan Society of Civil Engineers, Sep. 2021, [Peer-reviewed], [Lead author]
Japanese, Scientific journal, There are many examples that, although a river has been widened to improve its discharge capacity, the channel cross-sectional area has reduced due to the subsequent deposition of fine sand. The reduction of cross-sectional areas is a severe problem for maintaining an essential function of rivers to discharge floodwaters safely. In this study, we applied the theory of self-formed channels of gravel-bed sandbank rivers by Izumi and Parker to theoretically study the reduction of channel cross-sectional area due to fine sand deposition as described above and the formation of equilibrium cross-sectional shapes by fine sand deposition on gravel beds.

Climate Change Impact on the Hydrologic Regimes and Sediment Yield of Pulangi River Basin (PRB) for Watershed Sustainability
Warda Panondi; Norihiro Izumi
SUSTAINABILITY, 13, 16, Aug. 2021, [Peer-reviewed]
English, Scientific journal

The self-formation process of gravel-bed rivers with riverbanks composed of fine sediment
Izumi, N; Iwase, H; Sakai, N; Nomura, K
Advances in River Engineering, 27, 451, 456, Japan Society of Civil Engineers, Jun. 2021, [Peer-reviewed]
Japanese, Scientific journal

十勝川で始まる新たな治水の試み—New Flood Risk Management Initiating in the Tokachi River—大河川の歴史(第14回)十勝川・仁淀川 ; 十勝川
泉 典洋
河川, 77, 1, 12, 15, 日本河川協会, Jan. 2021, [Invited]
Japanese

EFFECTS OF THE VARIATION OF DISCHARGE ON THE GROWTH OF FLUVIAL BARS
IZUMI Norihiro; TAKATSU Michiaki; KAWAMURA Satomi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 77, 2, I_451, I_456, Japan Society of Civil Engineers, 2021, [Peer-reviewed]
Japanese, Scientific journal, It has been observed that the bank erosion takes place not at the peak of discharge but during the decrease in discharge. We perform linear stability analysis for the formation of alternate bars including the effect of the variation of discharge. We assume that the variation of discharge is sufficiently slower than the variation of bed elevation, and introduce two different time scales: the time for the variation of bed elevation �� and that for the variation of discharge ��. With the use of the multiple scale expansion method, we obtain the growth rate of perturbation as a function of ��. It is found that the bed is more unstable when the discharge is smaller than the peak in the range of large wavenumbers in particular.

PROGRESS OF EROSION AND WAVES NEAR THE COASTAL EMBANKMENT DURING TYPHOON HAGIBIS ON THE SURUGA COAST
TAGATA Shunsuke; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 77, 2, I_337, I_342, Japan Society of Civil Engineers, 2021, [Peer-reviewed]
Japanese, Scientific journal, Waves from Typhoon Hagibis were observed by observation equipment installed near the embankment of the Suruga Coast. Five ultrasonic wave gages, three capacitance wave gages, and a far-infrared camera were used for continuous observation at 0.3-second intervals.

 As a result of Typhoon Hagibis, sixty waves reached the vicinity of the embankment during the observation period, and these waves caused vertical beach erosion of about 20-50 cm. The erosion process was classified into four stages according to the erosion speed. From the images taken by the far-infrared camera, the average flow velocity during uprush and down-rush of the measured section was determined and compared with the amount of drift sand, which was found to be correlated with the cube of the flow velocity during the rapid erosion stage.

Engineering Education in Japan in the Post-Pandemic Era
IZUMI Norihiro
Journal of JSEE, 69, 5, 5_2, 5_2, Japanese Society for Engineering Education, 2021, [Invited]
Japanese, Scientific journal

Hysteresis Observed in the Stage-Discharge Relationship During Floods
泉典洋
ながれ, 40, 1, 2021, [Invited]
Japanese

Special issue on the heavy rain event of July 2018 in western Japan
Tatsuhiko Uchida; Yoshihisa Akamatsu; Yoshiharu Suzuki; Shuji Moriguchi; Yasushi Oikawa; Hiromi Shirahata; Norihiro Izumi
Journal of Japan Society of Civil Engineers, 9, 1, 1, 7, 2021, [Invited]
English, Scientific journal

Seepage flow analysis of double layer foundation around a river levee with the use of a simple mathematical model
Izumi, N.; Maeda, K.; Okamura, M.
Journal of Japan Society of Civil Engineers, B1 (Hydraulic Engineering), 76, 2, I_325, I_330, Nov. 2020, [Peer-reviewed]
Japanese, Scientific journal

INVERSE ANALYSIS AND DATA ASSIMILATION OF RIVER FLOW
西口亮太; 田方俊輔; 陰山建太郎; 泉典洋; 関根正人
土木学会論文集 B1(水工学), 76, 1, Nov. 2020, [Peer-reviewed]
Japanese

内外の基礎地盤特性が河川堤防のパイピング破壊に及ぼす影響と堤防調査方法の提案
前田 健一; 泉 典洋
河川技術論文集, 26, 467, 472, 2020, [Peer-reviewed]
Scientific journal

INFLUENCE OF FOUNDATION GROUND INSIDE AND OUTSIDE RIVER LEVEE ON PIPING FAILURE AND PROPOSAL OF LEVEE INVESTIGATION METHOD
高辻理人; 前田健一; 牧洋平; 伊神友裕; 泉典洋
河川技術論文集, 26, 499, 504, 2020, [Peer-reviewed]
Japanese, Scientific journal

A CONSIDERATION ON THE EFFECTS AND ISSUES OF PREVENTIVE MEASURES FOR THE LEVEE COLLAPSE CAUSED BY BANK EROSION IN THE OTOFUKE RIVER-VERIFICATION OF RISK EVALUATION PERFORMED FOR THE SERIOUS BANK EROSION DUE TO CHANGES IN WATERCOURSES-
柏谷和久; 桑村貴志; 泉典洋; 渡邊康玄; 山口里実; 横山洋
河川技術論文集, 26, 503, 508, 2020, [Peer-reviewed]
Japanese, Scientific journal

PROPOSAL FOR INSPECTION FLOW OF PIPING RISK IN RIVER LEVEES BASED ON THE RESULTS OF ACTURAL LEVEES SURVEY
西村柾哉; 前田健一; 高辻理人; 牧洋平; 泉典洋
河川技術論文集, 25, 499, 504, 12 Jun. 2019, [Peer-reviewed]
Japanese

Special issue on the heavy rain event of July 2018
Izumi, N; Uchida, T; Akamatsu, Y; Suzuki, Y; Moriguchi, S; Oikawa, Y; Shirahata, H
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 75, 1, 138, 142, 2019, [Invited]
Japanese, Scientific journal

MECHANISMS TO MAINTAIN AND ANNIHILAITE WATERFALLS FORMED ON BEDROCK
Izumi, N.; Inoue, T.; Takeda, K.
土木学会論文集 B1(水工学), 75, 2, 2019, [Peer-reviewed]

Disastrous sediment discharge due to typhoon-induced heavy rainfall over fossil periglacial catchments in western Tokachi, Hokkaido, northern Japan
Takahisa Furuichi; Nobutomo Osanai; Shin-ichiro Hayashi; Norihiro Izumi; Tomoko Kyuka; Yasuhiro Shiono; Tomoyoshi Miyazaki; Tomoya Hayakawa; Norihiro Nagano; Naoki Matsuoka
Landslides, 15, 8, 1645, 1655, Aug. 2018, [Peer-reviewed]
English, Scientific journal

Real-time water level prediction using adjoint sensitivity analysis (2)
Nishiguchi, R; Dan, T; Izumi, N
河川技術論文集, 24, 227, 232, Jun. 2018, [Peer-reviewed]
Japanese, Scientific journal

河川堤防のパイピング危険度の力学的簡易点検フローと漏水対策型水防工法の効果発揮条件
西村柾哉; 前田健一; 櫛山総平; 高辻理人; 泉典洋
河川技術論文集, 24, 01 Jun. 2018, [Peer-reviewed]
Japanese, Scientific journal

Linear stability analysis of open-channel flow overlying a porous medium
A. C. Lima; N. Izumi
Journal of Hydraulic Research, 56, 2, 211, 220, 04 Mar. 2018, [Peer-reviewed]
English, Scientific journal

THE EFFECT OF BRANCHED CHANNEL MAINTENANCE ON RIVER CHANNEL EVOLUTION DURING FLOODS
住友慶三; 渡邊康玄; 泉典洋; 山口里実; 米元光明
土木学会論文集 B1(水工学), 74, 5, 2018, [Peer-reviewed]

EQUILIBRIUM THICKNESS OF THE HIGH-CONCENTRATION LAYER FORMED AT LOWER TURBIDITY CURRENTS
泉典洋
土木学会論文集 B1(水工学), 74, 5, 2018, [Peer-reviewed]

Study on the effects of artificial flood for river channel disturbance in the maintenance of old watercourses
Keizo Sumitomo; Yasuharu Watanabe; Norihiro Izumi; Satomi Yamaguchi; Hideaki Yokohama
Journal of Japan Society of Civil Engineers, 6, 1, 69, 77, 2018, [Peer-reviewed]
Scientific journal

ANALYSIS OF BEDLOAD COLLISION VELOCITY NEAR A KNICKPOINT USING PTV METHOD
山口進; 井上卓也; 赤堀良介; 佐藤大介; 清水康行; 泉典洋
土木学会論文集 B1(水工学), 74, 5, I_1153, I_1158, 2018, [Peer-reviewed]
Japanese, Scientific journal

STRUCTURE OF OPEN-CHANNEL FLOW WITH SUBMERGED VEGETATION
Kazuhisa Tsunekawa; Adriano C. de Lima; Norihiro Izumi
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 4, Ⅰ_571, 576, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

NONLINEAR STABILITY ANALYSIS OF FREE SURFACE FLOW
Aika Hisahara; Adriano Coutinho de Lima; Norihiro Izumi
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 4, Ⅰ_607, I_612, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

EXPERIMENTAL STUDY ON MIXED BEDROCK-ALLUVIAL BED EROSION IN ANNULAR FLUME FLOW
S. Taguchi; S. Kobayashi; A. C. de Lima; N. Izumi
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 4, Ⅰ_1039, I_1044, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

BED INSTABILITY GENERATED BY TURBIDITY CURRENTS
S. Pen; N. Izumi; S. Hagisawa
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 4, Ⅰ_1105, I_1110, 土木学会, 2018, [Peer-reviewed]
English, Scientific journal

INFLUENCE OF SEDIMENT DYNAMICS IN RIVER CHANNEL ON THE CHANNEL CHANGE
S. Yamaguchi; T. Kyuka; Y. Shimizu; N. Izumi; Y. Watanabe; R. Iwasaki
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 4, Ⅰ_1153, I_1158, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

EQUILIBRIUM THICKNESS OF THE HIGH-CONCENTRATION LAYER FORMED AT LOWER TURBIDITY CURRENTS
Norihiro Izumi
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 5, I_811, I_816, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

THE EFFECT OF BRANCHED CHANNEL MAINTENANCE ON RIVER CHANNEL EVOLUTION DURING FLOODS
Keizo Sumitomo; Yasuharu Watanabe; Norihiro Izumi; Satomi Yamaguchi; Mitsuaki Yonemoto
Journal of Japan Society of Civil Engineers Ser. B1 (Hydraulic Engineering), 74, 5, I_1003, I_1008, 土木学会, 2018, [Peer-reviewed]
Japanese, Scientific journal

Initiation of Channel Head Bifurcation by Overland Flow
Adichai Pornprommin; Norihiro Izumi; Gary Parker
Journal of Geophysical Research: Earth Surface, 122, 12, 2348, 2369, 01 Dec. 2017, [Peer-reviewed]
English, Scientific journal

異なる基礎地盤特性の堤防の噴砂動態・パイピング挙動と漏水対策型水防工法の効果
西村柾哉; 前田健一; 櫛山総平; 泉典洋; 齊藤啓
河川技術論文集, 23, 381, 386, 土木学会, 05 Jun. 2017, [Peer-reviewed]
Japanese, Scientific journal

A study of the severe flood disaster in the Pekerebetsu River caused by the record-breaking rainfall in Hokkaido, 2016
Kyuka, T; Shimizu, Y; Miyamoto, T; Kenmotsu, H; Sakatani, K; Izumi, N; Yamaguchi, S; Iwasaki, T; Ishida, Y
河川技術論文集, 23, 55, 60, Jun. 2017, [Peer-reviewed]
Japanese, Scientific journal

Verification of damages due to levee breaches and back-flow from landside at the confluence of the Satsunai and Tottabetsu Rivers
Ishida, Y; Yamaguchi, S; Kyuka, T; Iwasaki, T; Shimizu, Y; Kawamura, I; Izumi, N
河川技術論文集, 23, 1, 6, Jun. 2017, [Peer-reviewed]
Japanese, Scientific journal

EXPERIMENTAL STUDY ON BEDROCK INCISION AND BED CONFIGURATION IN ANNULAR FLUME FLOW
TAGUCHI Shinya; OZAWA Haruki; LIMA Adriano C; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_847, I_852, 公益社団法人 土木学会, 2017, [Peer-reviewed]
Japanese, Scientific journal, &nbsp;Degradation of exposed bedrock takes place in many rivers worldwide, posing problems of current high interest for river management. Erosion in bedrock rivers is often caused by abrasion from moving sand particles, which is directly linked to the distribution of the alternating zones of exposed bed rock and bed covered with sediment. Erosion by abrasion is active only in a portion moderately covered with sediment. Where there is no sediment and bedrock is completely exposed, no abrasion takes place. And where the bed is fully covered with sediment, no abrasion takes place as well because of the cover effect of the sand.<br>&nbsp;In the present work, we study experimentally the occurrence of bed degradation in an annular covered flume flow with a simulated bedrock. In curving bedrock channels, due to secondary flow, sand accumulates in the inner bank while the bed is exposed in the outer bank. In the experiment, patterns of topo- graphic changes along the bed could be observed. We correlate the experimental results with expected flow patterns and erosion processes.

STUDY ON BATHYMETRY CHANGES IN THE LOWER REGIME BY TSUNAMI
ODA Keisuke; MAEDA Yuuji; NISHIURA Daisuke; NOMURA Shun; IZUMI Norihiro; NISHIHATA Takeshi; SAKAGUCHI Hide
Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 73, 2, I_660, I_665, 公益社団法人 土木学会, 2017, [Peer-reviewed]
Japanese, Scientific journal, &nbsp;A large amount of sediment is transported by tsunami. While there are many studies on the amount of sediment transport or bathymetry changes by tsunami under the condition of active sediment transport, there are only few studies in the lower regime. In addition, not many studies have focused on the unsteady processes of bathymetry changes due to the propagation of tsunami. This research aims to evaluate the tsunami force, and to study the relationship between the force and bathymetry changes in the lower regime by movable-bed experiments. It was observed that ripples are formed when waves subsequent to the tsunami front reach the bed. The bathymetry changes can be classified by the method used in rivers. The relationship between the spatial distribution of grain size and shear stress observed in the experiments is consistent to existing studies.

Incisional cyclic steps of permanent form in mixed bedrock-alluvial rivers
Norihiro Izumi; Miwa Yokokawa; Gary Parker
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 122, 1, 130, 152, Jan. 2017, [Peer-reviewed]
English, Scientific journal

Spatial and Temporal Growth of Perturbations in Open-Channel Viscous Transverse Shear Flow
Adriano C. de Lima; Norihiro Izumi
JOURNAL OF HYDRAULIC ENGINEERING, 142, 12, Dec. 2016, [Peer-reviewed]
English, Scientific journal

Numerical Simulation of Effects of Sediment Supply on Bedrock Channel Morphology
T. Inoue; T. Iwasaki; G. Parker; Y. Shimizu; N. Izumi; C. P. Stark; J. Funaki
JOURNAL OF HYDRAULIC ENGINEERING, 142, 7, Jul. 2016, [Peer-reviewed]
English, Scientific journal

基盤漏水に伴う噴砂及びパイピング進行条件の検討
齊藤啓; 前田健一; 泉典洋
河川技術論文集, 22, 251, 354, 土木学会, 02 Jun. 2016, [Peer-reviewed]
Japanese, Scientific journal

Cyclic steps on ice
M. Yokokawa; N. Izumi; K. Naito; G. Parker; T. Yamada; R. Greve
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 121, 5, 1023, 1048, May 2016, [Peer-reviewed]
English, Scientific journal

Identification of factors that may affect the discharge flow at a bottleneck
Daisuke Yamaguchi; Takashi Okano; Hajime Sudo; Masahiko Kobayashi; Takayuki Ogihara; Norihiro Izumi; Atsushi Tanaka; Toshio Yoshii
INTERNATIONAL SYMPOSIUM ON ENHANCING HIGHWAY PERFORMANCE (ISEHP), (7TH INTERNATIONAL SYMPOSIUM ON HIGHWAY CAPACITY AND QUALITY OF SERVICE, 3RD INTERNATIONAL SYMPOSIUM ON FREEWAY AND TOLLWAY OPERATIONS), 15, 356, 365, 2016
English, International conference proceedings

A CONSIDARATION ON THE GENERATING MECHANICS OF EXCESS PORE WATER PRESSURE IN THE SANDY GROUND INDUCED BY FREE SURFACE FLOW
MATSUDA Tatsuya; MAEDA Kenichi; IZUMI Norihiro; ITO Yoshimi; YAMAGUCHI Atsushi; TSURUGASAKI Kazuhiro; MIYAMOTO Junji
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 72, 2, I_565, I_570, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese, &nbsp;The object of this study is clarified to the mechanism of scouring in sandy ground due to the tractive force and seepage force. Especially, in this paper, are discussed to generating of excess pore water pressure induced by free surface flow by the movable bed experiment and exact theory. As a result, seepage flow in the ground surface was generated by free surface flow and the excess pore water pressure was generating induced by differential of velocity in seepage in extreme surface of ground. Therefore, we confirmed that generating the excess pore water pressure in extreme surface of ground was influenced by seepage flow by compared by an experimental result and exact solution.

STUDY ON THE MAINTENANCE OF FORMER WATERCOURSES BY THE ARTIFICIAL FLOOD FOR RIVER CHANNEL DISTURBANCE
SUMITOMO Keizo; WATANABE Yasuharu; IZUMI Norihiro; YAMAGUCHI Satomi; YOKOHAMA Hideaki
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 72, 4, I_751, I_756, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese, &nbsp;The effect of the artificial flood to river channel disturbance is clarified quantitatively using the results of field observations and numerical simulations (iRIC Nays2D 4.2). The 1st viewpoint is maintenance of distributary leading to former watercourses which induces river channel disturbance at the time of a large flood. The 2nd viewpoint is a scale of river channel disturbance at the time of a large flood. The difference between the existence and non-existence of the artificial flood has been discussed. It was evaluated quantitatively that artificial flood is effective in maintenance of distributaries. Moreover, it was found quantitatively that the effect of mainstream alternation at bifurcations during a large flood which is expected by the maintenance of distributaries.

BOUNDARY WAVES FORMED ON THE ICE FLOOR DUE TO KATABATIC WIND
SUMIDA Takashi; IZUMI Norihiro; YOKOKAWA Miwa; YAMADA Tomohito
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 72, 4, I_739, I_744, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese, The spiral troughs on Mars' polar ice caps are considered as cyclic steps formed on ice due to katabatic wind. Katabatic wind is a type of density current which flows downward pulled by gravity because of the denser air cooled by the ice floor. Due to the spatial non-uniformity of solidification of water vapor included in the air onto the ice floor, and sublimation of ice into the air, the boundary waves are formed on the ice floor. We performed laboratory experiments simulating the condition that katabatic wind blows on ice. Boundary waves were formed on the ice in the case that there was a large difference in temperature between the room air and the bottom of the ice.

Morphodynamics on the Ice Floor
Izumi Norihiro
JOURNAL OF GEOGRAPHY-CHIGAKU ZASSHI, 125, 1, 105, 119, 2016, [Peer-reviewed]
Japanese

Stability Evaluation against Seepage and Piping of River Levee with Permeable Base Layer under Scenarios of Rapid Seepage with Heavy Rainfall and High Water Level with Long Duration
Saitoh Hiroshi; Maeda Kenichi; Izumi Norihiro; Kobayashi Tsuyoshi
Soil and Foundation, 63, 9, 30, 33, 地盤工学会, Sep. 2015, [Peer-reviewed]
Japanese

基盤の地盤特性が異なる河川堤防の高水位の継続作用による漏水とパイピングの進行特性
齊藤啓; 前田健一; 泉典洋; 李兆卿
河川技術論文集, 22, 349, 354, 01 Jun. 2015, [Peer-reviewed]
Japanese, Scientific journal

BAR INSTABILITY WITH BANK EROSION
UDDIN Md Jahir; IZUMI Norihiro; HASEGAWA Kazuyoshi; WATANABE Yasuharu
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_121, I_126, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, Linear stability analysis of sand fluvial bars with bank erosion is performed with the use of the shallow-water equations. We assume that the average total channel width is constant, and the bank erosion takes place due to increases in the bed shear stress in the vicinity of banks. We obtain analytical solution by the use of asymptotic expansions around the state of no bank erosion (the bank erosion coefficient γequals 0) in order to clarify the effect of bank erosion on the instability of sand bars with different lateral wavenumbers. We obtain instability diagram for γ evaluated from field and experimental data, and found that bank erosion stabilizes the bed in the ranges of small wavenumbers, and of large wavenumbers and aspect ratios.

BOUNDARY WAVES FORMED ON ICE BY TURBULENT FLOW
NAITO Kensuke; IZUMI Norihiro; YOKOKAWA Miwa; SUMITA Takashi
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_1027, I_1032, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, A linear stability analysis of interfacial instability induced by turbulent flow on the ice surface is performed by the use of the Reynolds-averaged Navier-Stokes equations incorporated with the mixing length turbulent model, the heat transfer equations in ice and flow,and the Stefan condition to describe the time evolution of the ice surface.It is found from the analysis that, if the outside air temperature is higher than the melting point and the ice bottom temperature is lower than the melting point, antidune-like boundary waves are formed on the ice surface while, if the outside air temperature is lower than the melting point,dune-like boundary waves are formed on theice surface.

AN EXPERIMENTAL STUDY FOR MORPHOLOGY OF CYCLIC STEPS ON MODEL BEDROCKS
YOKOKAWA Miwa; KYOGOKU Akitoshi; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_997, I_1002, 公益社団法人 土木学会, 2015, [Peer-reviewed]
Japanese, In rivers in mountain areas, a series of steps are often observed on bedrock. They are thought to be cyclic steps formed due to erosion of bedrock, which should be driven by abrasion due to bedload sediment transport. We demonstrated a series of flume experiments of the formation of cyclic steps on bedrock by abrasion due to bedload transportation using weak mortar as the model bedrock. The shapes of cyclic steps are dependent on the sand feed rate under the water discharge of this experiment, i.e., a short upstream-facing slope and a long downstream facing slope for the lower sand feed rates, whereas long upstream-facing slope and a short and steep downstream facing slope for the higher sand feed rates. This result differ from our previous study, whose water discharge was lower and the shape of the steps was independent from the sand feed rate. In the case of higher discharge, sediment cover affects the location of vortices caused by the hydraulic jumps to make the short and steeper downstream facing slope.

BOUNDARY WAVES FORMED ON ICE BY TURBULENT FLOW
NAITO Kensuke; IZUMI Norihiro; YOKOKAWA Miwa; SUMITA Takashi
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_1027, I_1032, 公益社団法人 土木学会, 2015, [Peer-reviewed]
Japanese, A linear stability analysis of interfacial instability induced by turbulent flow on the ice surface is performed by the use of the Reynolds-averaged Navier-Stokes equations incorporated with the mixing length turbulent model, the heat transfer equations in ice and flow,and the Stefan condition to describe the time evolution of the ice surface.It is found from the analysis that, if the outside air temperature is higher than the melting point and the ice bottom temperature is lower than the melting point, antidune-like boundary waves are formed on the ice surface while, if the outside air temperature is lower than the melting point,dune-like boundary waves are formed on theice surface.

QUASI-MEANDERING INDUCED BY FLUVIAL SAND BARS
UDDIN Md Jahir; IZUMI Norihiro; HASEGAWA Kazuyoshi; PORNPROMMIN Adichai
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_1021, I_1026, 公益社団法人 土木学会, 2015, [Peer-reviewed]
Japanese, Linear stability analysis of the formation of fluvial sand bars with bank erosion is performed with the use of St.Venant shallow water equations and continuity equation, and a process-based bank erosion model. The process-based bank erosion model is derived from the integration of sediment continuity equation in the bank region. The time variation of bank locaion is proportional to the lateral sediment transport rate at the junction between bed and bank regions, which is evaluated by the lateral sediment transport rate in the bank region. and the time variation of the bed elevation at the junction. It is found from the analysis that quasi-meandering with the wavelength slightly shorter than bars takes place with the formation of bars in the range of moderately large aspect ratios.

ROTATING FLUID EXPERIMENT WITH BOTTOM SUBJECTED TO HEATED AND COOLED
ICHINOSE Rinko; KITANO Yoshikazu; YAMADA Tomohito. J; WATANABE Yasunori; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_289, I_294, 公益社団法人 土木学会, 2015, [Peer-reviewed]
Japanese, Scientific journal, &nbsp;The weather condition in the middle latitudes is controlled by westerly wind and high and low pressures, and these phenomena are interpreted as the baroclinic instability waves. A rotating fluid experiment by Fultz and Hide are known as the typical laboratory experiments of baroclinic instability waves. In this study, we introduced a new equipment having the unique feature characterized by the heated and cooled bottom. By this condition, 4-6 zonal wave numbers were observed and flow field were dynamically changed with time. At the same time, it was observed that the vorticity on center changed with baroclinic waves with time.

Macro-roughness model of bedrock-alluvial river morphodynamics
L. Zhang; G. Parker; C. P. Stark; T. Inoue; E. Viparelli; X. Fu; N. Izumi
EARTH SURFACE DYNAMICS, 3, 1, 113, 138, 2015, [Peer-reviewed]
English, Scientific journal

Interaction among alluvial cover, bed roughness, and incision rate in purely bedrock and alluvial-bedrock channel
Takuya Inoue; Norihiro Izumi; Yasuyuki Shimizu; Gary Parker
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 119, 10, 2123, 2146, Oct. 2014, [Peer-reviewed]
English, Scientific journal

On the nonlinear development of shear layers in partially vegetated channels
A. C. Lima; N. Izumi
PHYSICS OF FLUIDS, 26, 8, Aug. 2014, [Peer-reviewed]
English, Scientific journal

Linear Stability Analysis of Open-Channel Shear Flow Generated by Vegetation
Adriano C. de Lima; Norihiro Izumi
JOURNAL OF HYDRAULIC ENGINEERING, 140, 3, 231, 240, Mar. 2014, [Peer-reviewed]
English, Scientific journal

OBSERVATIONS ON CHARACTERISTICS OF WASHED AWAY OF YOUNG SALICACEAE BY FLASH FLOW FROM SATSUNAIGAWA DAM
YANAGIYA Keigo; KAKINUMA Takaharu; TAKEDA Atsushi; IZUMI Norihiro
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 70, 4, I_1363, I_1368, Japan Society of Civil Engineers, 2014, [Peer-reviewed]
Japanese, Scientific journal, Vegetation in rivers causes serious problems such as increases in flood risk due to water level rise during flood. Salicaceae trees are dominant on flood plains and sand bars of rivers in cold and snowy Hokkaido. Therefore, it is crucially important to inhibit the growth of salicaceae trees for river management. While there is a problem that salicaceae trees are flourishing in the Satsunai River, one plant species in the family salicaceae, chosenia arbutifolia, is losing its habitat. Chosenia arbutifolia is registered in the red data book of Japan. Hokkaido Development Bureau, the management authority, is performing field experiments to sweep away young salicaceae, and to form fluvial bars covered with gravel by artificial flash flood with the use of snow melting water released from Satsunaigawa Dam. Authors studied the habitat situations of young salicaceae and chosenia arbutifolia before and after an artificial flash flood, and relations between hydraulic conditions and habitat of the plants.

THE SOURCE AREA OF THE TSUNAMIGENIC TURBIDITY CURRENT IN THE GREAT EAST JAPAN EARTHQUAKE
WADA Moemi; IZUMI Norihiro; WATANABE Yasunori
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 70, 4, I_1177, I_1182, Japan Society of Civil Engineers, 2014, [Peer-reviewed]
Japanese, On March 11, 2011, huge tsunamis took place due to the Great East Japan Earthquake as large as Mw 9.0. It has been observed that an ocean bottom presimeter (OBP) and an ocean bottom seismometer (OBS) were sagged to the deep ocean by approximately 1 km, which suggests the possibility of the generation of a large scale line-source turbudity current taking place on the ocean floor off the coast of Tohoku. In this study, we reproduce the tsunami by the use of a tsunami simulation software, iRIC/ELIMO, evaluate the entrainment rate of suspended sediment, and estimate the source area of the turbidity current. It is found, from the results of the analysis, that a large amount of entrainment continuously took place from the north of Oshika Peninsula to the area within 40 km off the coast of Sendai Bay, which is assumed to be the source area of the turbidity current.

カナダ・ブリティッシュコロンビア州の河口デルタ上に見られるサイクリックステップの形態
山本真也; 横川美和; CLARKE John E. Hughes; 泉典洋
堆積学研究, 73, 1, 2014, [Peer-reviewed]

THE EFFECTS OF VELOCITY AND DENSITY PROFILES ON THE ATMOSPHERIC INTERFACE
北野慈和; 山田朋人; 泉典洋
土木学会論文集 B1(水工学), 70, 4, 2014, [Peer-reviewed]

STABILITY OF FREE SURFACE FLOW REVISITED
IZUMI Norihiro; DE LIMA Adriano Coutinho
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 70, 2, I_801, I_806, 公益社団法人 土木学会, 2014, [Peer-reviewed]
Japanese, Scientific journal, Problems on the stability of laminar flow such as Poiseulle flow and boundary layer flow are one of the most traditional problems in the field of fluid mechanics. Though stability of free-surface flow has been studied by a number of researchers, detailed instability diagram illustrating the growth rate of perturbation in the wavenumber-Reynolds number plane has not been obtained so far. In this paper, we perform linear stability analysis of free surface flow by the use of the spectral collocation method with the Chebyshev polynomials and obtain detailed instability diagrams. It is found that the instability diagrams of free-surface flow are characterized by complicated unstable domains compared with those of 2D Poiseulle flow and boundary layer flow.

EXPERIMENTAL STUDY OF RELATIONSHIP BETWEEN BEDROCK ROUGHNESS AND ALLUVIAL COVER
INOUE Takuya; MATSUMOTO Kazuma; SHIMIZU Yasuyuki; IZUMI Norihiro; PARKER Gary; ITO Akashi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 70, 2, I_727, I_734, 公益社団法人 土木学会, 2014, [Peer-reviewed]
Japanese, In bedrock channels, the areal fraction of alluvial cover is generally modeled as a simple function of sediment supply relative to the transport capacity. Other factors are likely to be important, especially the roughness of the underlying bedrock surface. In this study, we report the results of experiments on the interaction between bed roughness and alluvial cover fraction.<br>Our results show that: 1) the areal fraction of alluvial cover is larger when the surface roughness is larger; 2) when bedrock roughness is rough, the cover fraction gradually increases with sediment supply; 3) low-roughness bedrock requires a relatively large sediment supply before any alluvial patch is formed, and as supply increases, rapidly transitions to a fully alluvial channel.

THE EFFECTS OF VELOCITY AND DENSITY PROFILES ON THE ATMOSPHERIC INTERFACE
KITANO Yoshikazu; YAMADA Tomohito; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_871, I_876, 公益社団法人 土木学会, 2014, [Peer-reviewed]
Japanese, Scientific journal, Schmid & Henningson discussed the point disturbance in the homogeneous medium of piecewise linear boundary layer using the method of stationary phase. In addition to this study, we include the density profile to consider the inhomogeneous boundary layer like atmospheric boundary layer. We assume first that the fluid is inviscid and incompressible, density being convected but not diffused. Then the fundamental equations are the Navier-Stokes equations, continuity equation and incompressibility equation and we derive the 3-dimentional Taylor-Goldstein equation. Under the Boussinesq approximation, we obtain the exact solution about the point disturbance propagation on the arbitrary horizontal plane. Using internal Froude number, we explain the characteristics of the solutions.

THE SOURCE AREA OF THE TSUNAMIGENIC TURBIDITY CURRENT IN THE GREAT EAST JAPAN EARTHQUAKE
WADA Moemi; IZUMI Norihiro; WATANABE Yasunori
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_1177, I_1182, 公益社団法人 土木学会, 2014, [Peer-reviewed]
Japanese, On March 11, 2011, huge tsunamis took place due to the Great East Japan Earthquake as large as Mw 9.0. It has been observed that an ocean bottom presimeter (OBP) and an ocean bottom seismometer (OBS) were sagged to the deep ocean by approximately 1 km, which suggests the possibility of the generation of a large scale line-source turbudity current taking place on the ocean floor off the coast of Tohoku. In this study, we reproduce the tsunami by the use of a tsunami simulation software, iRIC/ELIMO, evaluate the entrainment rate of suspended sediment, and estimate the source area of the turbidity current. It is found, from the results of the analysis, that a large amount of entrainment continuously took place from the north of Oshika Peninsula to the area within 40 km off the coast of Sendai Bay, which is assumed to be the source area of the turbidity current.

OBSERVATIONS ON CHARACTERISTICS OF WASHED AWAY OF YOUNG SALICACEAE BY FLASH FLOW FROM SATSUNAIGAWA DAM
YANAGIYA Keigo; KAKINUMA Takaharu; TAKEDA Atsushi; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_1363, I_1368, 公益社団法人 土木学会, 2014, [Peer-reviewed]
Japanese, Vegetation in rivers causes serious problems such as increases in flood risk due to water level rise during flood. Salicaceae trees are dominant on flood plains and sand bars of rivers in cold and snowy Hokkaido. Therefore, it is crucially important to inhibit the growth of salicaceae trees for river management. While there is a problem that salicaceae trees are flourishing in the Satsunai River, one plant species in the family salicaceae, chosenia arbutifolia, is losing its habitat. Chosenia arbutifolia is registered in the red data book of Japan. Hokkaido Development Bureau, the management authority, is performing field experiments to sweep away young salicaceae, and to form fluvial bars covered with gravel by artificial flash flood with the use of snow melting water released from Satsunaigawa Dam. Authors studied the habitat situations of young salicaceae and chosenia arbutifolia before and after an artificial flash flood, and relations between hydraulic conditions and habitat of the plants.

Tsunami-generated turbidity current of the 2011 Tohoku-Oki earthquake
Kazuno Arai; Hajime Naruse; Ryo Miura; Kiichiro Kawamura; Ryota Hino; Yoshihiro Ito; Daisuke Inazu; Miwa Yokokawa; Norihiro Izumi; Masafumi Murayama; Takafumi Kasaya
GEOLOGY, 41, 11, 1195, 1198, Nov. 2013, [Peer-reviewed]
English, Scientific journal

Measurements concerning generation of rhomboid rills in flume experiments: Froude number and sand-topographic feature
Noritaka Endo; Murakami Takashi; Norihiro Izumi
Journal of the Physical Society of Japan, 82, 3, Mar. 2013, [Peer-reviewed]
English, Scientific journal

Vorticity Instabilities in Wave-Breaking Process : Formations of 3D Vortex Structure, Finger Jets and Sea Sprays
WATANABE Yasunori; IZUMI Norihiro; SARUWATARI Ayumi
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 69, 2, 51, 55, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, This paper presents vorticity instabilities occurring during wave breaking process, which interprets formations of the initial three-dimensional vortex structure, scarifying and fingering surface via surface-vorticity interactions, and the sea-spray fragmenting from the finger jets. Three-dimensional linear instability analyses are performed for identifying these instability modes to describe a series of local surface deformations featuring the splashing process in this study.

Rayleigh-Taylor Instability in Porous Media
IZUMI Norihiro; MAEDA Ken-ichi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 69, 2, I_545, I_551, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, Scientific journal, When rain pours over porous media, rain water tends to infiltrate their inside. In order to enable further infiltration, the air in the void of porous media has to be replaced with water. If the replacement between water and air is not smoothly implemented, water cannot seep into porous media as observed on river levees during heavy rainfall. This might be caused by the fact that the equilibrium of water with a relatively high density on top of air with a far lower density may be stable or weakly unstable in porous media. We have performed a linear stability analysis to study the Rayleigh-Taylor instability in porous media.

AN EXPERIMENTAL STUDY OF STEP TOPOGRAPHY ON THE ICE SURFACE
YOKOKAWA Miwa; IZUMI Norihiro; NAITO Kensuke; YAMADA Tomohito; GREVE Ralf
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_1129, I_1134, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, Scientific journal, The spiral troughs observed on the surface of Mars' north polar ice cap show upstream-migrating structures, which indicate that those may possibly be cyclic steps formed by a density current created by cooling of the atmosphere due to the ice. It can be useful to estimate the formative process of the Mars' polar ice cap and thus the climatic history of Mars using the analogues of cyclic steps on the Earth. In this study, we have performed a series of physical experiments aimed at the formation of cyclic steps on ice by flowing fluid. Temperature distribution plays a quite important role for the formation and development of step topography on the ice surface, and was set as ice &lsaquo; fluid &lsaquo; ambient air in this experiment. As a result, step topography was formed on the ice except the case whose Fr is lowest, i.e., 0.76, and the steps generally developed upstream direction. The results of the present experiment agree with the mathematical model describing the evolution of the ice surface by flowing fluid.

DOWNSTREAM MIGRATING STEPS ON ICE
NAITO Kensuke; IZUMI Norihiro; YOKOKAWA Miwa; YAMADA Tomohito
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_1123, I_1128, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, Scientific journal, In recent years, cyclic steps are discovered in a variety of environments, such as deep ocean floors and ice floors on planets other than the earth. Water can exists only in the form of ice in the extraterrestrial environments, where temperature is commonly by far lower than that on the earth. Therefore, cyclic steps in the extraterrestrial environments are expected to be often found on ice. In order to obtain basic knowledge on the formation of ice steps, we have performed a series of experiments in a cold room of Institute of Low Temperature Science, Hokkaido University, and reproduced ice steps migrating in the downstream direction. In this paper, we formulated the formation process of ice steps, and provide a reasonable explanation of the downstream migrating ice steps based on the experimental results.

BOUNDARY INSTABILITY GENERATED ON THE FLOW-ICE INTERFACE
IZUMI Norihiro; YOKOKAWA Miwa; NAITO Kensuke
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_1117, I_1122, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, Scientific journal, Periodic boundary waves are sometimes observed on surfaces of large ice bodies such as glaciers and polar ice caps on Mars as well as on the Earth. These boundary waves may be formed by boundary instability between the ice surface and the fluid flowing on it. We propose a mathematical model to describe the evolution of the ice surface by the use of the Navier-Stokes equations, the heat transfer equations of flow and ice, and a heat balance equation at the boundary. Assuming that the temperature above the flow is higher than that below the ice, we perform a linear stability analysis, and obtained the results that the flow-ice boundary becomes unstable in the range of large Reynolds numbers, and the boundary waves migrate upstream in this temperature condition.

THE BEDLOAD TRANSPORT RATE AND HYDRAULIC RESISTANCE IN BEDROCK CHANNELS PARTLY COVERED WITH GRAVEL
TANAKA Gaku; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_1033, I_1038, 公益社団法人 土木学会, 2013, [Peer-reviewed]
Japanese, Scientific journal, Riverbed degradation occurs in many rivers in the world. It causes serious problems in river management. For example, the bedrock which had been covered with gravels is exposed due to the riverbed degradation, which destabilizes river structures, such as bank revetment works and groundsill works. In this study, hydraulic experiments were performed to determine sediment transport characteristics on bedrock channels partly covered with gravels. We obtained the following results. The bedload transport rate and the friction coefficient can be related with the coverage rate of gravels on the channel bed. A simple mathematical model describing sediment behavior on bedrock channels was proposed.

Linear stability analysis of river meander with gradual bed aggradation/degradation
IZUMI Norihiro; AOKI Akinori
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 68, 2, I_609, I_616, 公益社団法人 土木学会, 2012, [Peer-reviewed]
Japanese, It is commonly observed that river channels become unstable to shift their courses repeatedly particularly when bed aggradation is taking place. On the contrary, river channels are stable and maintain their courses under bed degradation. We study the effect of bed aggradation and degradation on stability of river channels. We perform linear stability analysis of channel meander taking account of gradual bed aggradation and degradation. It is found from the analysis that bed aggradation decreases stability of channels and induce channel meandering while bed degradation stabilize channels and inhibit channel meandering.

CYCLIC STEP MORPHOLOGY FORMED ON BEDROCK
IZUMI Norihiro; YOKOKAWA Miwa; PARKER Gary
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 68, 4, I_955, I_960, 公益社団法人 土木学会, 2012, [Peer-reviewed]
Japanese, In rivers located in mountain areas, a series of steps are often observed to be formed on bedrock. This is called cyclic steps formed by bedrock incision. This study proposes a simplified model for describing the erosion process by abrasion due to bedload, and obtain an equilibrium step shape migrating upstream without changing its shape. It is found that there are three important parameters: the threshold velocity Ut for bedload, the availability function at the Froude critical point pc, and the average slope. Once these three parameters are given, the wavelength L, the erosion rate averaged over one step length En, and the water and bed surface profiles are determined. It is found that qualitative features of steps observed in experiments are well described by the analysis.

The Development of disturbance on the atmospheric density stratification
KITANO Yoshikazu; YAMADA Tomohito J; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 68, 5, I_205, I_210, 公益社団法人 土木学会, 2012, [Peer-reviewed]
Japanese, &nbsp;There are many unknown issues about line-shaped rainbands (LRBs) which is one of the meso-scale meteorological phenomena making torrential rainfall events in Japan. For disaster prevention, it is very important to reveal the formation mechanism of LRBs. In order to know the mechanism, the authors try to examine the instability of the density stratification. In this study, the rainfall and thermodynamic effects are not considered. To simplify the discussion, this theory considers only the up/down motion of the disturbance in the stratified atmosphere. Using this theory, the authors correlate the region of horizontal disturbance and the two parameters which characterize the shape of LRBs, i.e. the Froude number and the rate of density difference.

SCOURING OF SOFT ROCK IMITATED WITH MORTAR BY THE COLLISION OF GRAVEL
KOMATU Yuusuke; WTANABE Yasuharu; IZUMI Norihiro; TAKEBAYASHI Hiroshi
Advances in River Engineering, 17, 67, 167, 172, 公益社団法人 土木学会, Jul. 2011, [Peer-reviewed]
Japanese

INSTABILITY OF FLOW IN OPEN CHANNELS PARTIALLY COVERED WITH VEGETATION
DE LIMA Adriano Coutinho; IZUMI Norihiro
Journal of JSCE, B1(Hydraulic Engineering), 55, ROMBUNNO.32, Feb. 2011, [Peer-reviewed]
English, Scientific journal

PERIODIC CONFIGURATION OF CHANNELS FORMED ON STEEP SLOPES
WUBNEH Atinkut Mezgebu; IZUMI Norihiro
Journal of JSCE, B1 (Hydraulic Engineering), 67, 4, S-127-S-132, Feb. 2011, [Peer-reviewed]
English, Scientific journal

Cyclic steps formed by turbidity currents
DIAS Duleeka Dahampriya; IZUMI Norihiro; YOKOKAWA Miwa
Journal of JSCE, A2 (Applied Mechanics), 67, 2, I_503, I_510, 2011, [Peer-reviewed]
English, Scientific journal

The formation of boundary waves in closed conduits with sediment transported
T. Hiratsuka; N. Izumi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 67, 2, I_671, I_682, 公益社団法人 土木学会, 2011, [Peer-reviewed]
Japanese, Scientific journal, There have been a large number of studies on bed waves in rivers. It has been known that bed waves are strongly related to the Froude number. Meanwhile, there are only few studies on waves formed at the boundary between flowing water and erodible beds in closed conduits without free water surfaces. In order to predict the flow resistance of closed conduits such as sediment bypass tunnels and ice-covered rivers, it is important to obtain detailed information on the formation of boundary waves. Seki and Izumi²⁾ have proposed a linear stability analysis to explain the formation of small scale boundary waves in closed conduits. They have also reproduced small scale boundary waves in flume experiments, and compared with their analysis. According to their analysis, the Shields and Euler numbers are the dominant parameters, and the flat bed becomes unstable when the Euler number becomes larger than the critical Euler number, which increases with the Shields number. However, the agreement between the prediction and their observation is not sufficiently good. In this study, we introduce the ratio of the shear velocities between the lower and upper walls as a new parameter, and improve the agreement. In addition, we perform a weakly nonlinear stability analysis to obtain more detailed information on behavior of boundary waves in the vicinity of the critical Euler number. We find that the transition between flat bed and boundary wave regimes in closed conduits is characterized by subcritical bifurcation.

Linear stability analysis of fluvial bars considering the time variation of bed slopes with aggradation and degradation
T. Takahata; N. Izumi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 67, 2, I_661, I_669, 公益社団法人 土木学会, 2011, [Peer-reviewed]
Japanese, Bed slope changes due to bed aggradation/degradation caused by an increase/decrease of sediment supply. Though we have performed a linear stability analysis of sand bars incorporating effects of bed aggradation/degradation, the analysis has assumed bed elevation changes without changing its shape, and temporal variation of bed slope has not been taken into account. In order to study bar instability with temporal variation of bed slope, the WKB method is applied with the use of the rate of bed slope changes as a small parameter. The analysis shows that, unstable regions in the instability diagram is expanded to the range of large wavenumbers when bed slope decreases while unstable regions are reduced when bed slope increases.

Study on incipient channelization due to seepage erosion
Y. Takei; N. Izumi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 67, 2, I_511, I_519, 公益社団法人 土木学会, 2011, [Peer-reviewed]
Japanese, Scientific journal, Overland and seepage flows have been hypothesized as dominant factors in the initiation and evolution of gullies and channels. Many studies on channelization due to erosion by overland flow have been carried out whereas only few studies have focused on seepage erosion. This study aims to acquire fundamental knowledge on the seepage erosion from experiments and a linear stability analysis. We use the Dupuit-Forchheimer equation and a description of the retreat of the seepage front. The retreat speed consists of two terms: the first is assumed to be a power law function of a specific discharge at the front exceeding a critical discharge, and the second is assumed to be a diffusion-like function of front shapes, in which the retreat speed is enhanced and retarted by the convexity and concavity of fronts, respectively. We find that the characteristic channel spacing becomes infinitely small when the effect of the front shapes is excluded. We conduct a series of experiments with various depth of sediment layers and chamber slopes in order to estimate the diffusion-like coefficient. We find that the width of gullies increases with increasing grain size and bed gradient, while channel spacing decreases. We propose a relationship between the diffusion-like coefficient and the combination of the two functions, water level at the seepage front and weight of a failure block.

LINEAR STABILITY ANALYSIS OF FLUVIAL BARS WITH BED AGGRADATION AND DEGRADATION
TAKAHATA Tomoaki; IZUMI Norihiro
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, S_865-S_870, I_870, 公益社団法人 土木学会, 2011, [Peer-reviewed]
Japanese, In the existing linear stability analysis of fluvial bars, it is assumed that the river bed is in equilibrium, and the bed slope and flow are uniform in the streamwise direction. Though it is generally said that the bed becomes more unstable under bed aggradation, and becomes more stable under bed degradation, the existing analysis cannot shed further light on their effects. In this paper, linear stability analysis incorporating weakly non-equilibrium processes of bed aggradation/degradaion is performed by the use of the WKBJ method in order to clarify their effects. Bed aggradation or degradation is assumed to be sufficiently slow compared with the bed evolution due to instability, and its non-dimensional speed is used as a small parameter. The analysis explains that river beds become stable and sand bars tend not to be formed under degradation, and that river beds become unstable under aggradation. In addition, alternate bars are more strongly affected by bed aggradation/degradation than multiple bars.

Instability of shallow open channel flow with lateral velocity gradients
A. C. Lima; N. Izumi
13TH EUROPEAN TURBULENCE CONFERENCE (ETC13): INSTABILITY, TRANSITION, GRID TURBULENCE AND JETS, 318, SECTION 3, 2011, [Peer-reviewed]
English, International conference proceedings

Inception of stream incision by seepage erosion
A. Pornprommin; N. Izumi
Journal of Geophysical Research: Earth Surface, 115, 2, F02022, Blackwell Publishing Ltd, 01 Jun. 2010, [Peer-reviewed]
English, Scientific journal

Inception of stream incision by seepage erosion
A. Pornprommin; N. Izumi
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 115, doi: 10.1029/2009JF001369, Jun. 2010, [Peer-reviewed]
English, Scientific journal

Channel inception in cohesionless sediment by seepage erosion
Adichai Pornprommin; Yoshihiro Takei; Atinkut Mezgebu Wubneh; Norihiro Izumi
JOURNAL OF HYDRO-ENVIRONMENT RESEARCH, 3, 4, 232, 238, Mar. 2010, [Peer-reviewed]
English, Scientific journal

The formation of boundary waves in closed conduits without free water surfaces
T. Hiratsuka; N. Izumi; Y. Seki
Annual Journal of Hydraulic Engineering, 54, 151, 156, Feb. 2010, [Peer-reviewed]
Japanese, Scientific journal

EXPERIMENTS ON CHANNEL INCEPTION BY SURFACE RUNOFF
WUBNEH Atinkut Mezgebu; PORNPROMMIN Adichai; IZUMI Norihiro; NAGAHARA Junya
Annual journal of Hydraulic Engineering, JSCE, 54, 151, 156, Feb. 2010, [Peer-reviewed]
English, Scientific journal

Experiments on the gully development due to seepage erosion
Y. Takei; A. Pornprommin; N. Izumi
Journal of Applied Mechancs, JSCE, 13, 883, 888, 2010, [Peer-reviewed]
Japanese, Scientific journal

Stability Analysis of Fluvial Bars Using a New Bed Load Formula
PORNPROMMIN Adichai; IZUMI Norihiro
Journal of Applied Mechancs, JSCE, 13, 877, 882, 2010, [Peer-reviewed]
English, Scientific journal

Numerical simulation of channelization by seepage erosion
PORNPROMMIN Adichai; TAKEI Yoshihiro; WUBNEH Atinkut Mezgebu; IZUMI Norihiro
Journal of Applied Mechancs, JSCE, 12, 887, 894, 土木学会, Aug. 2009, [Peer-reviewed]
English, Scientific journal

Channelization on plateaus with arbitrary shapes
A. Pornprommin; N. Izumi; T. Tsujimoto
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 114, F01032, doi:10.1029/2008JF001034, Mar. 2009, [Peer-reviewed]
English, Scientific journal

The bifurcation pattern of the flat bed and antidune transition
N. Izumi; G. Parker
Annual journal of Hydraulic Engineering, JSCE, 53, 139, 144, Feb. 2009, [Peer-reviewed]
Japanese, Scientific journal

LINEAR STABILITY ANALYSIS OF ESCARPMENT PLANFORMS BY GROUNDWATER SAPPING
PORNPROMMIN Adichai; IZUMI Norihiro
Annual journal of Hydraulic Engineering, JSCE, 53, 139, 144, Feb. 2009, [Peer-reviewed]
English

Theoretical analysis for the interaction between the river flow and the seepage flow
Upaka Rathnayake; Norihiro Izumi
RECENT ADVANCES IN FLUID MECHANICS, 46, 51, 2009, [Peer-reviewed]
English, International conference proceedings

Experimental study of channelization by seepage erosion
Pornprommin Adichai; Norihiro Izumi
Journal of Applied Mechanics, JSCE, 11, 709, 717, 土木学会, 2008, [Peer-reviewed]
English, Scientific journal

The effect of pressure gradient on the dune-flat bed transition
IZUMI Norihiro; SATO Hiroshige
Journal of Applied Mechanics, JSCE, 11, 851, 857, 公益社団法人 土木学会, 2008, [Peer-reviewed]
Japanese, Scientific journal, The effect of pressure gradient on the dune-flat bed transition is studied in terms of linear and weakly nonlinear stability analysis. We employ the Kovacs & Parker bedload transport formula extended to incorporate the effect of pressure gradient on the lee side of dunes proposed by Yamaguchi & Izumi.The linear anlysis reveals that the critical Froude number is slightly increased due to the effect of pressure gradient. The nonlinear stability analysis reveals that the effect of pressure gradient renders the bifurcation pattern at the dune-flat bed transition subcritical in the range of relatively large resistance coefficients.

Stability of sand-water boundary in pipes
SEKI Yohei; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 11, 753, 760, 公益社団法人 土木学会, 2008, [Peer-reviewed]
Japanese, Scientific journal, It is commonly known that the flat bed is unstable in open channels in the range of small and large Froude numbers, in which the presence of the free water surface is important to the instability. However, instability of the flat bed without free water surface has not been well understood. In this study, we perform a linear stability analysis of the boundary between sediment and water in pipes transporting sediment with the use of the mixing length turbulent model. The analysis reveals that the governing parameter is the Euler number, and that the boundary is unstable in the range of relatively small Euler numbers.

Linear stability analysis of small-scale fluvial bed waves with active suspended sediment load
NAKASATO Yosuke; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 11, 727, 734, 公益社団法人 土木学会, 2008, [Peer-reviewed]
Japanese, Scientific journal, Small-scale fluvial bed waves such as dunes and antidunes formed on river beds during floods increase the bed resistance, causing rises in water levels. Therefore, it is important to obtain detailed information on the conditions for the formation of bed waves. One of the purposes of this study is to extend the existing linear stability analysis of the formation of small-scale bed waves to the case with active suspended sediment transport. The analysis reveals that the critical Froude number for the formation of dunes is reduced, and the dune formation tends to be inhibited with increasing suspended sediment load.

The effects of non-equilibrium sediment transport process on instability of dune formation
S. Yamaguchi; N. Izumi
Annual journal of Hydraulic Engineering, JSCE, 51, 1015, 1020, Feb. 2007, [Peer-reviewed]
Japanese, Scientific journal

THE EFFECTS OF NON-EQUILIBRIUM SEDIMENT TRANSPORT PROCESS ON INSTABILITY OF DUNEFORMATION
YAMAGUCHI Satomi; IZUMI Norihiro
Doboku Gakkai Ronbunshuu B, 51, 1015, 1020, Japan Society of Civil Engineers, 2007, [Peer-reviewed]
Japanese, Scientific journal, In order to enable accurate predictions of the formation of dunes, to predict the effect of non-equilibrium sediment transport process is important. The stochastic model has been known to be the non-equilibrium sediment transport formula which can describe the sediment transport lag behind the bed shear stress. In this study, we performed a linear stability analysis by the use of the stochastic model with the two dimentional Reynolds equations. The phase lag between the sediment transport and bed shear sterss is generated from step length on the sediment transport process, and the phase lag between the shear stress and flow velocity is generated from the fluid viscosity. The two phase lags are able to be theoretically predicted in this analysis. It is found that the instability of dune formation is shown by the balance of the two phase lags. We also performed a weakly nonlinear analysis. It is found that the dune-flat bed transition is charactrized by the subcritical bifurcation in the range of small bed slop and small step length.

The formation of submarine gullies on continental shelves with arbitrary shapes by turbidity currents
YAMAGUCHI Kenji; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 10, 865, 872, 公益社団法人 土木学会, 2007, [Peer-reviewed]
Japanese, Scientific journal, Patterns of parallel submarine gullies with regular transverse spacing are observed at continental margins. These gullies are thought to be formed by turbidity currents. In this study, the existing model is extended to more general cases in which the slope profile is arbitrary and the entrainment of fresh seawater cannot be neglected. A linear stability analysis is performed with the use of the layer-averaged momentum and continuity equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents. The analysis shows that the dominant spacing of submarine gullies on slopes with arbitrary shapes is of the order of 800-1600 times the Richardson-critical layer thickness of turbidity currents.

On stability between river flow and seepage flow
OHTOMO Hirotaka; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 10, 833, 838, 公益社団法人 土木学会, 2007, [Peer-reviewed]
Japanese, Scientific journal, The instability of water flow has been studied by a large number of researchers from a variety of points of view for a long time. In this study, a linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law extended to more general cases in order to investigate the instability of flow on permeable river beds, and resulting water exchange between flowing water in rivers and seepage water beneath flat river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found from the analysis that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds.

WEAKLY NONLINEAR STABILITY ANALYSIS OF FLUVIAL DUNES BY THE USE OF THE MIXING LENGTH TURBULENT MODEL
Norihiro Izumi; Kazuyoshi Hasegawa
Annual journal of Hydraulic Engineering, JSCE, 51, 1021, 1026, 公益社団法人 土木学会, 2007, [Peer-reviewed]
Japanese, Scientific journal, Weakly nonlinear stability analysis of fluvial dunes is performed with the use of the growth rate expansion method incorporated with the multiple scale parturbation technique. Open channel flow is modeled by the mixing length turbulent model. A series of perturbation equations are solved by the use of spectral collocation method with Chebyshev polynomial. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation when the resistant coefficient C<SUP>-</SUP><SUP>1</SUP> is large.

Application of old maps for studying long term shoreline change
Tanaka, H; Takahashi, G; Matsutomi, H; Izumi, N
Proceedings of 30th International Conference on Coastal Engineering, 4022, 4034, Sep. 2006, [Peer-reviewed]
English, International conference proceedings

Channelization on plateaus composed of weakly cohesive fine sediment
N. Izumi; K. Fujii
Journal of Geophysical Research: Earth Surface, 111, 1, Blackwell Publishing Ltd, 24 Mar. 2006, [Peer-reviewed]
English, Scientific journal

Channelization on plateaus composed of weakly cohesive fine sediment
N Izumi; K Fujii
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 111, F1, doi:10.1029/2005JF000345, Feb. 2006, [Peer-reviewed]
English, Scientific journal

THE PROCESSES OF GULLY DEVELOPMENT AND SEDIMET YIELD
MIZUSHIMA Hiroki; IZUMI Norihiro
ANNUAL JOURNAL OF HYDRAULIC ENGINEERING, JSCE, 50, 1051, 1056, 公益社団法人 土木学会, Feb. 2006, [Peer-reviewed]
Japanese, Scientific journal, Surface flow produced by heavy rainfall concentrates on local troughs, resulting in further erosion of troughs and the formation of gullies. In the development process of gullies, a great amount of soil runs off. In this study, long-term changes of topography around gullies formed on Soya Hill are analysed with the of present and old topographical maps. In the analysis, detailed processes of gully development are revealed, and the annual average sediment yield is estimated to be 60 mm/year. We also conduct a field observation of a gully and a field survey around the gully head. It is found that the channel head is in the precess of spliting into three branches.

Weakly nonlinear analysis of dunes by the use of a sediment transport formula incorporating the pressure gradient
Satomi Yamaguchi; Norihiro Izumi
River, Coastal and Estuarine Morphodynamics: RCEM 2005 - Proceedings of the 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2, 813, 820, 2006
English, International conference proceedings

THE DUNE-FLAT BED TRANSITION REVISITED
IZUMI Norihiro; YAMAGUCHI Satomi
Journal of JSCE, B, 62, 4, 360, 375, 公益社団法人 土木学会, 2006, [Peer-reviewed]
Japanese, Scientific journal, Hysteresis is known to arise in stage-discharge relations of flow in streams with movable beds. In certain cases, the hysteresis is caused by the transition of riverbed forms between dune and flat bed regimes. From a large number of field and experimental data, it is commonly said that the resistance relation is a multivalued function of hydraulic parameters because two different bed forms can appear alternatively under a single hydraulic condition. The authors have proposed a mathematical model to provide a physical explanation for the hysteresis arising in stage-discharge relations due to the dune-flat bed transition, and two different bed forms appearing alternatively under a single hydraulic condition. They performed a weakly nonlinear stability analysis with the use of the growth rate expansion method incorporated with a multiple-scale perturbation technique, and showed that the dune-flat bed transition is characterized by subcritical bifurcation. In this paper, a similar analysis is performed without approximations employed in the previous analysis. We also take into account an appropriate dependency between the Froude and Shields numbers. In addition, we redefine the Froude number as a bifurcation parameter, and reevaluate experimental data in order to validate the analysis. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation in the range of small average bed slopes and large velocity coefficients. A comparison between experimental data and the result of the analysis show a good agreement in that two different bed forms can appear alternatively under a single hydraulic condition at least in the range of large velocity coefficients.

EVALUATING OF LONG-TERM SHORELINE CHANGE BY USING OLD MAPS
TAKAHASHI Genki; TANAKA Hitoshi; MATSUTOMI Hideo; IZUMI Norihiro
PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN, 22, 451, 456, 公益社団法人 土木学会, 2006, [Peer-reviewed]
Japanese, Scientific journal, Old maps, such as <I>Inoh Maps</I> and other historical ones, are prospective which might be used for determining the changes of coastal geographical features in the past. It is expected that long-term geographical changes can be known provided that the accuracy of an old map is satisfactorily high. In the present study, the changes of geographical features in Nobiru Coast, Miyagi Prefecture and Matsukawaura Lagoon, Fukushima Prefecture are examined by comparing historical and latest maps. Furthermore, long-term sediment budget analysis is carried out for the Nobiru Coast.

The behavior of turbidity currents flowing down from continental shelves to continental slopes
YAMAGUTI Kenji; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 9, 925, 932, 公益社団法人 土木学会, 2006, [Peer-reviewed]
Japanese, Scientific journal, A mathematical model of turbidity currents flowing down from continental shelves to continental slopes is presented in this study. The layer-averaged momentum and continuity equations of turbidity currents, and the dispersion equation of suspended sediment are integrated with the use of a regularity condition satisfied at the Richardson critical point between continental shelves and continental slopes. The results of the analysis show that steady turbidity currents flowing from continental shelves to continental slopes can be realized only when the critical layer thickness is smaller than a certain value. It is also found that turbidity currents are mildly accelerated on continental slopes while turbidity currents are decelerated on continental shelves in the downstream direction. These results suggest that only turbidity currents with sufficiently large suspended concentration can reach the Richardson critical point, and that turbidity currents flowing from continental shelves to continental slopes have to be generated somewhere not far upstream from the Richardson critical point.

Stability of shallow water flow on permeable beds
OHTOMO Hirotaka; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 9, 893, 900, 公益社団法人 土木学会, 2006, [Peer-reviewed]
Japanese, Scientific journal, The instability of shallow water flow has been studied by a large number of researchers from a variety of viewpoints since a long time ago. It has been found from linear stability analysis that, when the Froude number is large, uniform flow becomes unstable, resulting in the evolution of a train of waves, which are called roll waves. In this study, a linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and the Darcy's equation extended in order to investigate the instability of flow on permeable river beds. From the analysis, we conclude that the stability of the flow becomes unstable when the wavenumber is from 0.02 to 0.2 and high Froude number. Furthermore, it is found that flow becomes unstable in the range of wavenumber from 0.02 to 0.2 with decreasing permeable layer thickness and with increasing permeation.

LINEAR STABILITY ANALYSIS OF CHANNEL INCEPTION ON SLOPES WITH ARBITRARY SHAPES
IZUMI Norihiro; PORNPROMMIN Adichai; TSUJIMOTO Tetsuro
JOURNAL OF JSCE, B, 62, 1, 65, 79, 公益社団法人 土木学会, 2006, [Peer-reviewed]
Japanese, Scientific journal, The existing theories of channel formation by surface sheet flow assume self-preserving base state slope profiles which migrate upstream without changing their shapes because formal stability analysis becomes inpossible if base state slope profiles are in unsteady states. In this study, the theories of Izumi and Parker²⁾, and Izumi and Fujii³⁾ are extended to include the case of channelization on slopes with arbitrary shapes with the use of the "frozen time approach" and the "momentary stability concept". In the frozen time approach, time derivative terms of base state equations are dropped under the assumption that the growth of perturbations is sufficiently faster than the evolution of base states as a first approximation. The stability of unsteady base states is further studied in terms of the momentary stability concept in which base states are assumed to become unstable for perturbations if the growth of perturbations is faster than the evolution of base states.<BR>The analysis shows that, as long as their curvatures lie in appropriate ranges, slopes become unstable to evolve into slopes incised by channels, the spacing of which is on the order of one thousand times the depth of surface sheet flow. In the erosion-dominant case such as chennelization on slopes composed of strongly cohesive soils, the spacing between incipient channels are slightly decreased with increasing slope curvatures. In the range of sufficiently large curvatures, slopes are momentarily stable as the evolution rate of base states surpasses the growth rate of perturbations. In the case that both erosion and deposition are significant such as channelization on slopes composed of weakly cohesive soils, slopes with small curvatures are found to be unstable though clear dominant channel spacing does not appear. In the range of sufficiently large curvatures, slopes tend to be momentarily stable as well as in the erosion-dominant case.

THE TRANSITION BETWEEN DUNE-COVERED AND FLAT BEDS WITH ACTIVE SUSPENDED LOAD
YAMAGUCHI Satomi; IZUMI Norihiro
Journal of JSCE, 796, 53, 67, 公益社団法人 土木学会, Aug. 2005, [Peer-reviewed]
Japanese, Scientific journal, During floods, dunes formed under the condition of a low discharge disappear when the discharge becomes larger than a certain amount, and dunes are re-created with decreasing discharge. On the dune-flat bed transition, it is observed that a critical discharge from dune to flat bed regimes is larger than a discharge from flat bed to dune regimes (hysteresis). The authors have shown that the dune-flat bed transition is characterized by subcritical bifurcation that causes hysteresis with the use of a nonlinear stability analysis. However, the critical Froude number at the dune-flat bed transition predicted in the analysis is much larger than that observed in the field. In this study, we performed a weakly nonlinear analysis incorporated with suspended sediment transport. It is found that the critical Froude number decreases due to the effects of suspended load while the transition is still characterized by subcritical bifurcation.

The formation of channel networks (Flow and Geomorphology)
IZUMI Norihiro
Journal of Japan Society of Fluid Mechanics, 24, 1, 5, 14, 日本流体力学会, Feb. 2005, [Invited]
Japanese

ON CHANNEL BIFURCATION
IZUMI Norihiro
PROCEEDINGS OF HYDRAULIC ENGINEERING, 49, 979, 984, 公益社団法人 土木学会, 2005, [Peer-reviewed]
Japanese, Scientific journal, Channels are commonly observed to develope upstream due to the concentration of flow and the resultant intensification of erosion around their channel heads. In the developing process, a channel head sometimes splits into two or more than two branches. By repeating such bifurcation, simple patterns of channels evolve into comlex patterns of channel networks. In this study, a mathematical model of channel bifurcation is presented in terms of the secondary instability of a channel head. Linear stability analysis is performed to study the instability of a hole in a horizontal plane imitating a channel head. It is found that a channel head becomes unstable for perturbation and chanel bifurcation is initiated when the critical depth divided by the friction coefficient is reduced compared with the channel radius.

Nonlinear stability analysis of dunes by the use of a sediment transport formula including the effect of the pressure gradient
YAMAGUCHI Satomi; IZUMI Norihiro
PROCEEDINGS OF HYDRAULIC ENGINEERING, 49, 937, 942, 公益社団法人 土木学会, 2005, [Peer-reviewed]
Japanese, Scientific journal, In order to enable accurate predictions of the bedform change in rivers, the accurate estimation of the sediment transport rate is important. In this study, we propose a bedload formula taking into account the effect of the pressure gradient in flow caused by the formation of dunes on the basis of Kovacs & Parker's formula including the effect of the local bed inclination. We performed a nonlinear stability analysis by the use of the sediment transport formula derived in this study. It is found that the transition between dune-covered and flat bed transition is charactrized by subcritical bifurcation even if the effect of the local bed inclination is large.

A TRANSPORT MODEL OF FINE SUSPENDED PARTICLES CONSIDERING THE AVAILABILITY ON THE BED
IZUMI Norihiro; PILAILAR Sitang; TANAKA Hitoshi
PROCEEDINGS OF HYDRAULIC ENGINEERING, 49, 907, 912, 公益社団法人 土木学会, 2005, [Peer-reviewed]
Japanese, Scientific journal, The understanding of the transport process of suspended fine particles in rivers becomes important from a viewpoint of biological environment in rivers. In this study, we propose a new transport model of suspended fine particles in rivers considering the availability of fine sediment on the bed. An availability function of fine sediment on the bed is introduced to take into account the reduction of the entrainment rate through lack of fine sediment on the bed. In a sample calculation with the assumption that the flow is in the unsteady normal flow condition, it is shown that the model can delineate an important fact that the SS concentration increases only up to some limit even if the bed shear stress increases. In addition, we applied the model to a field observation and show that the model can describe an important feature that the SS concentration is higher at the begining of a flood and decreases afterward despite large discharge.

古地図を用いた仙台海岸・石巻海岸の長期汀線変動に関する検討
田中 仁; 松冨 英夫; 泉 典洋
海岸工学論文集, 52, 556, 560, 公益社団法人 土木学会, 2005, [Peer-reviewed]
Japanese, Scientific journal, 伊能図は今から約200年ほど前に伊能忠敬により作成され, 我が国全域を網羅する我が国初の本格的な地図として現在でも大きな関心を集めている. 伊能図に関してはこれまで人文地理の視点から注目を集めることが多かったが, その精度が定量的検討に耐えうるほど十分であれば, 海岸地形・河川地形の研究分野においても, 200年以上も前の地形情報を与えるものとして貴重な存在であると期待される. 本研究では, 阿武隈川や北上川といった比較的大規模な河川が流入している仙台海岸, 石巻海岸を対象とし, 伊能図 (大図) に描かれた海岸地形について, 現在のそれとの相違に着目して考察を行った.

On the instability of shallow water flow on permeable beds
OHTOMO Hirotaka; IZUMI Norihiro
Journal of Applied Mechanics, JSCE, 8, 813, 820, 公益社団法人 土木学会, 2005, [Peer-reviewed]
Japanese, Scientific journal, The instability of shallow water flow has been studied since a long time ago. It has been found from linear stability analysis that, when the Froude number is larger than approximately two, uniform flow becomes unstable, resulting in the evolution of a terrain of waves, which are called roll waves. In this study, a linear stability analysis is performed with the use of the shallow water equation extended for flow on permeable beds in order to investigate the instability of flow on permeable river beds and the resulting water exchange between river flow and the seepage flow beneath the beds. The analysis reveals that flow is unstable in the range of sufficiently large wavenumbers and Froude numbers when the permeable layer is sufficiently thicker than the flow on the bed. In the range of instability, water exchange between river flow and the hyporheic layer beneath river beds is expected to be activated.

The formation of submarine gullies by turbidity currents
N Izumi
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 109, C3, Mar. 2004, [Peer-reviewed]
English, Scientific journal

WEAKLY NONLINEAR ANALYSIS OF MULTIMODAL FLUVIAL BARS.
PORNPROMMIN A; IZUMI N; TSUJIMOTO T
PROCEEDINGS OF HYDRAULIC ENGINEERING, 48, 2, 1009, 1014, Feb. 2004, [Peer-reviewed]
English, Scientific journal

EFFECTS OF HYDROLOGIC FLUCTUATIONS ON THE TRANSPORT OF FINE PARTICULATE ORGANIC MATTER IN THE NANAKITA RIVER.
PILAILAR S; SAKAMAKI T; HARA Y; IZUMI N; TANAKA H; NISHIMURA O
PROCEEDINGS OF HYDRAULIC ENGINEERING, 48, 2, 1519, 1524, Feb. 2004, [Peer-reviewed]
English, Scientific journal

Experiments of the step formation on purely erosional beds
SHIMADA Norikazu; IZUMI Norihiro
PROCEEDINGS OF HYDRAULIC ENGINEERING, 48, 967, 972, 公益社団法人 土木学会, 2004, [Peer-reviewed]
Japanese, Scientific journal, Steep channels with purely erosional beds are characterized by a series of steps formed on beds. In this paper, experiments were performed in order to study the formation and the evolution of the steps. In the experiments, the wavelength of steps were found to be of the order of ten to sixty times the initial flow depth before the formation of steps. It was observed that the wavelengths reduced over time. In order to investigate the inception of steps, a linear stability analysis is performed with the use of the spectral method with the Chebyshev polynomial. The experimental results were compared with the theoretical results derived from a linear stability analysis. The agreement between theory and experiments were found to be good.

Linear stability analysis of channel inception on slopes with arbitrary shapes:purely erosional case
PORNPROMMIN Adichai; IZUMI Norihiro; TSUJIMOTO Tetsuro
Journal of applied mechanics, 7, 2, 997, 1004, 公益社団法人 土木学会, 2004, [Peer-reviewed]
Japanese, Scientific journal, The existing linear stability analysis of incipient channelization was limited to the case of self-preserving slope profiles. In this study, the theory is extended to include the channelization on slopes with arbitrary shapes under the assumption that the growth of perturbation is sufficiently faster than the evolution of base state slope profiles; thus, a time derivative term in base state equations is neglected in the linear level (frozen time approach). As the result of a momentary stability analysis, the dominant wavelength is found to decrease with increasing curvature of slopes. In addition, the analysis shows the possibility of channelization even in the case of arbitrary slope profiles.

Beach cusps formed by waves with their crests parallel to the shoreline
TANIKAWA Asako; IZUMI Norihiro; TANAKA Hitoshi
Journal of applied mechanics, 7, 2, 1005, 1012, 公益社団法人 土木学会, 2004, [Peer-reviewed]
Japanese, Scientific journal, Beach cusps are uniformly spaced, arcuate scallops formed at beaches. They are inseparably connected with nearshore currents. The nearshore current system forms a variety of circulation patterns, which have been attracting many researchers' interest since long time ago. While several theories have been proposed on the formation of nearshore current systems, Hino attributed their formation to the dynamic instability, and explained it in terms of linear stability analysis. In this study, his theory is revisited and improved in several aspects.

THE DEVELOPMENT PROCESS OF ROLL WAVES
IGARASHI Akira; IZUMI Norihiro; HOSODA Takashi
PROCEEDINGS OF HYDRAULIC ENGINEERING, 48, 493, 498, 公益社団法人 土木学会, 2004, [Peer-reviewed]
Japanese, Scientific journal, Uniform flow on a relatively steep channel is known to be unstable to evolve into a wave train, which is termed roll waves. Though roll waves have long been studied, their wavelength cannot be theoretically determined. In this study, a linear stability analysis on the wavelength of fully-developed roll waves is performed. It is found that the instability of the fully-developed roll waves is maximized when the wavelength is 0.1-1, and roll waves with infinitely long or infinitesimally short wavelengths are neutrally stable. In order to study the development of roll waves and to verify the theory, numerical simulation is performed. As the distance from the inlet increase, roll waves tend to increase in the wavelength, and to approach a constant wavelength asymptotically.

The characteristic change of fine particulate organic matter due to a flood in the Nanakita river.
PILAILAR S; SAKAMAKI T; IZUMI N; TANAKA H; NISHIMURA O
PROCEEDINGS OF HYDRAULIC ENGINEERING, 47, 1033, 1038, Japan Society of Civil Engineers, Feb. 2003
English, Scientific journal, Sediment sampling was conducted at three locations before and after a flood in the Nanakita river. The sediment samples were analyzed to obtain the information on the particle size distribution, the amount of resuspendable fine particulate organic matter (FPOM) available on the bed, and the composition of the basic nutrients, carbon, nitrogen and phosphorous, in the FPOM. The data suggest that there is an equilibrium state in which the amount of FPOM on the bed is constant in the low flow condition. The behavior of FPOM is found to show strong locality; the amount of FPOM on the bed increases during floods at some locations while it decreases during floods at other locations. In the analysis of nutrients and the microscopic observation, it is suggested that FPOM accumulated on the bed during floods is directly originated from the terrestrial area. FPOM that accumulated in the sediment after flood at all locations are found to be gradually changed in size and composition because biological activities are in process and dominant in the low flow condition.

Stability of bedload-dominated alluvial deltas.
PORNPROMMIN A; IZUMI N; TSUJIMOTO T
PROCEEDINGS OF HYDRAULIC ENGINEERING, 47, 697, 702, Japan Society of Civil Engineers, Feb. 2003, [Peer-reviewed]
English, Scientific journal, A linear stability analysis of the channel inception on bedload-dominated alluvial deltas is performed with the use of the shallow-water equations and the Exner equation. At the downstream end of a delta i. e. the delta front, there is a body of standing water, where water surface elevation of the water body controls the flow depth at the delta front. The bedload transported beyond the front is accumulated on the slope at the front, which causes the migration of the delta front. Upward-concave bed profile is found in the one-dimensional base state. In the two-dimensional linear stability analysis, only negative growth rate is found in all the cases. The absolute value of the growth rate increases with increasing the height of delta front, which implies that deltas with smaller height of delta front are more stable. It is concluded that bedload-dominated alluvial deltas are always stable. This result corresponds to the fact that fan deltas are formed if sediment is sufficiently coarse so that bedload is predominant.

INCEPTIVE TOPOGRAPHY OF FLUVIAL-DOMINATED RIVER MOUTH TERRACES: EXPERIMENTS
IZUMI Norihiro; TANAKA Hitoshi; TSUBOI Kousuke; DATE Masanao
Doboku Gakkai Ronbunshu, 2003, 740, 109, 120, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, Laboratory experiments of river mouth jets were performed to investigate the profiles of velocity and suspended sediment concentration, and the inceptive topography of fluvial-dominated river mouth terraces. The experimental results were found to show reasonably good agreement with the theory proposed by some of the authors. The experiments revealed that the sediment deposits on both sides of the jet axis if the suspended load is dominant, which had been predicted by the theory. It was shown in the experiments that river mouth terraces develop into elongate deltas under the condition of dominant suspended load, which appeared to be definitely different from deltas formed under the condition of dominant bedload.

INCEPTIVE TOPOGRAPHY OF FLUVIAL-DOMINATED RIVER MOUTH TERRACES: THEORY
IZUMI Norihiro; TANAKA Hitoshi; DATE Masanao
Doboku Gakkai Ronbunshu, 2003, 740, 95, 107, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, A mathematical model is presented to describe the formation of river mouth terraces in this paper. The spatial distributions of velocity and suspended sediment concentration are obtained by the use of the integration method and the similarity assumption of lateral profiles of velocity and suspended sediment concentration. The inceptive topography of river mouth terraces are then obtained from the velocity and sediment concentration distributions. It is found that the sediment deposits on both sides of the jet axis when the suspended load is dominant and the effect of advection and diffusion is relatively small, while it deposits on the axis when the bedload is dominant.

SUBCRITICAL BIFURCATION OBSERVED IN THE TRANSITION BETWEEN DUNE AND FLAT BED REGIMES
YAMAGUCHI Satomi; IZUMI Norihiro
Doboku Gakkai Ronbunshu, 2003, 740, 75, 94, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, In the transition process of dune formation, a hysteresis is observed between flow depth and discharge, which is analogous to the multiple-valued relations between the total Shields stress and the effective Shields stress found in experiments. In this study, a weakly nonlinear stability analysis is performed in order to provide a theoretical explanation for the hysteresis observed in the transition of dunes. The growth rate expansion method is used to derive a nonlinear amplitude equation, which shows that when the average bed slope is large and the effect of the local bed inclination is small, the transition of dune formation is characterized by the subcritical bifurcation. This implies that the hysteresis is caused by the subcritical bifurcation.

EXPERIMENTAL STUDY ON THE TRNSITION PROCESS OF DUNES
YAMAGUCHI Satomi; IZUMI Norihiro; IGARASHI Akira
PROCEEDINGS OF HYDRAULIC ENGINEERING, 47, 613, 618, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, The transition process of dune formation is known to be characterized by the hysteresis that the critical Froude number for dunes to disappear with increasing discharge is larger than that to reappear with decreasing discharge. In this study, the experiments on the transition process of dune formation were performed with an experimental flume. After the discharge was gradually increased until dunes disappear, it was gradually decreased until the dunes reappear. The hysteresis was observed in the transition process of dune formation. The results of the experiments are found to be reasonably well explained by the weakly nonlinear stability analysis of dune formation performed by the first and second authors.

RIVER BED CHARACTERISTICS AND THEIR CHANGE OF THE NATORI RIVER
TANIKAWA Asako; IZUMI Norihiro; TANAKA Hitoshi
PROCEEDINGS OF HYDRAULIC ENGINEERING, 47, 607, 612, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, In the alluvial reach of the Natori river, two distinctive morphological features can be seen. The reach from the upstream of Taihaku bridge to the confluence with the Hirose river is characterized by unstable, braided configuration while the reach downstream of the confluence is rather stable. This study provides a theoretical explanation for the distinctions between two reaches in a same river by the use of the theories of stable channel cross-section of straight gravel and sand-silt rivers, and the theory of bar formation. The differences of grain size and bed slope are found to cause such a contrast.

LINEAR STABILITY ANALYSIS OF THE CHANNELIZATION ON SLOPES COMPOSED OF WEAKLY COHESIVE FINE MATERIAL
IZUMI Norihiro; FUJII Kenji
Doboku Gakkai Ronbunshu, 2003, 747, 95, 109, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, This paper presents a mathematical model of the formation of gullies on slopes composed of material with relatively weak cohesivity such as freshly deposited volcanic ash. A linear stability analysis is performed with the use of the momentum equations of flow, the dispersion equation of suspended sediment, and the Exner equation extended for beds subject to erosion and deposition of sediment. The analysis shows that the dominant gully spacing is 600-1500 times the Froude-critical depth of the sheet flow on the slope. Evaluating the critical depth to be 5cm, the spacing of gullies is 30-75m, which is cosistent with observations.

Linear stability analysis of the gully formation on steep slopes
IZUMI Norihiro
Journal of applied mechanics, 6, 959, 966, 公益社団法人 土木学会, 2003, [Peer-reviewed]
Japanese, Scientific journal, A mathematical model of the channelization on steep slopes is presented in this study. A linear stability analysis is performed with the use of the shallow water equations and the Exner equation extended for purely erosional beds. The analysis is found to be similar to that for channelization on mild slopes that the author has presented. The characteristic wavelength associated with the maximum growth rate is of the order of ten times the Froude-critical depth divided by the bed resistance coefficient. The resistance coefficient is estimated of the order of 0.01; thus, the dominant channel spacing is of the order of 1000 times the Froude-critical depth.

Weakly Nonlinear Analysis of Bars with the Use of the Amplitude Expansion Method.
IZUMI Norihiro; PORNPROMMIN Adichai
Doboku Gakkai Ronbunshu, 2002, 712, 73, 86, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, The application of the existing weakly nonlinear theories of sand bars with the use of the growth rate expansion method, in which the growth rate of perturbations is taken as a small parameter for expansion, is limited to the vicinity of the minimum critical aspect ratio (width/depth); the theory is only applicable to the case of alternate bars. In this study, weakly nonlinear analysis with the use of the amplitude expansion method, in which the amplitude of perturbations is taken as a small parameter for expansion, is presented in order to extend theories to the case of multiple bars. It is shown that the reasonably good agreement between experimental and theoretical results of bar wavelength and height.

Theory of the Formation of Submarine Canyons Due to Turbidity Currents.
IZUMI Norihiro
Doboku Gakkai Ronbunshu, 2002, 712, 45, 56, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, A mathematical model of the formation of submarine canyons due to turbidity currents is presented in this study. A linear stability analysis is performed with the use of the momentum equations of turbidity currents, the dispersion equation of suspended sediment, and the Exner equation extended for sea beds subject to erosion due to turbidity currents. The analysis shows that the dominant channel spacing is of the order of 1500-8000 times the Richardson-critical layer thickness of turbidity currents. Evaluating the Richardson-critical thickness is of the order of 0.1-1.0m, the spacing of young canyons is of the order of 150-8000m. The theoretical results are found to agree resonably well with the observation.

野蒜海岸を中心とする石巻湾西部沿岸の長期土砂移動量の評価
井上 かおり; 田中 仁; 泉 典洋
海岸工学論文集, 49, 516, 520, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, 石巻湾西端の野蒜須崎浜は湾沿岸から運ばれた漂砂や鳴瀬川の供給土砂により明治前後から発達した. 今日, 河川上流の治山・治水が進み, また湾中央ではヘッドランド等海岸構造物が設置され, 野蒜海岸に流入する土砂移動量の変化が予想される. そこで, これまでの野蒜海岸を形成した土砂移動量を調べるため, ヘッドランドを考慮しない1998年以前の長期土砂移動量を評価した. 評価方法として, 空中写真による汀線解析と野蒜海岸の堆積土砂量の概算, 河床変動計算による鳴瀬川供給土砂量の計算, 湾西側の沿岸漂砂量の計算を行った. その結果, 河川・海岸を含め野蒜沿岸の長期土砂移動量は10<SUP>4</SUP>-10<SUP>5</SUP>m<SUP>3</SUP>/sであることが示された.

EXPERIMENTS ON THE INSTABILITY OF A RIVER MOUTH IN A POCKET BEACH
Vithana H. P
PROCEEDINGS OF HYDRAULIC ENGINEERING, 46, 773, 778, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, It is commonly observed that, in pocket beaches, river mouths are located at either end of beaches adjacent to one of the headlands. Izumi <I>et. al.</I> presented a linear stability theory to explain the instability of river mouths in pocket beaches. The theory shows that river mouths cannot stay stably in the central region of beaches but can stay only within regions near either end of beaches when the capability of longshore sediment transport is not sufficient compared with the load of river sediment supply. In this study, a series of experiments are performed to study the instability of river mouths with the use of a simplified physical model. It is found that river mouths are always unstable at the center of beaches even without the shielding effect of headlands on the wave energy; thus, the shielding effect is not essential for the instability. Contrary to the theoretical results, river mouths are unstable at the beach center even if sediment supply is not sufficiently large.

ON THE HYSTERESIS OBSERVED IN THE TRANSITION PROCESS OF DUNES
YAMAGUCHI Satomi; IZUMI Norihiro
PROCEEDINGS OF HYDRAULIC ENGINEERING, 46, 707, 712, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, On the transition process of dune formation, it is known that a hysteresis is observed that the critical Froude number at which dunes disappear when discharge increases is larger than the critical Froude number at which dunes reappear when discharge decreases. In this study, in order to explain the hysteresis observed in the dune transition, a weakly nonlinear analysis is performed with the use of the growth rate expansion method. The analysis leads a nonlinear amplitude equation, which shows that when wavenumber is 0.1-0.4, the type of bifurcation appeared in the dune transition is subcritical for &sigma;=0.8. This result implies that there is a possibility that the hysteresis is caused by the subcritical bifurcation.

Nonlinear stability analysis of the step development on erosional beds
YAMAGUCHI Satomi; IZUMI Norihiro
Journal of applied mechanics, 5, 639, 648, 公益社団法人 土木学会, 2002, [Peer-reviewed]
Japanese, Scientific journal, It has been known that a series of steps often develop on an erosional bed. In this study, a weakly nonlinear stability analsys is perfomed with the use of the two-dimensional Reynolds equations. The anlysis leads the value of the first Landau coefficient in a nonlinear amplitude equation with the use of the amplitude expansion method. The results show that when the wavenumber is larger than the chracteristic wavenumber obtained in the linear stability analysis, the perturbation keeps growing in the process of the nonlinear development_ This result corresponds to the fact that steps on erosional beds develop to form a series of waterfall-like steps or overhanging cliffs in channels. This does not mean the steps can actually grow infinitely. Fully-developed steps, which cannot be described by this formulation, can be illustrated by Parker et al's theory to have an equilibrium amplitude.

Numerical Simulation of Bar Formation in Straight Channels by the NHSED2D Model
PORNPROMMIN Adichai; TERAMOTO Atsuko; IZUMI Norihiro; KITAMURA Tadanori; TSUJIMOTO Tetsuro
Journal of applied mechanics, 5, 629, 638, 公益社団法人 土木学会, 2002, [Peer-reviewed]
English, Scientific journal, Numerical simulations are performed to investigate the characteristics of the formation of alternate and multiple bars with the use of the NHSED2D model. The results of the simulations show reasonably good agreement with the results of the theoretical analysis and the experiments. It is found that periodic boundary conditions with an insufficiently small calculation domain tend to stabilize multiple bars. It is also found that there is possibility that different initial configurations lead to different equilibrium states. The reduction of the bar mode can be well explained by the theoretical results that the difference between the dominant modes associated with the maximum growth rate and the maximum equilibrium amplitude. The irregularity appeared in the reduction process of the bar mode is suggested to be caused by the nonlinear interaction between multiple modes of bars.

転波列発生の不安定性理論
泉 典洋; Huy Phuong Nguyen
応用力学論文集, 4, 611, 618, 土木学会, 2001, [Peer-reviewed]
Japanese, Scientific journal

LINEAR STABILITY ANALYSIS OF STEP INCEPTION ON EROSIONAL BEDS
YAMAGUCHI Satomi; IZUMI Norihiro
PROCEEDINGS OF HYDRAULIC ENGINEERING, 45, 751, 756, 公益社団法人 土木学会, 2001, [Peer-reviewed]
Japanese, Scientific journal, The bed form of steep channels are often characterized by a series of steps. In this paper, in order to investigate the mechanism of the inception of steps, a linear stability analysis is performed with the use of the two-dimensional Reynolds equations and the Exner equation for bed erosion. The analysis reveals that the flat bed becomes unstable resulting in the growth of sinusoidal perturbations when the Froude number is larger than 0.6-0.9 and the wavenumber is smaller than 0.7-1.0. The characteristic wavenumber of inceptive steps are in the order of 0.1-1, corresponding to a wavelength of 6-60 times the flow depth. The comparison between the predicted wavenumbers in this analysis and the measurements in Sawai's experiments shows a reasonably good agreement. The analysis can also explain that the steps migrate upstream, which agrees with the observational results.

On the location of a river mouth in a pocket beach
IZUMI Norihiro; SHUTO Nobuo; TANAKA Hitoshi; VITHANA H.P
Journal of applied mechanics, 4, 581, 590, 公益社団法人 土木学会, 2001, [Peer-reviewed]
Japanese, Scientific journal, A commonly observed feature of pocket beaches confined by two rocky headlands is that river mouths are located at either end of beaches adjacent to one of headlands. This study presents a theoretical model of instability of river mouth locations in pocket beaches in terms of a linear stablity analysis. The theory shows that river mouths cannot exist stably around the central region of beaches and only can be located at either end of beaches when the load of river sediment supply relative to the dimensions of rivers are comparatively larger than the capability of longshore sediment transport relative to the dimensions of beaches.

Depositional characteristics and numerical calculation of river mouth sediment
R. Hondo; N. Izumi; H. Tanaka
Proceedings of Coastal Engineering, JSCE, 47, 1, 536, 540, 公益社団法人 土木学会, Oct. 2000, [Peer-reviewed]
Japanese, Scientific journal

Purely erosional cyclic and solitary steps created by flow over a cohesive bed
G Parker; N Izumi
JOURNAL OF FLUID MECHANICS, 419, 203, 238, Sep. 2000, [Peer-reviewed]
English, Scientific journal

Linear stability analysis of channel inception: downstream-driven theory
N Izumi; G Parker
JOURNAL OF FLUID MECHANICS, 419, 239, 262, Sep. 2000, [Peer-reviewed]
English, Scientific journal

FINE SAND DEPOSITION ON A FLOODPLAIN DURING A FLOOD
N. Izumi; Y. Matsuda; H. Tanaka
Proceedings of Hydraulic Engineering, JSCE, 44, 419, 424, Feb. 2000, [Peer-reviewed]
Japanese, Scientific journal

EFFECTS OF VEGETATION ON GULLY FORMATION
S. Yamaguchi; N. Izumi
Proceedings of Hydraulic Engineering, JSCE, 43, 43, 605, 610, Japan Society of Civil Engineers, Feb. 1999, [Peer-reviewed]
Japanese, Surface erosion is increasingly caused by forest clearance for cultivation and urbanization. It is commonly observed that gullies formed at the edge of plateau surfaces tremendously accelerate surface erosion. It is accordingly important to study the mechanism of gully formation and the effects of vegetation in order to reduce soil erosion. This paper presents a mathematical model as to how vegetation effects on gully formation in terms of a linear stability analysis. It is suggested that vegetation decelerates gully development by reducing gully spacing and flow intensification. It is found that a slight increase of critical shear stress due to vegetation prevents gully formation effectively.

Linear stability analysis of channel inception: Downstream-driven theory.:DOWNSTREAM-DRIVEN THEORY
IZUMI Norihiro
Doboku Gakkai Ronbunshu, 614, 65, 75, 公益社団法人 土木学会, Feb. 1999, [Peer-reviewed]
Japanese, Scientific journal, A linear stability analysis of downstream-driven channel inception is performed in this study. The analysis shows that, in the case of mild slope where flow is subcritical, perturbations grow only if the wavelength is on the order of 6-100 times as large as the critical depth devided by the friction coefficient (<i>D_c</i>/<i>C_f</i>) and that the characteristic wavelength which maximizes the growth rate of perturbation scales 10 times <i>D_c</i>/<i>C_f</i>. Evaluating the friction coefficient as on the order of 0.01, an estimate of incipient channel spacing on the order of 1000 times the Froude-critical depth is obtained. It is also found that the possibility of channel inception decreases as surface slope or the critical bed shear stress relatively increases.

Simplified theories of channel inception.
N. Izumi; S. Yamaguchi
Proceedings of Hydraulic Engineering, JSCE, 42, 1105, 1110, Feb. 1998, [Peer-reviewed]
Japanese, Scientific journal

Deltaic processes at the river mouth of the Abashiri River.
M. Date; N. Izumi; H. Tanaka
Proceedings of Hydraulic Engineering, JSCE, 42, 1129, 1134, Feb. 1998, [Peer-reviewed]
Japanese, Scientific journal

Longitudinal bed profiles of bedrock incised rivers.
S. Yamaguchi; N. Izumi
Proceedings of Hydraulic Engineering, JSCE, 41, 871, 876, Feb. 1997, [Peer-reviewed]
Japanese, Scientific journal

Equilibrium Cross-Sectional Geometry of Gravel Rivers Transporting Suspended Sediment.
Izumi Norihiro; Parker Gary
Doboku Gakkai Ronbunshu, 1997, 565, 43, 55, 公益社団法人 土木学会, 1997, [Peer-reviewed]
Japanese, Scientific journal, Gravel bed rivers transporting suspended sediment often have banks composed of fine sand (what we call &ldquo;gravel bed sand bank morphology&rdquo;). A theoretical model of the formation of &ldquo;gravel bed sand bank morphology&rdquo; is presented in this paper. The theory of equilibrium cross-section of sand-silt rivers is extended to include the case of gravel bed partially covered with fine sand. The theory shows that the location of sand deposition depends on the center depth, bed slope, sand size and sand supply. It is found that the bank regions tend to be filled with fine sand if center depth and bed slope are sufficiently large, and sand size is sufficiently small, and that the central bed region is covered with fine sand otherwise.

Equilibrium Cross-Sectional Shape of Straight Sand-Silt Rivers with Permeable Dikes.
Izumi Norihiro; Ikeda Syunsuke; Parker Gary
Doboku Gakkai Ronbunshu, 1997, 565, 31, 41, 公益社団法人 土木学会, 1997, [Peer-reviewed]
Japanese, Scientific journal, A theoretical model of the equilibrium cross-sectional shape of straight sand-silt rivers with permeable dikes is presented in this paper. The theory of self-formed sand-silt rivers is extended to include the case of channels with permeable dikes. It is found that the dike region tends to be completely filled with fine sand. It is also found, on the assumption that water discharge and river bed slope are conserved, that the equilibrium center depth is increased from 3% to 30% due to the effect of permeable dikes with common densities. With the aid of the theory of equilibrium longitudinal bed profiles, the present theory can explain the observed cross-sectional change; a 70% depth increase after the insert of permeable dikes.

掃流砂・浮遊砂の流出に伴う河口テラスの初期堆積機構
伊達 政直; 泉 典洋; 田中 仁
海岸工学論文集, 44, 591, 595, 公益社団法人 土木学会, 1997, [Peer-reviewed]
Japanese, Scientific journal

The 300-year History of Struggle with Floods-Town Reform Project for Flood Hazard Mitigation in Yoshida Riverine Community
IZUMI Norihiro
土木学会誌, 81, 12, 6, 9, 土木学会, 15 Oct. 1996, [Invited]
Japanese

水路網の形成と地形の発達
泉 典洋
ながれ : 日本流体力学会誌, 15, 4, 245, 246, 社団法人 日本流体力学会, 31 Aug. 1996, [Invited]
Japanese

Self-preserving longitudinal profile of one-dimensional delta
IZUMI Norihiro; IKEDA Syunsuke
PROCEEDINGS OF HYDRAULIC ENGINEERING, 40, 915, 920, 公益社団法人 土木学会, 1996, [Peer-reviewed]
Japanese, Scientific journal, Self-preserving profiles have been observed in experimentally produced onedimensional deltas. We analytically derive such a self-preserving profile from the St. Venant shallow water equations and the continuity equation of sediment, giving profiles of concave form. The theory predicts that the increasing height of the delta front decelerates the migration of the front and reduces the gradient of the longitudinal profile. The experimental results support these results.

ON INCIPIENT CHANNELS FORMED AT THE DOWNSTREAM END OF PLATEAUX
IZUMI Norihiro; PARKER Gary
Doboku Gakkai Ronbunshu, 521, 79, 91, 公益社団法人 土木学会, Aug. 1995, [Peer-reviewed]
Japanese, Scientific journal, At the inception of channeization, gullies are seen to be formed at the downstream end of plateaux. Those gullies migrate upstream to become channels and develop into complex systems of channel network. In this paper, a mathmatical model of gully formation is presented. Velocity and surface profiles of sheet flow over the plateau with the perturbed downstream end are calculated by solving St. Venant shallow water equations with the use of singular perturbation techniques. The calculated results show the tendency of flow concentration into indentations at the downstream end as expected. Applying the &ldquo;threshold concept&rdquo; to the results, characteristic wavelength of the order of (depth/plateau slope) is obtained, which is of the same order as that obtained from the &ldquo;upstream-driven theory&rdquo;.

On fine sand deposition in gravel channels
IZUMI Norihiro; PARKER Gary
PROCEEDINGS OF HYDRAULIC ENGINEERING, 39, 665, 670, 公益社団法人 土木学会, 1995, [Peer-reviewed]
Japanese, Scientific journal, In natural rivers, it is commonly seen that gravel beds are delineated by sandy banks. A theoretical model to explain the &ldquo;gravel bed sand bank morphology&rdquo; of straight rivers is presented in this study. The theory of stable cross-section of gravel rivers is combined with that of sand-silt rivers by introducing the concept of an available function (<I>P</I>) of fine sands on gravel beds. The theory predicts the location of sand deposit in the channel for given center depth, slope and center value of <I>P</I> (available function).

INCEPTION OF CHANNELIZATION AND DRAINAGE-BASIN FORMATION - UPSTREAM-DRIVEN THEORY
N IZUMI; G PARKER
JOURNAL OF FLUID MECHANICS, 283, 341, 363, Jan. 1995, [Peer-reviewed]
English, Scientific journal

Channel Inception and Drainage Basin Development
IZUMI Norihiro; PARKER Gary
PROCEEDINGS OF HYDRAULIC ENGINEERING, 38, 203, 208, 公益社団法人 土木学会, 1994, [Peer-reviewed]
Japanese, Scientific journal, The process of channel inception is studied theoretically. Instead of the normal flow assumption used by Smith and Britherton, St. Venant shallow water equations are adopted as a flow model to include the effect of backwater and the Reynolds stress. Velocity and depth profiles of a sheet flow on a perturbed plateau is analytically solved using a perturbation technique. It is found that the flow is gathered in troughs on the plateau and that the flow intensification is maximized when perturbation wavelength is of the order of the flow depth devided by the slope.

EFFECTS OF PILE DIKES ON FLOW RETARDATION AND SEDIMENT TRANSPORT
S IKEDA; N IZUMI; R ITO
JOURNAL OF HYDRAULIC ENGINEERING-ASCE, 117, 11, 1459, 1478, Nov. 1991, [Peer-reviewed]
English, Scientific journal

STABLE CHANNEL CROSS-SECTIONS OF STRAIGHT SAND RIVERS
S IKEDA; N IZUMI
WATER RESOURCES RESEARCH, 27, 9, 2429, 2438, Sep. 1991, [Peer-reviewed]
English, Scientific journal

直線砂床河川の安定横断河床形状
泉 典洋; 池田 駿介
土木学会論文集, 429, 429, p57, 66, 土木学会, May 1991, [Peer-reviewed]
Japanese, Scientific journal

Stable channel cross-section of straight sand-silt rivers with active sediment transport.
IZUMI Norihiro; IKEDA Syunsuke
Doboku Gakkai Ronbunshu, 1991, 429, 57, 66, 公益社団法人 土木学会, 1991, [Peer-reviewed]
Japanese, Scientific journal, Mathematical models for defining cross-section of self-formed straight sand-silt rivers are presented, in which sediments are actively transported everywhere as bed load and suspended load. A balance of lateral bed load and lateral diffusive transport of suspended sediment is imposed. to maintain a stable channel cross-section. Singular perturbation technique is employed to solve the sediment balance equation, from which a relation for stable depth is derived. A resistance formula for dune-covered bed is used to obtain stable width. It is revealed theoretically that the channel-center depth relative to sediment size is approximately proportional to S^-0.82 for natural sand-silt rivers. The analysis is found to agree reasonably well with laboratory and field data.

Transverse diffusion coefficients of suspended sediment.
IKEDA Syunsuke; IZUMI Norihiro
Doboku Gakkai Ronbunshu, 1991, 434, 47, 55, 公益社団法人 土木学会, 1991, [Peer-reviewed]
Japanese, Scientific journal, Measurements on the lateral diffusion coefficients of suspended sediment were performed in straight laboratory flumes with piles placed in stagger and side slope, respectively. Cross-sectional distributions of fluid velocity and concentration of suspended sediment were measured in detail, from which the diffusion coefficients were calculated. It was found that the lateral diffusion coefficient is about 0.24<i>u</i>*<i>D</i>, which is much larger than the value observed for turbulent flows without lateral velocity gradient. The reason is that the lateral velocity gradient induces instability of flow and generates organized vortices which effectively transport longitudinal fluid momentum and suspended sediment.

TRANSVERSE DIFFUSION RATES OF FLUID MOMENTUM AND SUSPENDED SEDIMENT NEAR SIDE BANKS
S IKEDA; N IZUMI
ENVIRONMENTAL HYDRAULICS, VOLS 1 AND 2, 403, 408, 1991, [Peer-reviewed]
English, International conference proceedings

WIDTH AND DEPTH OF SELF-FORMED STRAIGHT GRAVEL RIVERS WITH BANK VEGETATION
S IKEDA; N IZUMI
WATER RESOURCES RESEARCH, 26, 10, 2353, 2364, Oct. 1990, [Peer-reviewed]
English, Scientific journal

Stable channel cross-section of straight gravel rivers with trees on banks.
IZUMI Norihiro; IKEDA Syunsuke
Doboku Gakkai Ronbunshu, 1989, 411, 151, 160, 公益社団法人 土木学会, 1989, [Peer-reviewed]
Japanese, Scientific journal, Effect of bank vegetation on the stable channel cross-section of straight gravel rivers is studied theoretically, in which singular perturbation and matched asymptotic expansion techniques are employed to derive the lateral distributions of depth-averaged fluid velocity and the bed shear stress. A condition of sediment incipient motion is imposed at the junction of the bed and the banks to derive the stable depth, and a formula for resistance to flow is used to obtain the stable width. It is revealed that a thicker vegetation yields a larger depth and a smaller width. Increasing discharge is found to increase the effect of vegetation. The analysis is found to agree reasonably well with available field data.

Effect of Vegetation on Flow and Concentration of Suspended Sediment
IZUMI Norihiro; IKEDA Syunsuke; ITO Rikio
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 33, 313, 318, 公益社団法人 土木学会, 1989, [Peer-reviewed]
Japanese, Scientific journal, Mathmatical models for defining the lateral distributions of velocity and suspended sediment concentration in channels with vegetation are presented. Singular perturbation technique is used to define the velocity distribution, from which the sediment distribution is derived. Measurements of the velocity and the sediment concentration in a laboratory flume with vegetation models are made. These data support the model presented herein, and it is revealed that the lateral momentum and the mass diffusivity are larger than those for open channel flow without vegetation. It is found that the vertical diffusivity is not governed by the local friction velocity. The transportation of suspended sediment due to vegetation is thus quantified.

A study on the structure of evaluation of a river space in a city
Koike Tosio; Tamai Nobuyuki; Takahasi Yutaka; Izumi Norihiro; Okamura Jiro
INFRASTRUCTURE PLANNING REVIEW, 6, 105, 112, 公益社団法人 土木学会, 1988, [Peer-reviewed]
Japanese, Scientific journal, The structure of evaluation of a river space in a city is studied at the Kanda river and the Syakujii river which are typically urbanized in Tokyo. The river space is devided into the physical space and the psychological space. The influence of the geometrical characteristics of the upper- and mid- Kanda river on evaluation of the physical river space is examined. A preferable structure of river space is gained by the psychophysical approach. The cognitive model for evaluation of the psychological river space is presented. The difference of the structures of evaluation is examined at two zones in the Syakujii river using the model.

METHODS OF RIVER RESTORATION FOR BARE GRAVEL BARS AND THEIR EFFORTS IN THE SATSUNAI RIVER
天羽淳; 矢部健一郎; 渡邊康玄; 泉典洋; 大串弘哉; 山口里実; 大石哲也, 河川技術論文集(Web), 29, 299, 304, 2023, [Peer-reviewed]
Japanese

Grain size distribution of cyclic steps produced by surge turbidity currents in a flume
横川美和; 藤田和典; 森勇; FERNANDEZ Roberto; CZAPIGA Matt; BERENS John; KWANG Jeffrey; 内藤健介; PARKER Gary; 泉典洋; 成瀬元, 日本堆積学会大会プログラム・講演要旨, 2021 (CD-ROM), 2021

Report on the 2020 Kuma River Flood
泉典洋, 北海道地区自然災害科学資料センター報告, 34, 3, 21, 2021
北海道地区自然災害科学資料センター (北海道大学大学院工学研究院), Japanese

厚真川山地小流域を対象とした水・土砂流出および地形特性—Characteristics of runoff, sediment transport and topography over the sub-catchment in Aduma river basin—北海道胆振東部地震における厚真川流域の土砂災害に関する分野横断型調査研究
宮崎 功太郎; 星野 剛; 山田 朋人; 泉 典洋; 橋場 雅弘, 研究所紀要 / [北海道河川財団] [編], 31, 179, 197, Dec. 2020
北海道河川財団, Japanese

会長・理事会特別シリーズ(No.6)特別座談会(第5回)2020年7月22日(水) オンライン会議システムにて 土木の原点に想いを馳せる
家田 仁; 泉 典洋; 木村 亮; 島村 誠; 松島 学; 茶木 環, 土木学会誌, 105, 12, 2, 9, Dec. 2020
土木学会, Japanese

The 68^th JSEE Annual Conference & Exposition
IZUMI Norihiro, Journal of JSEE, 68, 6, 6_2, 6_4, 2020
Japanese Society for Engineering Education, Japanese

Urgent Symposium: Engineering Education in the Era of COVID-19－What’s Happening Now, and What’ s in Future－
IZUMI Norihiro, Journal of JSEE, 68, 6, 6_19, 6_20, 2020
Japanese Society for Engineering Education, Japanese

ダム貯水池における混濁流を用いた排砂実験
三橋日向; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 76, 76, 2020

地震に伴って発生する海底地すべりによる混濁流の発生機構
新谷有貴; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 76, 76, 2020

令和元年台風19号及び台風21号による広域災害に関する総合研究
二瓶泰雄; 仲江川敏之; 中北英一; 竹見哲也; 山田朋人; 三隅良平; 飯塚聡; 鈴木真一; 柳瀬亘; 立川康人; 田中茂信; 佐山敬洋; 田中智大; 朝位孝二; 清水義彦; 前野詩朗; 田中仁; 吉谷純一; 田中規夫; 泉典洋; 矢野真一郎; 森脇亮; 赤松良久; 内田龍彦; 重枝未玲; 岩崎理樹; 小山毅; 長谷川兼一; 西嶋一欽; 藤本郷史; 毛利栄征; 前田健一; 岡村未対; 卜部厚志; 森口周二; 蝦名裕一; 松四雄騎; 王功輝; 竹林洋史; 鈴木素之; 田島芳満; 佐々木淳; 信岡尚道; 森信人; 有川太郎; 鈴木崇之; 下園武範; 松井正宏; 小林文明; 畑山満則; 牛山素行; 佐藤健; 梶谷義雄, 自然災害科学総合シンポジウム要旨集, 57th, 9, 22, 2020
令和元年台風19号では, 東日本の非常に広い範囲で長時間の豪雨をもたらし, 大規模な洪水氾濫が発生すると共に, 台風による過去最多の士砂災害件数, 竜巻などの強風被害, 記録的な高潮・高波被害が発生し, 甚大な人的・物的被害が生じた。その約2週間後には, 日本南岸の低気圧と台風21号による大雨が発生し, 千菓県や福島県などにて洪水氾濫が発生した。本研究では, 科研費・特別研究促進費による突発災害調査研究により, 台風19号, 21号による広域災害について, 全国から多分野の研究者が集結した総合研究を実施した。本報はその成果の一部を取りまとめたものである。また, 今後に向けての提言も一覧できる形でまとめている。
2020年9月1日(火), 於 : Zoomによるオンライン開催, 京都大学防災研究所自然災害研究協議会, Japanese

Experimental study on sandbars evolution with bed erosion growth in mixed alluvial-bedrock uniformly curved channel
Mamy Rija Andriamboavonjy; Adriano Coutinho Lima; Norihiro Izumi, 22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", 2020

岩盤侵食による滝や滝群の発生機構
小峰秋房; 泉典洋; 井上卓也, 土木学会北海道支部論文報告集(CD-ROM), 76, 2020

多地点水位情報と一次元不定流解析を用いたデータ同化モデルの開発—DEVELOPMENT OF DATA ASSIMILATION MODEL USING ONE-DIMENSIONAL UNSTEADY FLOW MODEL AND WATER LEVEL DATA AT MULTIPLE-POINTS
西口 亮太; 壇 鉄也; 泉 典洋, こうえいフォーラム = Nippon Koei technical forum : 日本工営技術情報 / 日本工営株式会社技術委員会 編, 27, 15, 20, 2019
日本工営技術委員会, Japanese

脳底動脈閉塞症に対する血栓回収療法の治療成績と転帰不良因子
田島洋佑; 早坂典洋; 海老原幸一; 須田泉; 横山大騎, 脳血管内治療(Web), 4, Supplement, 2019

Grain size distribution of surge-type turbidity currents and their bedforms in flume experiments
Fujita Kazunori; Yokokawa Miwa; Mori Isamu; Yagi Shu; Yoshida Souki; Mizutani Nobuaki; Fernandez Roberto; Czapiga Matt; Berens John; Kwang Jeffrey; Naito Kensuke; Parker Gary; Izumi Norihiro; Naruse Hajime, Annual Meeting of the Geological Society of Japan, 126th, 471, 2019
The Geological Society of Japan, Japanese

河道撹乱による礫河原再生を目的とした旧流路の回復方法
川村(山口)里実; 渡邊康玄; 泉典洋; 米元光明; 住友慶三; 矢部浩規, 寒地土木技術研究, 779, 11‐17, 17, 10 Apr. 2018
土木研究所寒地土木研究所, Japanese

サージ的混濁流によって形成されるサイクリックステップの特徴
藤田和典; 森勇; 横川美和; FERNANDEZ Roberto; CZAPIGA Matt; BERENS John; KWANG Jeffrey; 内藤健介; PARKER Gary; 泉典洋; 成瀬元, 日本堆積学会大会プログラム・講演要旨, 2018, 2018

波状道路の形成理論
瀧上直斗; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 74, 2018

管水路内における気液二相流の線形安定解析
谷川徹; DE LIMA Adriano Coutinho; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 74, 2018

自由表面流におけるソフトモード不安定の弱非線形安定解析
久原愛加; DE LIMA Adriano Coutinho; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 74, 2018

混濁流によって発生する底面不安定現象
泉典洋; PEN Sytharith; PARKER Gary, 日本地球惑星科学連合大会予稿集(Web), 2018, 2018

浸透流の局所化に着目した河川堤防の基礎地盤の不安定メカニズム—Instable failure of base layer of river levee focused on localization in 3D-flow
西村 柾哉; 前田 健一; 櫛山 総平; 泉 典洋; 齊藤 啓, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 22, 6p, May 2017
日本計算工学会, Japanese

自由表面流における流れの線形安定解析
久原愛加; DE LIMA Adriano Coutinho; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 73, 2017

混濁流によって発生する底面不安定現象
萩澤さくら; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 73, 2017

一様湾曲水路における仮想岩盤河床の侵食と砂の堆積状態の変遷
小澤春貴; 田口真矢; DE LIMA Adriano Coutinho; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 73, 2017

堤防におけるパイピング現象に成立する相似則
樋上洋介; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 73, 2017

札内川を事例とする植生の流路変動への影響
渡邉健人; 久加朋子; 山口里美; 清水康行; 泉典洋; 岩崎理樹; 石田義明, 土木学会北海道支部論文報告集(CD-ROM), 73, 2017

浸透流の局所化に着目した河川堤防の基礎地盤の不安定メカニズム
西村柾哉; 前田健一; 櫛山総平; 泉典洋; 齊藤啓, 計算工学講演会論文集(CD-ROM), 22, 2017

河川堤防における漏水対策型水防工法の浸透破壊に対する効果
櫛山総平; 前田健一; 泉典洋; LI Zhaoqing; 西村柾哉; 齊藤啓, 地盤工学研究発表会発表講演集(CD-ROM), 52nd, 2017

三次元浸透流に着目した透水性基礎地盤を有する河川堤防の噴砂孔のモデル化
西村柾哉; 前田健一; LI Zhaoqing; 櫛山総平; 泉典洋; 斎藤啓, 地盤工学研究発表会発表講演集(CD-ROM), 52nd, 2017

サージの長さが混濁流起源のサイクリックステップに与える影響
藤田和典; 森勇; 横川美和; ARRIETA Roberto Fernandez; CZAPIGA Matt; BERENS John; KWANG Jeffrey; 内藤健介; PARKER Gary; 泉典洋; 成瀬元, 日本地質学会学術大会講演要旨, 124th, 2017

混濁流によって発生する底面不安定現象
泉典洋; 萩澤さくら, 日本地球惑星科学連合大会予稿集(Web), 2017, 2017

Hysteresis of Alluvial Cover in Clast-smooth Bedrock Channel
井上 卓也; 泉 典洋; 清水 康行, 寒地土木研究所月報, 753, 2, 11, Feb. 2016
土木研究所寒地土木研究所, Japanese

底面に冷熱源を持つ回転水槽実験における回転初期の遷移過程と高さ依存性
一瀬輪子; 北野慈和; 山田朋人; 渡部靖憲; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

乱流域の流水によって氷上に形成される界面波
泉典洋; 横川美和; 角田尭史; 石黒友紀, 日本堆積学会大会プログラム・講演要旨, 2016, 2016

底面摩擦を考慮した円形跳水現象の定式化
有雅正修; 山田朋人; 横川美和; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

海底混濁流が形成する界面波の線形安定解析
萩澤さくら; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

混濁流によって海底に形成される界面波の形成条件と形状特性
畠山順吉; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷界面波が形成する密度流の速度分布と温度分布測定の試み
長谷川貴士; 角田尭史; 泉典洋; 横川美和; 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷床上を流れるカタバ風の流速および温度の測定実験
角田尭史; 長谷川貴士; 泉典洋; 横川美和; 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

カタバ風の発生と発達のプロセス
和田萌実; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷上のステップ地形の発達:理論解析とアナログ実験の比較
横川美和; 泉典洋; 内藤健介; PARKER Gary; 山田朋人; GREVE Ralf, 日本堆積学会大会プログラム・講演要旨, 2016, 2016

Morphology of cyclic steps due to density flows in flume experiments
Yokokawa Miwa; Naruse Hajime; Muto Tetsuji; Izumi Norihiro, Annual Meeting of the Geological Society of Japan, 123rd, 217, 2016
The Geological Society of Japan, Japanese

気候変動への対応を視野に入れた盛土内水位予測モデルの開発
西村聡; 所哲也; 泉典洋; 山田朋人, 地盤工学研究発表会発表講演集(CD-ROM), 51st, 2016

津波によって発生する混濁流と堆積物移動についての水路実験(予報)
横川美和; 中島孝彰; 坂田祐樹; 山本大貴; 増田富士雄; 泉典洋, 日本地球惑星科学連合大会予稿集(Web), 2016, 2016

Viscous shear layers in partially vegetated channels
A. C. Lima; N. Izumi, River Flow - Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2016, 2276, 2285, 2016

ROTATING FLUID EXPERIMENT WITH BOTTOM SUBJECTED TO HEATED AND COOLED
Ichinose Rinko; Kitano Yoshikazu; Yamada Tomohito; Watanabe Yasunori; Izumi norihiro, Proceeding of Annual Conference, 28, 100131, 2015
The weather condition in the middle latitudes is controlled by westerly wind and high and low pressures, and these phenomena are interpreted as the baroclinic instability waves. A rotating fluid experiment by Fultz and Hide are known as the typical laboratory experiments of baroclinic instability waves. In this study, we introduced a new equipment having the unique feature characterized by the heated and cooled bottom. By this condition, 4-6 zonal wave numbers were observed and flow field were dynamically changed with time. At the sametime, it was observed that the vorticity on center changed with baroclinic waves with time., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

BAR INSTABILITY WITH BANK EROSION
UDDIN Md Jahir; IZUMI Norihiro; HASEGAWA Kazuyoshi, 水工学論文集 土木学会水工学委員会 編, 59, I_121, 126, 2015
土木学会, English

「バーブ」による河岸の防御と魚類の生息環境の創出
渡辺恵三; 渡辺恵三; 岩瀬晴夫; 岩瀬晴夫; 野村圭司; 野村圭司; 小森友晴; 卜部浩一; 卜部浩一; 泉典洋; 泉典洋, 応用生態工学会研究発表会講演集, 19th, 2015

底面の加熱および冷却を伴う回転流体水槽実験
一瀬輪子; 山田朋人; 北野慈和; 渡部靖憲; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

回転する水路に形成されるサイクリックステップ
有雅正修; 山田朋人; 横川美和; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

東日本大震災に起因する津波起源混濁流
和田萌実; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

海底混濁流によって形成される界面波
萩澤さくら; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

カタバ風によって流れ-氷界面に形成される界面波
角田尭史; 石黒友紀; 泉典洋; 横川美和; 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

火星北極冠における円形跳水現象
有雅正修; 山田朋人; 泉典洋; 横川美和, 地球環境シンポジウム講演集, 23rd, 197, 201, 2015
土木学会, Japanese

感潮域における水路網形成
久世晴日; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

底面に多孔質媒体を有する開水路の流れの安定性
吉村知祐; DE LIMA Adriano Coutinho; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

氷上を流れる流体による界面波の形成実験
石黒友紀; 角田尭史; 泉典洋; 横川美和; 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

Effects of deposition of bedload on the morphology of cyclic steps incised by abrasion due to bedload transportation on model bedrock
Yokokawa Miiwa; Kyogoku Akihito; Kotera Akira; Izumi Norihiro, Annual Meeting of the Geological Society of Japan, 122nd, 184, 2015
The Geological Society of Japan

サージ的混濁流により形成されるサイクリックステップの形態(予報)
横川美和; 山本真也; 樋口裕幸; 庄境大貴; CLARKE John Hughes; 泉典洋, 日本堆積学会大会プログラム・講演要旨, 2015, 2015

粗い岩盤河川と滑らかな岩盤河川における砂礫被覆の数値計算
井上卓也; 泉典洋; 清水康行; PARKER Gary, 日本地球惑星科学連合大会予稿集(Web), 2015, 2015

A case study of long-and short-term hydraulic state changes in embankment in Hokkaido
Satoshi Nishimura; Tetsuya Tokoro; Tomohito Yamada; Norihiro Izumi; Maria Fernanda Rivas, 6th Japan-China Geotechnical Symposium, SJGS 2015, 34, 39, 2015, [Peer-reviewed]
Japanese Geotechnical Society, English

P236 底面からの加熱及び冷却を伴う回転水槽実験(ポスターセッション)
北野 慈和; 一瀬 輪子; 山田 朋人; 渡部 靖憲; 泉 典洋, 大会講演予講集, 107, 107, 267, 2015
日本気象学会, Japanese

乱流‐氷界面に発達する界面波
NAITO KENSUKE; IZUMI NORIHIRO; YOKOKAWA MIWA; YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-37, Feb. 2014
Japanese

回転水槽における砂面に表面流がもたらす地形形成
ARIGA MASANOBU; YAMADA TOMOHITO; IZUMI NORIHIRO; YOKOKAWA MIWA, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-39, Feb. 2014
Japanese

重力風による氷床上でのステップ地形の形成に関する実験的研究
SUMIDA TAKASHI; NAITO KENSUKE; IZUMI NORIHIRO; YOKOKAWA MIWA; YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70号, 70, ROMBUNNO.B-38, Feb. 2014
Japanese

On the initial development of shear layers in partially vegetated channels
LIMA Adriano Coutinho de; IZUMI Norihiro, 水工学論文集 土木学会水工学委員会 編, 58, 61, 66, 2014
土木学会, English

感潮域における水路網形成
久世晴日; 泉典洋; DE LIMA Adriano Coutinho, 土木学会北海道支部論文報告集(CD-ROM), 70, 70, 2014

多孔質体内部におけるRayleigh-Taylor不安定現象
青井智祥; 泉典洋; 前田健一, 土木学会北海道支部論文報告集(CD-ROM), 70, 2014

河川堤防決壊口における横越流量の算定
徳川亜衣子; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 70, 2014

東日本大震災における津波起源混濁流の発生源
和田萌実; 泉典洋; 渡部靖憲, 土木学会北海道支部論文報告集(CD-ROM), 70, 2014

Geometry of cyclic steps generated by turbidity currents: Examples from Squamish delta in British Colombia, Canada
Yokokawa Miwa; Yamamoto Shinya; Hughes Clarke John E.; Izumi Norihiro, Annual Meeting of the Geological Society of Japan, 121st, 207, 2014
The Geological Society of Japan

表層流れに起因して発生しうる過剰間隙水圧に着目した地盤洗掘の理論的考察
伊藤嘉; 今瀬達也; 前田健一; 久泉友二; 泉典洋, 地盤工学研究発表会発表講演集(CD-ROM), 49th, 2014

岩盤上のサイクリックステップの形成過程についての実験的研究
京極晃年; 小寺彰; 横川美和; 泉典洋, 日本堆積学会大会プログラム・講演要旨, 2014, 2014

石灰質堆積物によるステップ地形形成に関する実験的研究
下西達也; 横川美和; WONSUCK Kim; 泉典洋; GARY Parker, 日本堆積学会大会プログラム・講演要旨, 2014, 2014

カナダ・ブリティッシュコロンビア州の河口デルタ上に見られるサイクリックステップの形態
山本真也; 横川美和; HUGHES CLARKE John E.; 泉典洋, 日本堆積学会大会プログラム・講演要旨, 2014, 2014

生物の働きによって形成される石灰岩ダム地形
泉典洋; PARKER Gary, 日本堆積学会大会プログラム・講演要旨, 2014, 2014

氷上に形成されるステップ地形
NAITO KENSUKE; IZUMI NORIHIRO; YOKOKAWA MIWA; YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-07, Feb. 2013
Japanese

Vorticity Instabilitties in Wave-Breaking Process: Formations of 3D Vortex Structure, Finger Jets and Sea Sprays
渡部靖憲; 泉典洋; 猿渡亜由未, 土木学会論文集 B2(海岸工学)(Web), 69, 2, 2013

FULLY DEVELOPED STAGE OF PERTURBATIONS IN PARALLEL TRANSVERSE SHEAR FLOWS
LIMA Adriano Coutinho de; IZUMI Norihiro, 水工学論文集 土木学会水工学委員会 編, 57, 1_73, 78, 2013
土木学会, English

An experimental study on cyclic steps by bedrock incision
Yokokawa Miwa; Akira Kotera; Kyogoku Akitoshi; Izumi Norihiro, Annual Meeting of the Geological Society of Japan, 120th, 177, 2013
The Geological Society of Japan

潮汐をともなう河口デルタ地形の形成機構に関する研究
泉典洋; 久世晴日; 高橋一徳, 土木学会北海道支部論文報告集(CD-ROM), 69, 69, 2013

豊平川におけるStep-pool構造の調査研究
高橋一徳; 久世晴日; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 69, 2013

河川堤防決壊口における横越流量の算定
徳川亜衣子; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 69, 2013

Dynamics of the turbidity current generated by the 2011 Tohoku-Oki earthquake and tsunami
Arai Kazuno; Naruse Hajime; Kawamura Kiichiro; Irino Tomohisa; Ikehara Ken; Saitoh Yu; Murayama Masafumi; Miura Ryo; Hino Ryota; Ito Yoshihiro; Inazu Daisuke; Yokokawa Miwa; Izumi Norihiro, Annual Meeting of the Geological Society of Japan, 120th, 042, 2013
The Geological Society of Japan

OSL measurement of 3.11 tsunami and offshore deposits
KITAZAWA Toshiyuki; ARAI Kazuno; NARUSE Hajime; ISHIMARU Takuya; YOKOKAWA Miwa; SAITOH Yu; MATSUMOTO Dan; SATO Tomoyuki; TANAKA Gengo; IZUMI Norihiro; KAMAO Katsura; KT-12-9 Shipboard scientists, Annual Meeting of the Geological Society of Japan, 120th, 406, 2013
The Geological Society of Japan

東北沖浅海域における東北地方太平洋沖地震・津波に伴うイベント堆積物
新井和乃; 成瀬元; 入野智久; 池原研; 笠谷貴史; 金松敏也; 野牧秀隆; 齋藤有; 横川美和; 泉典洋, ブルーアース要旨集, 2013, 2013

東日本大震災イベント堆積物のOSL測定
北沢俊幸; 新井和乃; 成瀬元; 石丸卓哉; 横川美和; 齋藤有; 松本弾; 佐藤智之; 田中源吾; 泉典洋; 亀尾桂, 日本堆積学会大会プログラム・講演要旨, 2013, 2013

氷上を流れる流体によるステップ地形の発達
横川美和; 泉典洋; 内藤健介, 日本堆積学会大会プログラム・講演要旨, 2013, 2013

東北沖津波による発生した混濁流のダイナミクス
新井和乃; 成瀬元; 川村喜一郎; 三浦亮; 日野亮太; 伊藤喜宏; 稲津大祐; 入野智久; 池原研; 村山雅史; 横川美和; 泉典洋, 日本堆積学会大会プログラム・講演要旨, 2013, 2013

海陸の熱的コントラストの変化に伴う石狩川流域における水循環システムの解明—Hydrological Cycles over Ishikari River Basin associated with Change of Land-Sea Thermal Contrast
山田 朋人; 福島 大輝; 宮崎 真; 泉 典洋, 研究所紀要 / [北海道河川財団] [編], 23, 139, 145, Dec. 2012
北海道河川財団, Japanese

火星北極冠におけるサイクリックステップに関する実験的研究
NAITO KENSUKE; SHIMIZU HIROKI; IZUMI NORIHIRO; YOKOKAWA MIWA; YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-56, Feb. 2012
Japanese

密度界面に発生するship waveの物理機構
KITANO YOSHIKAZU; YAMADA TOMOHITO; IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-11, Feb. 2012
Japanese

雨水流出実験装置を用いた水路形成実験
泉典洋, 京都大学防災研究所年報(CD-ROM), 55, 2012

降雨を受ける急勾配斜面上に発生する水路群
泉典洋; 長原準也; 竹林洋史; 藤田正治, 土木学会年次学術講演会講演概要集(CD-ROM), 67th, 2012

サイクリックステップとアンティデューンの特徴
横川美和; 武藤鉄司; 成瀬元; 泉典洋; PARKER Gary, 日本堆積学会大会プログラム・講演要旨, 2012, 2012

密度流によるサイクリックステップの形成条件
成瀬元; 泉典洋; 武藤鉄司; 横川美和, 日本堆積学会大会プログラム・講演要旨, 2012, 2012

降雨条件下における地表面の水路形成間隔
長原準也; 泉典洋; 藤田正治; 竹林洋史, 土木学会北海道支部論文報告集(CD-ROM), 68, 2012

河床低下を考慮に入れた蛇行の線形安定解析
青木章宜; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 68, 2012

三角州の形成に潮汐が与える影響に関する実験的研究
泉典洋; 会沢里鶴, 土木学会北海道支部論文報告集(CD-ROM), (CD-ROM), 68, 2012

破堤プロセスに関する簡易モデルの開発
徳川亜衣子; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 68, 2012

Saltation height of light-weight material with upper plane bed in open channel flow: an experimental study
横川美和; 横川美和; 高木洸希; 高木洸希; 北山忠弘; 泉典洋; 泉典洋, 大阪工業大学紀要 理工編, 57, 1, 2012

2011年東北地方太平洋沖地震によって発生した混濁流の痕跡
新井和乃; 成瀬元; 石丸卓哉; 横川美和; 齋藤有; 村山雅史; 松本弾; 佐藤智之; 田中源吾; 北沢俊幸; 日野亮太; 伊藤喜宏; 稲津大祐; 泉典洋; 三浦亮; 川村喜一郎; 野牧秀隆; 亀尾桂, 日本堆積学会大会プログラム・講演要旨, 2012, 2012

The Development range of disturbance on the atmospheric density stratification
Kitano Yoshikazu; Yamada Tomohito; Izumi Norihiro, Proceeding of Annual Conference, 25, 0, 142, 142, 2012
There are many unknown issues about line-shaped rainbands (LRBs) which is one of the meso-scale meteorological phenomena making torrential rainfall events in Japan. The LRBs caused severe floods and landslide disasters such as the Fukui heavy rainfall in 2004 and the Hokkaido heavy rainfall in 2010. For disaster prevention, it is important to reveal the formation mechanism of LRBs. In Order to know the mechanism, the authors try to examine the stability of the density stratification using the method of stationary phase. To simplify the discussion, this theory considers only the up/down motion of the disturbance in the stratified atmosphere., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

Observation and linear stability analysis of formation of rhomboid rills
Noritaka Endo; Norihiro Izumi; Takashi Murakami; Youki Ueno, River, Coastal and Estuarine Morphodynamics (RCEM) 2011, 1763, 1770, Sep. 2011
Tsinghua University Press

プレーンベッド形成時の軽量粒子の動態
高木洸希; 北山忠弘; 横川美和; 泉典洋, 日本堆積学会大会プログラム・講演要旨, 2011, 2011

三陸沖海底に広がる東北地方太平洋沖地震に伴う泥質堆積物:巨大津波は混濁流を引き起こすのか?
新井和乃; 成瀬元; 泉典洋; 横川美和; 三浦亮; 川村喜一郎; 辻健; 谷川亘; 金松敏也; 藤倉克則; 村山雅史, 日本堆積学会大会プログラム・講演要旨, 2011, 2011

境界不安定現象と地形形成
泉典洋, 日本堆積学会大会プログラム・講演要旨, 2011, 2011

湧水侵食による初期水路群の形成
竹井義博; 泉典洋; PORNPROMMIN Adichai, 土木学会北海道支部論文報告集(CD-ROM), 67, 2011

河床低下を伴う砂州の線形安定解析
高畑知明; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 67, 2011

Experiments on erosion of bedrock rivers
Hashimoto, Natsuki; Izumi, Norihiro; Komatsu, Yuusuke; Watanabe, Yasuharu; Takebayashi, Hiroshi, 土木学会北海道支部論文報告集(CD-ROM), 67, B-16-1, B-16-2, 2011
公益社団法人土木学会, Japanese

越水による堤防破堤プロセス
宮脇幸大; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 67, 2011

火星の北極冠に見られるスパイラルトラフの形成過程についての実験的研究:予報
SHIMIZU HIROKI; YOKOKAWA MIWA; NAITO KENSUKE; IZUMI NORIHIRO; YAMADA TOMOHITO; GREVE RALF; SHIRAIWA TAKAYUKI, 日本堆積学会大会プログラム・講演要旨, 2011, 63, 2011
Japanese

塩水表面の凍結に伴う鉛直対流と氷層下の形状パターン
TSUJI HIKARU; YAMADA TOMOHITO; IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-51, Feb. 2010
Japanese

地球温暖化に伴う気候変動が大気循環の波数に与える影響
HATA YOSHIHIRO; YAMADA TOMOHITO; IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-33, Feb. 2010
Japanese

Linear stability analysis of bars under degradation or aggregation
TAKAHATA Tomoaki; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2010, 180, 180, 2010
The effects of river bed aggradation and degradation on bar instability is analytically studied in terms of linear stability analysis. Weakly non-equilibrium processes are taken into account by the use of the WKBJ method. In the analysis, aggradation or degradation is assumed to be sufficiently slow compared with the bed evolution due to instability, and its non-dimensional speed is used as a small parameter. It is found that river beds become stable and sand bars tend not to be formed under degradation, and that river beds become unstable under aggradation., 日本流体力学会, Japanese

Experimental study on the subcritical bifurcation of the flat bed and antidune transition
TAKAHASHI Yuki; YAMAMURA Hiroto; YOKOKAWA Miwa; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2010, 179, 179, 2010
It is suggested by the weakly nonlinear stability analysis that the bifurcation pattern of the flat bed and antidune transition correlates to the stability of upstream-migrating antidunes. In this study, we performed a series of flume experiments to observe the behavior of upstream-migrating antidunes and obtained parameters which characterize the bifurcation patterns. As a result, the strong instability of antidunes was observed when the velocity coefficient exceeds 16, which can be correlated to the subcritical bifurcation. When the velocity coefficient is small, such as around 11, antidunes are stable, showing that it is under the condition of the supercritical bifurcation. These experimental results show that the stability of the upstream-migrating antidunes changes associated with the velocity coefficient., 日本流体力学会, Japanese

ON CHANNELS FORMED ON STEEP SLOPES
Wubneh Atinkut Mezgebu; Izumi Norihiro, 日本流体力学会年会講演論文集, 2010, 93, 93, 2010
日本流体力学会, English

Linear Stability analysis of flow in open channels partially covered with vegetation
de Lima Adriano Coutinho; Izumi Norihiro, 日本流体力学会年会講演論文集, 2010, 89, 89, 2010
日本流体力学会, English

フーリエ級数展開を用いた砂州の非線形解析
青木章宜; 泉典洋, 土木学会年次学術講演会講演概要集(CD-ROM), 65th, 2010

浮遊砂を考慮した河床デューンの発生理論
中里遥介; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 66, 2010

ガリ形成に関するる実験的研究
長原準也; WUBNEH Atinkut Mezgebu; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 66, 2010

Experiments of the effect of sediment supply on riverbed configurations
Takahata Tomoaki; Izumi Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 58th, 79, 79, 2009
Riverbed configurations are determined by many factors; water discharge, channel width, riverbed material and sediment supply. Braided streams are formed when channel width related to water depth is large and sediment supply is sufficient. However, the effect of sediment supply on riverbed configurations is not fully understood. Thus, three experiments are conducted under the same conditions in water discharge, channel width and particle size of riverbed material but varying in sediment supply.
It is found that channel width becomes narrower in the case of low than that in the case of high sediment supply. In addition, bifurcation in the case of high sediment supply can take place further upstream than the case of low sediment supply., National Committee for IUTAM, Japanese

Experiments on the gully development due to seepage erosion
Takei Yoshihiro; Izumi Norihiro; Pornprommin Adichai, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 58th, 83, 83, 2009, [Peer-reviewed]
This study aims to fulfill a lack of the fundamental knowledge in the seepage erosion mechanism.

I carried out experiments using a apparatus with wide chamber that can vary the bed gradient.I ingenerate a seepage flow and observe the appearance of seepage erosion.A series of experiments is conducted with varying sediment layer thickness,bed gradient and discharge.I analyzed how the seepage erosion affects the formation of gullies,comparing the values of gully width,shape,intervals of formation and verocity.

From experiments, as the bed gradient increase,gully width increase,channel bifurcations are more difficult to appear and velocity of gully formation decrease.I could see 2 patterns of interval of formation from differences of layer thickness:as the bed gradient increase,interval increase and as the bed gradient decrease, interval decrease.
, National Committee for IUTAM, Japanese

The experimental study of the dune formation in closed conduits
hiratsuka tomofumi; seki yohei; izumi norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 58th, 74, 74, 2009
In this study, the author investigated the limit of dune formation in closed conduits empirically as one of the studies of the river-bed evolution in closed conduits.

I used the experimental conduit (80 millimeters wide, 150 millimeters high and 2 meters long) that circulated sand with water by pump to continue the experiments for long times.

This study is based on the linear stability analysis by mixing length model by Yohei Seki, River and Watershed Engineering laboratory, and it is thought that Euler number and Shields number govern the dune formation in closed conduits in this analysis. So, I arranged experimantal data with these nondimentional numbers.

As a result, it can be assumed that the limit of dune formation is similar to the theoretical line by the analysis on the graph with Euler number and Shields number., National Committee for IUTAM, Japanese

管路内の流水と流砂の間に発生する界面不安定現象
泉典洋; 関陽平; 平塚智史, 日本混相流学会年会講演会講演論文集, 2009, 2009

掃流層モデルを用いた管路内におけるデューンの線形安定解析
関陽平; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 65, 2009

The formation of small-scale fluvial bed waves with suspended sediment transport
NAKASATO Yosuke; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2008, 234, 234, 2008
A flat bed becomes unstable, and is covered with small-scale bed waves during floods. One of the purposes of this study is to extend existing linear stability analysis taking into account only bedload to the case with active suspended sediment transport. It is found from the analysis that, with increasing suspended sediment, the critical Froude number for the bed instability is reduced, and the formation of small-scale bed waves tends to be inhibited., 日本流体力学会, Japanese

The formation of interfacial waves in horizontal pipes
SEKI Yohei; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2008, 235, 235, 2008
Interfacial waves between sediment and water in open channels, which are called dunes or antidunes, are formed in the range of small and large Froude numbers. Moreover, a phase lag between Interfacial waves and the free water surface is of importance to the instability. However, instability of the interface without free water surface has not been well understood. In this study, we perform a linear stability analysis of the interface between sediment and water in pipes with the use of the mixing length turbulent model. The analysis results show that the governing parameter is the Euler number and Shields parameter, and that the interface is unstable in the range of relatively small Euler numbers., 日本流体力学会, Japanese

Weakly nonlinear stability analysis of the dune-flat bed transition incorporating the effect of flow separation
Izumi Norihiro; Sato Hiroshige, 日本流体力学会年会講演論文集, 2008, 236, 236, 2008
A flat bed becomes unstable and is covered with lower-regime, small-scale bed forms (dunes) when the Froude number is sufficiently small during floods. It is known that either of dune and flat beds can appear in the range of relatively large Froude numbers. This can be attributed by the fact that the the dune-flat bed transition is characterized by subcritical bifurcation. In this paper, a weakly nonlinear stability analysis is performed to show the bifurcation pattern at the dune and flat bed transition is subcritical with the use of a new sediment transport formula incorporating the effect of flow separation., 日本流体力学会, Japanese

The Formation of Submarine Gullies on Continental Shelves by Turbidity Currents
YAMAGUCHI Kenji; IZUMI Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 138, 138, 2008
Patterns of parallel submarine gullies with regular transverse spacing are observed at continental margins. These gullies are thought to be formed by turbidity currents. In this study, the existing model is extended to more general cases in which the entrainment of fresh seawater cannot be neglected. A linear stability analysis is performed with the use of the layer-averaged momentum and continuity equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents., National Committee for IUTAM, Japanese

Experiments on entrainment of local sediment into suspension by turbidity currents
Niioka Masaharu; Izumi Norihiro; Yamaguchi Kenji; Sakaguchi Hide; Uzuoka Ryosuke; kido Yukari, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 139, 139, 2008
A purpose of my study is to clarify a characteristic of the local mud.
The mud for experiment was gathered from the bottom of the sea in Tokati On June 7, 2006.
The size of the flume is 15cm in height, 8cm in width and 200cm in length. The kind of flume is a rectangular sectional duct line.
The formula of the entrainment speed is expressed in Es=k(u*/ws)^n.The result became n=1, k=1.2*10^(-3). The data lower than the data of the conventional study. In addition, it may be said that concentration of salt does not affect entrainment speed., National Committee for IUTAM, Japanese

Weakly nonlinear stability analysis of dunes by the use of a sediment transport formula including the effect of the pressure gradient
Satoh Hiroshige; Izumi Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 144, 144, 2008
In order to obtain the accurate predictions of the bedform change in rivers, the accurate estimation of the sediment transport rate is important. In this study, we proposed a bedload formula, considering the effect of the pressure gradient in flow caused by the formation of dunes on the basis of Kovacs' & Parker's formula including the effect of the local bed inclination. We performed a weakly nonlinear stability analysis by the use of the sediment transport formula derived in this study. It is found that the transition between dune-covered and flat bed is charactrized by subcritical bifurcation and the results can be explained by the experimental results., National Committee for IUTAM, Japanese

釧路・十勝沖「海底地震総合観測システム」を利用した新技術の開発・応用 釧路・十勝沖のプレート収束域における海底変動現象の研究 大陸棚縁辺崖の崩壊や海底デューンの形成などの海底地形変動予測解析
松本浩幸; 川口勝義; 阪口秀; 泉典洋; 渦岡良介; 木戸ゆかり; 野田篤; 八木健太郎; 山口健治; 小寺透; 栗原梢, 海洋研究開発機構航海概要報告(CD-ROM), 2006, 2008

Formation of the fluvial dunes with active suspended sediment transport
NAKASATO Yosuke; IZUMI Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 143, 143, 2008
River dunes formed during flood increase the bed resistance, resulting in rises in water levels. Therefor, it is important to know exact conditions for the formation of dunes. One of the purpose of this study is extend the existing linear stability analysis of the formation of dunes to include active suspended sediment load. The analysis reveals that the critical Froude number is reduced and the dune formation is tend to inhibited with increasing suspended sediment load., National Committee for IUTAM, Japanese

Stability of dunes formed in pipes
SEKI Yohei; IZUMI Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 146, 146, 2008
A formation condition of dunes in rectangular ducts is obtained by linear stability analysis including mix length theory and spectral method using Chebyshev polynomials. The result was represented in contour. The unstable regions where dunes were formed appear, although dominant wavenumber does not appear. Therefore, dunes are thought to be formed and not to have specific wavelength in ducts., National Committee for IUTAM, Japanese

deposition process and dynamics of suspended solids during floods
SATO KIYO; IZUMI NORIHIRO; YOSHIKAWA YASUHIRO; YASUDA HIROYASU, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 57th, 132, 132, 2008
Recently it was understood that suspended solids was transported with nutrient salt during floods. Purpose of this study is to reveal that what influence SS concentration and consider relation between SS and sand in bed. It needs to understand behavior of SS that examine source area of SS. I classified SS in source area. I examined how to deposit of SS. Amount of silt depend on moving bed at the time of flood., National Committee for IUTAM, Japanese

矩形管路内のデューンの線形安定解析
関陽平; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 64, 2008

活発な浮遊砂を伴う河床デューンの線形安定解析
中里遥介; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 64, 2008

SS concentration at the time of the flood
Sato Kiyo; Yoshikawa Yasuhiro; Izumi Norihiro, 土木学会北海道支部論文報告集(CD-ROM), 64, 64, 2008
公益社団法人 土木学会 北海道支部, Japanese

掃流砂の非平衡性を考慮した河床デューンの弱非線形安定解析
佐藤博重; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 64, 2008

海底乱泥流による底泥の巻き上げ特性に関する実験
新岡真治; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 64, 2008

S-7 Cone Penetrometer Tests at Deep Sea Floor with Hyper-Dolphin for Earthquake Resistant Stability Analysis
Sakaguchi Hide; Uzuoka Ryosuke; Izumi Norihiro; Kido Yukari, 日本地質学会学術大会講演要旨, 114, 5, 7, 01 Sep. 2007
The Geological Society of Japan, Japanese, Summary national conference

Stability of flow on a permeable layer
OHTOMO,Hirotaka; IZUMI,Norihiro, 日本流体力学会年会講演アブストラクト集, 2007, 146, 2007
A linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law in order to investigate the instability of flow on permeable river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds., 日本流体力学会, Japanese

深海底表層地盤のコーン貫入抵抗に基づく地震時安定性の評価
渦岡良介; 泉典洋; 阪口秀; 木戸ゆかり, しんかいシンポジウム予稿集, 23rd, 2007

The Formmation of Submarine Gullies on Continental Shelves by Turbidity Currents
YAMAGUCHI,Kenji; IZUMI,Norihiro, 日本流体力学会年会講演アブストラクト集, 2007, 144, 2007
日本流体力学会, Japanese

Linear stability analysis of dunes incorporated with non-equilibrium bedload transport
Sato,Hiroshige; Izumi,Norihiro, 日本流体力学会年会講演アブストラクト集, 2007, 141, 2007
Dunes formed in lower flow regimes disappear and antidunes appear when the discharge becomes larger than a certain amount during floods. It is important to elucidate the bed instability for the prediction of flow resistance of river channels. Colombini (2004) have performed linear stability analysis of fluvial dunes by the use of the mixing length turbulent model. In this study, we performed a linear stability analysis with the use of a sediment transport formula incorporating the influence of nonequilibrium bedload movement., 日本流体力学会, Japanese

無人探査機を用いた深海地盤におけるポータブルコーン貫入試験
八木健太郎; 渦岡良介; 仙頭紀明; 早山明; 阪口秀; 木戸ゆかり; 泉典洋, 地盤工学研究発表会発表講演集, 42nd, 81, 82, 2007

Linear Stability Analysis of Channel Bifurcation
Mizushima,Hiroki; Izumi,Norihiro; Parker,Gary, 日本流体力学会年会講演アブストラクト集, 2007, 143, 2007
This study proposes a simple mathematical model of channel bifurcation, in which a channel head is modeled by an opening on a flat plane composed of erodible bed material. A linear stability analysis is performed with the use of the depth-averaged momentum equations of flow and the Exner equation of beds subject to erosion. The analysis shows that channel bifurcation tends to take place as the discharge attracted by the channel head decreases., 日本流体力学会, Japanese

越流による堤防法面侵食過程の数値シミュレーション
吉田智彦; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 63, 2007

Bagnold仮説を用いた河床デューンの線形安定解析
佐藤博重; 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 63, 2007

応用力学委員会
岸野 佑次; 泉 典洋, 土木学会誌, 91, 10, 74, 75, 15 Oct. 2006, [Invited]
Japanese

伊能大図に基づいた海岸線変化動向の評価--米代川河口周辺海岸
松冨 英夫; 田中 仁; 泉 典洋, 東北地域災害科学研究, 42, 51, 53, Mar. 2006
東北大学大学院工学研究科東北地区自然災害資料センター, Japanese

伊能図を用いた長期的河道変動解析の試み,
泉 典洋, 平成17年度土木学会東北支部技術研究発表会講演概要集, 190, 191, 2006

AM06-07-016 Weakly Nonlinear Stability Analysis of Fluival Dunes with the Mixing Length Hypothesis
Izumi,Norihiro, 日本流体力学会年会講演アブストラクト集, 2006, 196, 2006
Weakly nonlinear stability analysis of fluvial dunes is performed with the use of the growth rate expansion method incorporated with the multiple scale parturbation technique. A series of perturbation equations are solved by the use of spectral collocation method with Chebyshev polynomial. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation when C^<-1> is large, where C is the friction coefficient., 日本流体力学会, Japanese

The formation of beach cusps by waves with their crests parallel to shorelines
Norihiro Izumi; Asako Tanikawa; Hitoshi Tanaka, Proceedings of 4th International Conference on River, Coastal and Estuary Morphodynamics, 355, 363, Oct. 2005, [Peer-reviewed]
English

Analysis of historical shoreline change on Sendai Coast
Hitoshi Tanaka; Hideo Matsutomi; Norihiro Izumi, Proceedings of 3rd Asian and Pacific Coastal Engineering Conference (CD-ROM), 677, 686, Sep. 2005, [Peer-reviewed]
English

宮城県沿岸域を描いた古地図の精度に関する検討
田中 仁; 松冨 英夫; 泉 典洋, 東北地域災害科学研究, 41, 13, 18, Mar. 2005
東北大学大学院工学研究科東北地区自然災害資料センター, Japanese

海岸線変化推定への伊能大図の利用可能性--秋田県船川での経度方向の精度検討例
松冨 英夫; 田中 仁; 泉 典洋, 東北地域災害科学研究, 41, 65, 68, Mar. 2005
東北大学大学院工学研究科東北地区自然災害資料センター, Japanese

Nonlinear stability analysis of dunes by the use of sediment transport formula including the effect of the pressure
Yamaguchi Satomi; Izumi Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 54th, 301, 301, 2005
In this study, we propose a sediment transport formula taking into account the effect of the pressure gradient in flow caused by the dune formation on the basis of Kovacs & Parker's formula including the effect of the local bed inclination. We performed a nonlinear stability analysis by the use of the bedload formula derived in this study. It is found that the transition between dune-covered and flat bed is charactrized by subcritical bifurcation even if the effect of the local bed inclination is large., National Committee for IUTAM

The bifurcation process of channel heads
Izumi Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 54th, 299, 299, 2005
Channels tend to develop upslope due to the concentration of flow around their channel heads. In the developing process, a channel head sometimes splits into two or more than two branches. By repeating such a bifurcation process, simple patterns of channels evolves into complex patterns of channel networks. In this study, a mathematical model of channel bifurcation is presented in terms of secondary instability of channel heads. Linear stability analysis is performed around a channel head modeled by a hole on a flat plane. It is found that a channel head becomes unstable for perturbation and channel bifurcation is initiated when the critical depth divided by the friction coefficient decreases compared with the channel head radius., National Committee for IUTAM

The ripple-like configuration formed on erosional beds
Shimada Norikazu; Izumi Norihiro, NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 54th, 303, 303, 2005
A small wavy bed configuration is occasionally observed on erosion-dominated channel beds composed of cohesive soil such as clay. Erosion is accelerated by the avulsion of lumps of clay from the bed covered with the wavy configuration. In this study, on the basis of the idea that the wavy bed configuration is equivalent to ripples formed on beds composed of non-cohesive sediment, linear stability analysis is performed to elucidate the instability of the erosion-dominated bed. It is found that the bed becomes unstable when the wavelength of perturbations is in the range from ten to several hundred times of the thickness of a viscous sublayer., National Committee for IUTAM

THE TRANSPORT PROCESSES OF PARTICFULATE ORGANIC MATTER AND SUSPENDED SOLIDS IN FLOODS
泉典洋; PILAILAR S, 河口域生態系管理のための栄養塩輸送・管理モデルの開発 平成14-16年度 No.14205069, 2005

INCEPTIVE TOPOGRAPHY OF FLUVIAL-DOMINATED RIVER MOUTH TERRACES AND THE RIVER SEDIMENT SUPPLY
泉典洋; 田中仁; 伊達政直; 坪井宏介, 全日本広域土砂収支評価 平成14-16年度 No.14350262, 2005

Use of old maps for studying shoreline change in Japan
Hitoshi Tanaka; Hideo Matsutomi; Norihiro Izumi, Proceedings of 14th APD-IAHR Congress, 1129, 1134, Dec. 2004, [Peer-reviewed]
English

古地図に見られる名取川河口と野蒜海岸の特徴
田中 仁; 松冨 英夫; 泉 典洋, 東北地域災害科学研究, 40, 185, 190, Mar. 2004
東北大学大学院工学研究科東北地区自然災害資料センター, Japanese

A213 On the Transport of Fine Suspended Solids in Rivers
PILAILAR Sitang; IZUMI Norihiro; TANAKA Hitoshi, 日本流体力学会年会講演論文集, 2004, 234, 235, 2004
In most of the existing models of suspended sediment transport, the fine sediment is assumed to be abundant on the bed. This is not the case in most of actual rivers. Once most of fine sediment on the bed is removed from the bed, the entrainment rate is reduced due to the lack of fine sediment on the bed. This study proposes a new transport model of fine suspended solids in rivers. The model takes into account of the variation of the amount of fine particles on the bed by introducing an availability function and the continuity equation of fine particles on the bed. The model is applied to SS data obtained in a field observation during a small flood. It is found that the proposed model describes the behavior of the SS concentration considerably well compared with an existing model., 日本流体力学会, English

A231 Linear Stability Analysis of Channel Inception on Slopes with Arbitrary Shapes
PORNPROMMIN Adichai; IZUMI Norihiro; TSUJIMOTO Tetsuro, 日本流体力学会年会講演論文集, 2004, 250, 251, 2004
The existing linear stability analysis of incipient channellization was limited to the case of self-preserving slope profiles. In this study, the theory is extended to include the channellization on slopes with arbitrary shapes. Since arbitrary base state slope shape is evolving in time, the frozen time approach and the concept of momentary stability are employed. The analysis showed the possibility of channellization in the case of the arbitrary slope profile. It is found that the dominant wavelength decreases with increasing curvature of the slope., 日本流体力学会, English

A232 Formation of ripple-like morphology on purely erosional beds
SHIMADA,Norikazu; IZUMI,Norihiro, 日本流体力学会年会講演論文集, 2004, 252, 253, 2004
In the erosion process of beds composed of cohesive clay, small waves are observed to be formed on the bed surface. In this study, a liner stability analysis of the formation of ripples on noncohesive beds is applied to the formation of small waves on purely erosional beds. The analysis reveals that flat beds become unstable, resulting in the growth of sinusoidal perturbations when the wavenumber is somewhere between 0.001 and 0.07. The characteristic wavelength is of 5-10 times the reciprocal of the shear velocity. The agreement between results of the analysis as well as an experiment are found to be reasonably good., 日本流体力学会, Japanese

A215 Linear stability analysis of the formation of beach cusps
IZUMI,Norihiro; TANIKAWA,Asako; TANAKA,Hitoshi, 日本流体力学会年会講演論文集, 2004, 238, 239, 2004
Beach cusps are uniformly spaced, arcuate scallops formed at beaches. They are inseparably connected with nearshore current. The nearshore current system forms a vriety of circulation patterns, which have been attracting many researchers' interest since long time ago. While several theories have been proposed on formation nearshore current systems, Hino attributed their formation to the dynamic instability, and explained it in terms of liner stability analysis. In this study, his theory is revisited and improved in several aspects., 日本流体力学会, Japanese

The influence of physical and biological processes on the budget of fine particulate organic matter in the Nanakita River
Sitang Pilailar; Takashi Sakamaki; Hitoshi Ozaki; Norihiro Izumi; Hitoshi Tanaka, Proceedings of IWA-Asia Pacific Conference, Oct. 2003, [Peer-reviewed]
English

Effects of the Suspended Load on the Subcritical Bifurcation in The Dune-Flat Bed Transition
YAMAGUCHI Satomi; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2003, 504, 505, 2003
Stage-discharge relations of flow in streams with movable beds are known to show hysteresis between on ascending and descending stages. In this study, a weakly nonlinear stability analysis is performed in order to provide a physical explanation for the hysteresis in the transition between dune and flat bed regimes. The growth rate expansion method with the multiple scale perturbation technique is applied to the two-dimensional Reynolds-averaged, Navier-Stokes equations and a sediment continuity equation. It is found that the dune-flat bed transition is characterized by the subcritical bifurcation in the case of steep channels. The theory suggests that suspended load reduces the critical Froude number., 日本流体力学会, Japanese

Experiments of the step formation on purely erosional beds
SHIMADA Norikazu; IZUMI Norihiro, 日本流体力学会年会講演論文集, 2003, 506, 507, 2003
The purely erosional beds of steep are often characterized by a series of steps. In this paper, experiments were performed in order to study the formation and the evolution of the steps. In the experiments, the wavelength of steps were found to be of the order of six to sixty times the initial flow depth before the formation of steps. It was observed that the wavelengths reduced over time. The experimental results were compared with the theoretical results derived from a linear stability analysis. The agreement between theory and experiments were found to be good., 日本流体力学会, Japanese

The Gully Formation on Tephra Plateaus
IZUMI Norihiro; FUJII Kenji, 日本流体力学会年会講演論文集, 2003, 508, 509, 2003
This paper presents a mathematical model of the formation of gullies on slopes composed of material having relatively weak cohesivity such as freshly deposited volcanic ash. A linear stability analysis is performed with the use of the momentum equations of flow, the dispersion equation of suspended sediment, and the Exner equation extended for beds subject to erosion and deposition of suspended sediment. The analysis shows that the dominant gully spacing is of the order of 1000 times the Froude-critical depth of the sheet flow on the slope. Evaluating the Richardson-critical thickness is of the order of 0.1 m, the spacing of gullies is of the order of 100m, which is equivalent to the spacing of gulleis formed on slopes composed of cohesive material., 日本流体力学会, Japanese

七北田川中流域の砂質河床における堆積有機物量の変動
坂巻隆史; PILAILAR S; 泉典洋; 西村修, 日本水処理生物学会誌 別巻, 22, 22, 98, 2002
Japanese

Mechanism of Beach Erosion in Bangladesh and Countermeasure against Its Enhancement due to Sea Level Rise.
田中仁; 泉典洋; SAMAD M A; AZAM M H; ABDUL HYE J M, 日産科学振興財団研究報告書, 25, 53, 56, 2002
日産科学振興財団, Japanese

細粒土砂の水路形成
藤井健司; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1999, 2000

河口部土砂堆積形状の類型化とその数値計算
本堂亮; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1999, 2000

平成10年8月洪水による阿武隈川高水敷での土砂堆積現象
松田幸子; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1998, 1999

細粒堆積土砂の浮遊砂輸送による河床低下過程
藤井健司; 泉典洋; 沢本正樹, 土木学会東北支部技術研究発表会講演概要, 1998, 1999

岩木川河口部におけるデルタ堆積現象
本堂亮; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1998, 1999

粒径分布を考慮した河床変動モデルと江合川の河床低下について
北野雅幸; 泉典洋, 土木学会東北支部技術研究発表会講演概要, 1998, 1999

ガリ形成に及ぼす植生効果
山口里実; 泉典洋, 土木学会東北支部技術研究発表会講演概要, 1998, 1999

Mudflow sedimentation phenomenon to flood channel observed in Abukuma River flood, in August, 1998. (Ministry of Education S).
泉典洋; 田中仁; 松田幸子, 1998年南東北・北関東の集中豪雨災害に関する調査研究 平成10年度 No.10400011, 1999

Flood plain sedimentation in the Abukuma River Flood of August, 1998.
松田幸子; 泉典洋; 田中仁, 東北地域災害科学研究, 35(1998), 1999

Instability of river mouth locations in pocket beaches
N Izumi; N Shuto; H Tanaka, COASTAL SEDIMENTS '99, VOLS 1-3, 628, 643, 1999, [Peer-reviewed]
English

Inceptive topography of fluvial-dominated river mouth bars
N Izumi; H Tanaka; M Date, RIVER SEDIMENTATION: THEORY AND APPLICATIONS, 899, 904, 1999, [Peer-reviewed]
English

Channel reformation after the debris flow deposition in the Kumasawa River, Akita
IZUMI Norihiro, Annual report of the Society for the Promotion of Construction Engineering, 33, 33, 121, 125, 01 Apr. 1998
東北大学, Japanese

River channel reformation after debris flow in Kumazawakawa River in Akita Prefecture.
藤井健司; 泉典洋; 沢本正樹, 土木学会東北支部技術研究発表会講演概要, 1997, 1998

Sedimentation shape of the estuary where river flow is predominant.
伊達政直; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1997, 1998

Sedimentation and transportation of floating sand by river mouth jet.
坪井宏介; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1997, 1998

Water channel group formation model using a simple boundary condition.
山口里実; 泉典洋, 土木学会東北支部技術研究発表会講演概要, 1997, 1998

Vegetation community and a sandbank near Hirosegawa River Atago Long Bridge.
本堂亮; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1997, 1998

Reformation of river channel after debris flow sedimentation (field observation in Kumazawa River in Akita Prefecture).
藤井健司; 泉典洋; 沢本正樹, 土木学会年次学術講演会講演概要集 第2部, 53rd, 1998

Hydraulic effect of vegetation community on holm on flood.
本堂亮; 泉典洋; 田中仁, 土木学会年次学術講演会講演概要集 第2部, 53rd, 1998

Debris flow deposition and the subsequent degradation process in the Kumazawa River, Akita.
藤井健司; 泉典洋; 沢本正樹, 東北地域災害科学研究, 34(1997), 1998

Vertical state of mountain river. Rivers of dominant sediment transport and rivers of dominant erosion.
山口里実; 泉典洋, 土木学会東北支部技術研究発表会講演概要, 1996, 1997

Behavior of stratified muddy water which flows into reservoir.
藤井亜紀; 泉典洋, 土木学会東北支部技術研究発表会講演概要, 1996, 1997

Landform fluctuation process with runoff of bedload in river mouth.
伊達政直; 泉典洋; 田中仁, 土木学会東北支部技術研究発表会講演概要, 1996, 1997

巻頭写真
泉 典洋, 日本流体力学会誌「ながれ」, 15, 4, 245, 246, 1996
社団法人 日本流体力学会, Japanese

Gravel hydraulic function of permeable spur dike.
泉典洋; 池田駿介; PARKER G, 土木学会年次学術講演会講演概要集 第2部, 51st, 1996

地下水湧出によって形成されるガリについて
軽部裕; 泉典洋; 池田駿介, 土木学会年次学術講演会講演概要集 第2部, 50th, A, 1995

掃流砂による河口デルタの形成実験
松永考司; 泉典洋; 池田駿介, 土木学会年次学術講演会講演概要集 第2部, 50th, A, 1995

上流側から発生するチャンネルネットワ-クの初期形成機構
泉 典洋; Parker Gary, 東京工業大学土木工学科研究報告, 49, p62, 83, Jun. 1994
記事分類: 地球科学--水文学--陸水, 東京工業大学工学部土木工学科, Japanese

地下水の湧出による斜面の侵食について
軽部裕; 泉典洋, 土木学会年次学術講演会講演概要集 第2部, 49th, A, 1994

Upstream Driven Channel Inception due to Surface Erosion.
泉典洋; PARKER G, 東京工業大学土木工学科研究報告, 49, 1994

浮遊砂の横断方向拡散係数〔英文〕
池田 駿介; 泉 典洋, 東京工業大学土木工学科研究報告, 43, p43, 58, Jun. 1991
記事分類: 建設工学--河海工学--河川・運河, 東京工業大学工学部土木工学科, Japanese

Width and Depth of Self-formed Straight Gravel Rivers with Bank Vegetation
Ikeda Syunsuke; Izumi Norihiro, Research report of Department of Foundation Engineering & Department of Construction Engineering,Faculty of Engineering,Saitama University, 19, p1, 19, Dec. 1989
埼玉大学工学部建設基礎工学科・建設工学科, Japanese

Stabilized river bed profile with vegetation.
泉典洋; 池田駿介, 土木学会年次学術講演会講演概要集 第2部, 44th, 1989

Transition of river management of Kandagawa river and its utilization as urban river park.
泉典洋; 高橋裕; 小池俊雄, 土木学会年次学術講演会講演概要集 第2部, 42nd, 1987

モルフォダイナミクスの最先端
泉, 典洋; 京都大学防災研究所
京都大学防災研究所, Nov. 2015, CD-ROM1枚, Japanese

北海道大学サステナビリティ・ウィーク2011ジョイント講演会 : 持続可能な都市システムの構築を目指して
沢田, 治雄; 泉, 典洋; 目黒, 公郎; 加賀谷, 誠一
東京大学生産技術研究所都市基盤安全工学国際研究センター, Dec. 2012, 490366161X, 107p, Japanese

地すべりや斜面崩壊等の間欠的な土砂移動現象による地形形成プロセス
泉, 典洋
[北海道大学大学院工学研究科], May 2008, iv, 136p

サージ的混濁流によって形成されるサイクリックステップの特徴
藤田和典; 森勇; 横川美和; FERNANDEZ Roberto; CZAPIGA Matt; BERENS John; KWANG Jeffrey; 内藤健介; PARKER Gary; 泉典洋; 成瀬元
日本堆積学会大会プログラム・講演要旨, 25 Mar. 2018, Japanese

Features of cyclic steps formed due to surge-type turbidity currents: morphology of the steps and grain size distribution
FUJITA Kazunori; MORI Isamu; YOKOKAWA Miwa; FERNANDEZ Roberto; CZAPIGA Matt; BERENS John; KWANG Jeffrey; NAITO Kensuke; PARKER Gary; IZUMI Norihiro; NARUSE Hajime
日本地球惑星科学連合大会予稿集(Web), 2018, English

簡易動的コーン貫入試験から見る河川堤防のパイピング進展メカニズム
西村柾哉; 前田健一; 櫛山総平; 高辻理人; 泉典洋; 古溝幸永
地盤工学研究発表会発表講演集(CD-ROM), 2018, Japanese

上流からの土砂供給量の減少によって発生する海岸侵食と河床低下
開坂亮太; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

ニューラルネットワークを用いた融雪出水の流出解析
渋谷幸子; 泉典洋; 山田朋人
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

植生層の密度が開水路流に与える影響
恒川和久; DE LIMA Adriano Continho; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

円形水路における流砂の摩耗による岩盤河床の侵食
小林素直; 田口真矢; LIMA Adriano C; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

自由表面流におけるソフトモード不安定の弱非線形安定解析
久原愛加; DE LIMA Adriano Coutinho; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

管水路内における気液二相流の線形安定解析
谷川徹; DE LIMA Adriano Coutinho; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

波状道路の形成理論
瀧上直斗; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Jan. 2018, Japanese

Instable failure of base layer of river levee focused on localization in 3D-flow
西村 柾哉; 前田 健一; 櫛山 総平; 泉 典洋; 齊藤 啓
計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, May 2017, Japanese

Influence of difference in surge duration on cyclic steps due to turbidity currents
Fujita Kazunori; Izumi Norihiro; Naruse Hajime; Mori Isamu; Yokokawa Miwa; Fernandez Arrieta Roberto; Czapiga Matt; Berens John; Kwang Jeffrey; Naito Kensuke; Parker Gary
Annual Meeting of the Geological Society of Japan, 2017, Japanese
Program canceled for typhoon. However, This presentation was performed on the special session. This abstract is quotable and viewable on PDF.

Morphology of cyclic steps due to density flows in flume experiments
Yokokawa Miwa; Naruse Hajime; Muto Tetsuji; Izumi Norihiro
Annual Meeting of the Geological Society of Japan, 2016, Japanese

Viscous shear layers in partially vegetated channels
River Flow - Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2016, 01 Jan. 2016
© 2016 Taylor & Francis Group, London. Based upon the shallow water equations, linear and nonlinear stability analyses are conducted on an open channel viscous flow covered with vegetation on one side. The analyses are applied to a steady turbulent base flow which is characterized by a sub-depth scale turbulence derived from a logarithmic profile of vertical velocity. The linear stability analysis is performed for the cases of temporally growing and spatially growing disturbances. Discrepancies between results from these two approaches are found to be less relevant than those from inviscid analyses. The Landau equation is then derived on the weakly nonlinear basis. The bifurcation pattern is found to be typically supercritical, where the amplitude of the perturbations grows up to an upper bound. Experimental data from previous works support the present theory.

火星北極冠における円形跳水現象
有雅 正修; 山田 朋人; 泉 典洋
地球環境シンポジウム講演集, Sep. 2015, Japanese

P236 底面からの加熱及び冷却を伴う回転水槽実験(ポスターセッション)
北野 慈和; 一瀬 輪子; 山田 朋人; 渡部 靖憲; 泉 典洋
大会講演予講集, 2015, Japanese

Effects of deposition of bedload on the morphology of cyclic steps incised by abrasion due to bedload transportation on model bedrock
Yokokawa Miiwa; Kyogoku Akihito; Kotera Akira; Izumi Norihiro
Annual Meeting of the Geological Society of Japan, 2015

ROTATING FLUID EXPERIMENT WITH BOTTOM SUBJECTED TO HEATED AND COOLED
Ichinose Rinko; Kitano Yoshikazu; Yamada Tomohito; Watanabe Yasunori; Izumi norihiro
Proceeding of Annual Conference, 2015, Japanese
The weather condition in the middle latitudes is controlled by westerly wind and high and low pressures, and these phenomena are interpreted as the baroclinic instability waves. A rotating fluid experiment by Fultz and Hide are known as the typical laboratory experiments of baroclinic instability waves. In this study, we introduced a new equipment having the unique feature characterized by the heated and cooled bottom. By this condition, 4-6 zonal wave numbers were observed and flow field were dynamically changed with time. At the sametime, it was observed that the vorticity on center changed with baroclinic waves with time.

A case study of long-and short-term hydraulic state changes in embankment in Hokkaido
6th Japan-China Geotechnical Symposium, SJGS 2015, 01 Jan. 2015
Mechanical stability of embankments such as road embankments and river dykes is significantly influenced by their internal hydraulic states, as represented by phreatic surface location and pore water pressure distribution. The mass transfer across the embankment surfaces through water infiltration and evapotranspiration, and the internal migration of pore water to/from foundation soil layers are considered to play a major role in dictating the evolution of the hydraulic state. This paper reports a case study in which hydraulic state variations in an embankment in Hokkaido were monitored over 9 months, including a winter period with ground surface freezing and a significant snow cover. The studied embankment was relatively new, constructed with artificially mixed clay and sand which were generated by nearby excavation. The monitoring records indicate a consistent trend of under-drainage to the foundation layer all during the 9 months, with the pore water pressure at deeper parts registering minimum values during winter and reaching maxima during summer. Explanations for this and other observed features were sought by performing unsteady unsaturated seepage flow analysis with some assumed surface input models. Although the adopted models are fairly crude, the analysis results offer important insights into factors that govern the hydraulic state of low-permeability embankment in snowy cold regions.

Geometry of cyclic steps generated by turbidity currents: Examples from Squamish delta in British Colombia, Canada
Yokokawa Miwa; Yamamoto Shinya; Hughes Clarke John E; Izumi Norihiro
Annual Meeting of the Geological Society of Japan, 2014

An experimental study on cyclic steps by bedrock incision
Yokokawa Miwa; Akira Kotera; Kyogoku Akitoshi; Izumi Norihiro
Annual Meeting of the Geological Society of Japan, 2013

OSL measurement of 3.11 tsunami and offshore deposits
KITAZAWA Toshiyuki; IZUMI Norihiro; KAMAO Katsura, KT; Shipboard scientists; ARAI Kazuno; NARUSE Hajime; ISHIMARU Takuya; YOKOKAWA Miwa; SAITOH Yu; MATSUMOTO Dan; SATO Tomoyuki; TANAKA Gengo
Annual Meeting of the Geological Society of Japan, 2013

降雨条件下における地表面の水路形成間隔
長原準也; 泉典洋; 藤田正治; 竹林洋史
土木学会北海道支部論文報告集(CD-ROM), Feb. 2012, Japanese

The Development range of disturbance on the atmospheric density stratification
Kitano Yoshikazu; Yamada Tomohito; Izumi Norihiro
Proceeding of Annual Conference, 2012, Japanese
 There are many unknown issues about line-shaped rainbands (LRBs) which is one of the meso-scale meteorological phenomena making torrential rainfall events in Japan. The LRBs caused severe floods and landslide disasters such as the Fukui heavy rainfall in 2004 and the Hokkaido heavy rainfall in 2010. For disaster prevention, it is important to reveal the formation mechanism of LRBs. In Order to know the mechanism, the authors try to examine the stability of the density stratification using the method of stationary phase. To simplify the discussion, this theory considers only the up/down motion of the disturbance in the stratified atmosphere.

Cyclic steps formed in bedrock rivers
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Turbidity-current-generated cyclic steps in subaqueous environments
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Scouring of soft rock imitated with mortar by the collision of gravels
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

A Riverbed Evolution Calculation Method That Considers Variation in Riverbed Erosion of Soft Rock
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Phase diagram for antidunes and cyclic steps based on suspension index, non-dimensional Chezy resistance coefficient and Froude number
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Observation and linear stability analysis of formation of rhomboid rills
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Stability analysis of sand bars using amplitude expansion method
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Experiments on channel head bifurcation by overland flow
Proceedings of the 7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2011

Experiments on channel inception on mild slopes composed of cohesive soils
Proceedings of the 1st EIT International Conference on Water Resources Engineering, 2011

ガリ形成に関するる実験的研究
長原準也; WUBNEH Atinkut Mezgebu; 泉典洋
土木学会北海道支部論文報告集(CD-ROM), Feb. 2010, Japanese

Linear stability analysis of bars under degradation or aggregation
TAKAHATA Tomoaki; IZUMI Norihiro
日本流体力学会年会講演論文集, 2010, Japanese
The effects of river bed aggradation and degradation on bar instability is analytically studied in terms of linear stability analysis. Weakly non-equilibrium processes are taken into account by the use of the WKBJ method. In the analysis, aggradation or degradation is assumed to be sufficiently slow compared with the bed evolution due to instability, and its non-dimensional speed is used as a small parameter. It is found that river beds become stable and sand bars tend not to be formed under degradation, and that river beds become unstable under aggradation.

ON CHANNELS FORMED ON STEEP SLOPES
Wubneh Atinkut Mezgebu; Izumi Norihiro
日本流体力学会年会講演論文集, 2010, English

Linear Stability analysis of flow in open channels partially covered with vegetation
de Lima Adriano Coutinho; Izumi Norihiro
日本流体力学会年会講演論文集, 2010, English

Experimental study on the subcritical bifurcation of the flat bed and antidune transition
TAKAHASHI Yuki; YAMAMURA Hiroto; YOKOKAWA Miwa; IZUMI Norihiro
日本流体力学会年会講演論文集, 2010, Japanese
It is suggested by the weakly nonlinear stability analysis that the bifurcation pattern of the flat bed and antidune transition correlates to the stability of upstream-migrating antidunes. In this study, we performed a series of flume experiments to observe the behavior of upstream-migrating antidunes and obtained parameters which characterize the bifurcation patterns. As a result, the strong instability of antidunes was observed when the velocity coefficient exceeds 16, which can be correlated to the subcritical bifurcation. When the velocity coefficient is small, such as around 11, antidunes are stable, showing that it is under the condition of the supercritical bifurcation. These experimental results show that the stability of the upstream-migrating antidunes changes associated with the velocity coefficient.

Experiments on the gully development due to seepage erosion
Takei Yoshihiro; Izumi Norihiro; Pornprommin Adichai
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 09 Jun. 2009, Japanese
This study aims to fulfill a lack of the fundamental knowledge in the seepage erosion mechanism.
I carried out experiments using a apparatus with wide chamber that can vary the bed gradient.I ingenerate a seepage flow and observe the appearance of seepage erosion.A series of experiments is conducted with varying sediment layer thickness,bed gradient and discharge.I analyzed how the seepage erosion affects the formation of gullies,comparing the values of gully width,shape,intervals of formation and verocity.
From experiments, as the bed gradient increase,gully width increase,channel bifurcations are more difficult to appear and velocity of gully formation decrease.I could see 2 patterns of interval of formation from differences of layer thickness:as the bed gradient increase,interval increase and as the bed gradient decrease, interval decrease.

The formation of dunes in closed conduits
Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis, 2009

The formation of small-scale fluvial bedforms with active suspended sediment transport
Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis, 2009

Linear stability analysis of channelization by seepage erosion
Proceedings of the 6th IAHR Symposium on River, Coastal and Estuarine Morphodynamcis, 2009

Experiments of the effect of sediment supply on riverbed configurations
Takahata Tomoaki; Izumi Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2009, Japanese
Riverbed configurations are determined by many factors; water discharge, channel width, riverbed material and sediment supply. Braided streams are formed when channel width related to water depth is large and sediment supply is sufficient. However, the effect of sediment supply on riverbed configurations is not fully understood. Thus, three experiments are conducted under the same conditions in water discharge, channel width and particle size of riverbed material but varying in sediment supply. It is found that channel width becomes narrower in the case of low than that in the case of high sediment supply. In addition, bifurcation in the case of high sediment supply can take place further upstream than the case of low sediment supply.

The experimental study of the dune formation in closed conduits
hiratsuka tomofumi; seki yohei; izumi norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2009, Japanese
In this study, the author investigated the limit of dune formation in closed conduits empirically as one of the studies of the river-bed evolution in closed conduits.
I used the experimental conduit (80 millimeters wide, 150 millimeters high and 2 meters long) that circulated sand with water by pump to continue the experiments for long times.
This study is based on the linear stability analysis by mixing length model by Yohei Seki, River and Watershed Engineering laboratory, and it is thought that Euler number and Shields number govern the dune formation in closed conduits in this analysis. So, I arranged experimantal data with these nondimentional numbers.
As a result, it can be assumed that the limit of dune formation is similar to the theoretical line by the analysis on the graph with Euler number and Shields number.

A simple mathematical model of channel bifurcation
Mizushima H; Izumi N; Parker G
RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2, 2008

The formation of submarine gullies on continental shelves with arbitrary shapes by turbidity currents
Yamaguchi K; Izumi N
RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2, 2008

Linear stability analysis of fluvial dunes and antidunes incorporating nonequilibrium bedload transport
Sato H; Izumi N
RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2, 2008

Weakly nonlinear analysis of the dune-flat bed transition with the mixing length turbulent model
Izumi N
RIVER, COASTAL AND ESTUARINE MORPHODYNAMICS: RCEM 2007, VOLS 1 AND 2, 2008

Gully development by groundwater seepage
Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering, 2008

Experiments on the entrainment of sediment by turbidity currents with the use of submarine sediment
Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering, 2008

Linear stability analysis between river flow and seepage flow
Proceedings of Extended Abstracts and Full Papers of the 8th International Conference on Hydro-Science and Engineering, 2008

Weakly nonlinear stability analysis of the dune-flat bed transition incorporating the effect of flow separation
Izumi Norihiro; Sato Hiroshige
日本流体力学会年会講演論文集, 2008, Japanese
A flat bed becomes unstable and is covered with lower-regime, small-scale bed forms (dunes) when the Froude number is sufficiently small during floods. It is known that either of dune and flat beds can appear in the range of relatively large Froude numbers. This can be attributed by the fact that the the dune-flat bed transition is characterized by subcritical bifurcation. In this paper, a weakly nonlinear stability analysis is performed to show the bifurcation pattern at the dune and flat bed transition is subcritical with the use of a new sediment transport formula incorporating the effect of flow separation.

The formation of interfacial waves in horizontal pipes
SEKI Yohei; IZUMI Norihiro
日本流体力学会年会講演論文集, 2008, Japanese
Interfacial waves between sediment and water in open channels, which are called dunes or antidunes, are formed in the range of small and large Froude numbers. Moreover, a phase lag between Interfacial waves and the free water surface is of importance to the instability. However, instability of the interface without free water surface has not been well understood. In this study, we perform a linear stability analysis of the interface between sediment and water in pipes with the use of the mixing length turbulent model. The analysis results show that the governing parameter is the Euler number and Shields parameter, and that the interface is unstable in the range of relatively small Euler numbers.

The formation of small-scale fluvial bed waves with suspended sediment transport
NAKASATO Yosuke; IZUMI Norihiro
日本流体力学会年会講演論文集, 2008, Japanese
A flat bed becomes unstable, and is covered with small-scale bed waves during floods. One of the purposes of this study is to extend existing linear stability analysis taking into account only bedload to the case with active suspended sediment transport. It is found from the analysis that, with increasing suspended sediment, the critical Froude number for the bed instability is reduced, and the formation of small-scale bed waves tends to be inhibited.

Stability of dunes formed in pipes
SEKI Yohei; IZUMI Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
A formation condition of dunes in rectangular ducts is obtained by linear stability analysis including mix length theory and spectral method using Chebyshev polynomials. The result was represented in contour. The unstable regions where dunes were formed appear, although dominant wavenumber does not appear. Therefore, dunes are thought to be formed and not to have specific wavelength in ducts.

Weakly nonlinear stability analysis of dunes by the use of a sediment transport formula including the effect of the pressure gradient
Satoh Hiroshige; Izumi Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
In order to obtain the accurate predictions of the bedform change in rivers, the accurate estimation of the sediment transport rate is important. In this study, we proposed a bedload formula, considering the effect of the pressure gradient in flow caused by the formation of dunes on the basis of Kovacs' & Parker's formula including the effect of the local bed inclination. We performed a weakly nonlinear stability analysis by the use of the sediment transport formula derived in this study. It is found that the transition between dune-covered and flat bed is charactrized by subcritical bifurcation and the results can be explained by the experimental results.

Formation of the fluvial dunes with active suspended sediment transport
NAKASATO Yosuke; IZUMI Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
River dunes formed during flood increase the bed resistance, resulting in rises in water levels. Therefor, it is important to know exact conditions for the formation of dunes. One of the purpose of this study is extend the existing linear stability analysis of the formation of dunes to include active suspended sediment load. The analysis reveals that the critical Froude number is reduced and the dune formation is tend to inhibited with increasing suspended sediment load.

Experiments on entrainment of local sediment into suspension by turbidity currents
Niioka Masaharu; Izumi Norihiro; Yamaguchi Kenji; Sakaguchi Hide; Uzuoka Ryosuke; kido Yukari
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
A purpose of my study is to clarify a characteristic of the local mud. The mud for experiment was gathered from the bottom of the sea in Tokati On June 7, 2006. The size of the flume is 15cm in height, 8cm in width and 200cm in length. The kind of flume is a rectangular sectional duct line. The formula of the entrainment speed is expressed in Es=k(u*/ws)^n.The result became n=1, k=1.2*10^(-3). The data lower than the data of the conventional study. In addition, it may be said that concentration of salt does not affect entrainment speed.

The Formation of Submarine Gullies on Continental Shelves by Turbidity Currents
YAMAGUCHI Kenji; IZUMI Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
Patterns of parallel submarine gullies with regular transverse spacing are observed at continental margins. These gullies are thought to be formed by turbidity currents. In this study, the existing model is extended to more general cases in which the entrainment of fresh seawater cannot be neglected. A linear stability analysis is performed with the use of the layer-averaged momentum and continuity equations of turbidity currents, a dispersion equation of suspended sediment, and the Exner equation extended for the seabed subject to erosion and deposition due to turbidity currents.

deposition process and dynamics of suspended solids during floods
SATO KIYO; IZUMI NORIHIRO; YOSHIKAWA YASUHIRO; YASUDA HIROYASU
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2008, Japanese
Recently it was understood that suspended solids was transported with nutrient salt during floods. Purpose of this study is to reveal that what influence SS concentration and consider relation between SS and sand in bed. It needs to understand behavior of SS that examine source area of SS. I classified SS in source area. I examined how to deposit of SS. Amount of silt depend on moving bed at the time of flood.

S-7 Cone Penetrometer Tests at Deep Sea Floor with Hyper-Dolphin for Earthquake Resistant Stability Analysis
Sakaguchi Hide; Uzuoka Ryosuke; Izumi Norihiro; Kido Yukari
日本地質学会学術大会講演要旨, 01 Sep. 2007, Japanese

A simple mathematical model of channel bifurcation
Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2007

Linear stability analysis of fluvial dunes and antidunes incorporating nonequilibrium bedload transport
Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2007

The formation of submarine gullies on continental shelves with arbitrary shapes by turbidity currents
Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2007

Weakly nonlinear analysis of the dune-flat bed transition with the mixing length turbulent model
Proceedings of the 5th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2007

Linear stability analysis of dunes incorporated with non-equilibrium bedload transport
Sato Hiroshige; Izumi Norihiro
日本流体力学会年会講演論文集, 2007, Japanese
Dunes formed in lower flow regimes disappear and antidunes appear when the discharge becomes larger than a certain amount during floods. It is important to elucidate the bed instability for the prediction of flow resistance of river channels. Colombini (2004) have performed linear stability analysis of fluvial dunes by the use of the mixing length turbulent model. In this study, we performed a linear stability analysis with the use of a sediment transport formula incorporating the influence of nonequilibrium bedload movement.

Stability of flow on a permeable layer
OHTOMO Hirotaka; IZUMI Norihiro
日本流体力学会年会講演論文集, 2007, Japanese
A linear stability analysis is performed with the use of the Reynolds averaged Navier-Stokes equations and Darcy's law in order to investigate the instability of flow on permeable river beds. The spectral collocation method incorporated with the Chebyshev polynomials is employed in order to perform numerical solution of perturbed equations. It is found that, in the case of permeable beds, flow becomes unstable in the range of small Froude numbers where flow is stable in the case of impermeable beds.

The Formmation of Submarine Gullies on Continental Shelves by Turbidity Currents
YAMAGUCHI Kenji; IZUMI Norihiro
日本流体力学会年会講演論文集, 2007, Japanese

Linear Stability Analysis of Channel Bifurcation
Mizushima Hiroki; Izumi Norihiro; Parker Gary
日本流体力学会年会講演論文集, 2007, Japanese
This study proposes a simple mathematical model of channel bifurcation, in which a channel head is modeled by an opening on a flat plane composed of erodible bed material. A linear stability analysis is performed with the use of the depth-averaged momentum equations of flow and the Exner equation of beds subject to erosion. The analysis shows that channel bifurcation tends to take place as the discharge attracted by the channel head decreases.

Cone Penetrometer Tests at Deep Sea Floor with Hyper-Dolphin for Earthquake Resistant Stability Analysis
Sakaguchi Hide; Uzuoka Ryosuke; Izumi Norihiro; Kido Yukari
Annual Meeting of the Geological Society of Japan, 2007, Japanese

AM06-07-016 Weakly Nonlinear Stability Analysis of Fluival Dunes with the Mixing Length Hypothesis
Izumi Norihiro
日本流体力学会年会講演論文集, 2006, Japanese
Weakly nonlinear stability analysis of fluvial dunes is performed with the use of the growth rate expansion method incorporated with the multiple scale parturbation technique. A series of perturbation equations are solved by the use of spectral collocation method with Chebyshev polynomial. The analysis reveals that the dune-flat bed transition is characterized by subcritical bifurcation when C^<-1> is large, where C is the friction coefficient.

The formation of beach cusps by waves with their crests parallel to shorelines
Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2005

Inception of channelization on slopes with arbitrary shapes: erosional and depositional case
Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2005

Weakly nonlinear analysis of dunes by the use of a sediment transport formula incorporating the pressure gradient
Proceedings of 4th IAHR Symposium on River, Coastal and Estuarine Morphodynamics, 2005

Nonlinear stability analysis of dunes by the use of sediment transport formula including the effect of the pressure
Yamaguchi Satomi; Izumi Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2005
In this study, we propose a sediment transport formula taking into account the effect of the pressure gradient in flow caused by the dune formation on the basis of Kovacs & Parker's formula including the effect of the local bed inclination. We performed a nonlinear stability analysis by the use of the bedload formula derived in this study. It is found that the transition between dune-covered and flat bed is charactrized by subcritical bifurcation even if the effect of the local bed inclination is large.

The bifurcation process of channel heads
Izumi Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2005
Channels tend to develop upslope due to the concentration of flow around their channel heads. In the developing process, a channel head sometimes splits into two or more than two branches. By repeating such a bifurcation process, simple patterns of channels evolves into complex patterns of channel networks. In this study, a mathematical model of channel bifurcation is presented in terms of secondary instability of channel heads. Linear stability analysis is performed around a channel head modeled by a hole on a flat plane. It is found that a channel head becomes unstable for perturbation and channel bifurcation is initiated when the critical depth divided by the friction coefficient decreases compared with the channel head radius.

The ripple-like configuration formed on erosional beds
Shimada Norikazu; Izumi Norihiro
NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan, 2005
A small wavy bed configuration is occasionally observed on erosion-dominated channel beds composed of cohesive soil such as clay. Erosion is accelerated by the avulsion of lumps of clay from the bed covered with the wavy configuration. In this study, on the basis of the idea that the wavy bed configuration is equivalent to ripples formed on beds composed of non-cohesive sediment, linear stability analysis is performed to elucidate the instability of the erosion-dominated bed. It is found that the bed becomes unstable when the wavelength of perturbations is in the range from ten to several hundred times of the thickness of a viscous sublayer.

A231 Linear Stability Analysis of Channel Inception on Slopes with Arbitrary Shapes
PORNPROMMIN Adichai; IZUMI Norihiro; TSUJIMOTO Tetsuro
日本流体力学会年会講演論文集, 2004, English
The existing linear stability analysis of incipient channellization was limited to the case of self-preserving slope profiles. In this study, the theory is extended to include the channellization on slopes with arbitrary shapes. Since arbitrary base state slope shape is evolving in time, the frozen time approach and the concept of momentary stability are employed. The analysis showed the possibility of channellization in the case of the arbitrary slope profile. It is found that the dominant wavelength decreases with increasing curvature of the slope.

A215 Linear stability analysis of the formation of beach cusps
IZUMI Norihiro; TANIKAWA Asako; TANAKA Hitoshi
日本流体力学会年会講演論文集, 2004, Japanese
Beach cusps are uniformly spaced, arcuate scallops formed at beaches. They are inseparably connected with nearshore current. The nearshore current system forms a vriety of circulation patterns, which have been attracting many researchers' interest since long time ago. While several theories have been proposed on formation nearshore current systems, Hino attributed their formation to the dynamic instability, and explained it in terms of liner stability analysis. In this study, his theory is revisited and improved in several aspects.

A213 On the Transport of Fine Suspended Solids in Rivers
PILAILAR Sitang; IZUMI Norihiro; TANAKA Hitoshi
日本流体力学会年会講演論文集, 2004, English
In most of the existing models of suspended sediment transport, the fine sediment is assumed to be abundant on the bed. This is not the case in most of actual rivers. Once most of fine sediment on the bed is removed from the bed, the entrainment rate is reduced due to the lack of fine sediment on the bed. This study proposes a new transport model of fine suspended solids in rivers. The model takes into account of the variation of the amount of fine particles on the bed by introducing an availability function and the continuity equation of fine particles on the bed. The model is applied to SS data obtained in a field observation during a small flood. It is found that the proposed model describes the behavior of the SS concentration considerably well compared with an existing model.

A232 Formation of ripple-like morphology on purely erosional beds
SHIMADA Norikazu; IZUMI Norihiro
日本流体力学会年会講演論文集, 2004, Japanese
In the erosion process of beds composed of cohesive clay, small waves are observed to be formed on the bed surface. In this study, a liner stability analysis of the formation of ripples on noncohesive beds is applied to the formation of small waves on purely erosional beds. The analysis reveals that flat beds become unstable, resulting in the growth of sinusoidal perturbations when the wavenumber is somewhere between 0.001 and 0.07. The characteristic wavelength is of 5-10 times the reciprocal of the shear velocity. The agreement between results of the analysis as well as an experiment are found to be reasonably good.

The Gully Formation on Tephra Plateaus
IZUMI Norihiro; FUJII Kenji
日本流体力学会年会講演論文集, 2003, Japanese
This paper presents a mathematical model of the formation of gullies on slopes composed of material having relatively weak cohesivity such as freshly deposited volcanic ash. A linear stability analysis is performed with the use of the momentum equations of flow, the dispersion equation of suspended sediment, and the Exner equation extended for beds subject to erosion and deposition of suspended sediment. The analysis shows that the dominant gully spacing is of the order of 1000 times the Froude-critical depth of the sheet flow on the slope. Evaluating the Richardson-critical thickness is of the order of 0.1 m, the spacing of gullies is of the order of 100m, which is equivalent to the spacing of gulleis formed on slopes composed of cohesive material.

Experiments of the step formation on purely erosional beds
SHIMADA Norikazu; IZUMI Norihiro
日本流体力学会年会講演論文集, 2003, Japanese
The purely erosional beds of steep are often characterized by a series of steps. In this paper, experiments were performed in order to study the formation and the evolution of the steps. In the experiments, the wavelength of steps were found to be of the order of six to sixty times the initial flow depth before the formation of steps. It was observed that the wavelengths reduced over time. The experimental results were compared with the theoretical results derived from a linear stability analysis. The agreement between theory and experiments were found to be good.

Effects of the Suspended Load on the Subcritical Bifurcation in The Dune-Flat Bed Transition
YAMAGUCHI Satomi; IZUMI Norihiro
日本流体力学会年会講演論文集, 2003, Japanese
Stage-discharge relations of flow in streams with movable beds are known to show hysteresis between on ascending and descending stages. In this study, a weakly nonlinear stability analysis is performed in order to provide a physical explanation for the hysteresis in the transition between dune and flat bed regimes. The growth rate expansion method with the multiple scale perturbation technique is applied to the two-dimensional Reynolds-averaged, Navier-Stokes equations and a sediment continuity equation. It is found that the dune-flat bed transition is characterized by the subcritical bifurcation in the case of steep channels. The theory suggests that suspended load reduces the critical Froude number.

七北田川中流域の砂質河床における堆積有機物量の変動
坂巻 隆史; PILAILAR Sitang; 泉 典洋; 西村 修
日本水処理生物学会誌. 別巻 = Journal Japan Biological Society of Water and Waste, Oct. 2002, Japanese, Oral presentation

ガリ形成に及ぼす植生効果
山口里実; 泉典洋
土木学会東北支部技術研究発表会講演概要, 08 Mar. 1999, Japanese

Inceptive topography of fluvial-dominated river mouth bars.
IZUMI N; TANAKA H; DATE M
River Sediment Theor Appl, 1999, English

地下水湧出によって形成されるガリについて
軽部裕; 泉典洋; 池田駿介
土木学会年次学術講演会講演概要集 第2部, Sep. 1995, Japanese

土砂輸送特論, 2024年, 修士課程, 工学院

大学院共通授業科目（一般科目）：自然科学・応用科学, 2024年, 修士課程, 大学院共通科目

大学院共通授業科目（一般科目）：複合領域, 2024年, 修士課程, 大学院共通科目

土砂輸送特論, 2024年, 博士後期課程, 工学院

一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), 2024年, 学士課程, 全学教育

水防災工学, 2024年, 学士課程, 工学部

水圏工学, 2024年, 学士課程, 工学部

土と水の環境工学, 2024年, 学士課程, 工学部

沿岸環境工学, 2024年, 学士課程, 工学部

社会基盤と国土政策, 2024年, 学士課程, 工学部

Apr. 2019 - Present
Japanese Society for Engineering Education

2010 - Present
The Oceanographic Society of Japan

2010 - Present
日本堆積学会

2003 - Present
Japan Society of Civil Engineers

1996 - Present
The Japan Society of Fluid Mechanics

Remedial measures for river levees against piping-induced breach
Grants-in-Aid for Scientific Research
01 Apr. 2023 - 31 Mar. 2027
岡村 未対; 泉 典洋; 小野 耕平; 前田 健一; 全 邦釘
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Ehime University, 23H00198

河川堤防のパイピングメカニズム解明と維持管理法のパラダイムシフトに向けた研究
科学研究費助成事業 基盤研究(A)
01 Apr. 2019 - 31 Mar. 2023
岡村 未対; 泉 典洋; 前田 健一; 全 邦釘
2019年度の研究で，以下のことを実施し，ほぼ期待通りの成果を上げた。
■パイプ内の水の流れとそれによるパイプ孔壁の侵食とパイプ内土砂運搬の現象を解明するため，高速度カメラでパイプ内を観測し，さらに3次元浸透流解析を行った。実験は40gの遠心加速度場及び重力場で行い，粒径や模型サイズを変えた実験を組み合わせ，来年度の相似則の検討に向けたデータも蓄積した。
■堤体表面形状からパイピング部を高速自動探査する方法の開発：高水により噴砂が発生した堤防の堤体表面形状をUAVからの写真撮影とSfMで構築したDEMにより詳細に測定する。地表面変位分布からパイピングの位置，規模を推定し，現場での噴砂状況（位置，噴砂ボリューム）と比較することを近年噴砂が発生した那賀川，肱川，重信川堤防について行い，地表面の変位分布からパイピング部の推定をする方法の構築に資する成果を得た。
において実施する
■パイピング部を特定するための原位置地盤調査法の開発：実地盤におけるパイピング部やそれによる地盤のゆるみ領域の厚さは1cm～10cm程度と薄く，面的にも幅は数十cm程度と狭く，そこでの土の強度はほぼゼロである。このような箇所を直接的に検出するために，貫入装置の直径が約2cmと小さく，貫入ロッド周面摩擦の影響を排除するため，先端に高感度ロードセルを取り付け，さらにレキ当たりなどで簡単に壊れない強靭性を有する試験機を開発した。多数の貫入を行うため，バイブロ貫入機を用い２～３人作業で40箇所/日の試験法を開発し，２カ所のパイピング発生現場にて試験を実施し適用性を確認した。
日本学術振興会, 基盤研究(A), 愛媛大学, 19H00786

Sedimentary structures due to upper-flow-regime sediment-gravity-flow and a depositional model
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2018 - 31 Mar. 2023
横川 美和; 石原 与四郎; 泉 典洋; 岩崎 理樹; 中嶋 健; 成瀬 元
混濁流は地球表層で最も多くの堆積物輸送を担う現象であり，過去の混濁流によって形成された海底扇状地は石油や天然ガスの良好な貯留岩として注目されている．また，混濁流の堆積物は過去の自然災害の規模や頻度を推定する鍵になる．混濁流は内部フルード数が高くなりやすいため，高流砂階(フルード数>１)の微地形を形成しながら堆積するはずだが，それによってどのような堆積構造が地層に残されるのかはわかっていない．本研究は①高流砂階の混濁流によって形成される微地形・内部堆積構造と水理条件との関係を水路実験によって体系的に明らかにすること，②混濁流による堆積体形成の堆積モデルを構築することを目的とする．
2019年度の中断前(2019年9月28日)までの実績の概要は以下の通りである．(1)粒子径測定装置カムサイザーX2により，これまでに行った実験での高流砂階の混濁流の流れの中および堆積物の粒度分析を行った．また水路実験で混濁流によりチャネル・レビー複合体を形成し，そこに形成されるベッドフォームについて考察している．(2)混濁流によるサイクリックステップの形成についての数学モデルを作成し，検証中である．(3) 数値シミュレーションでは，開発したレイノルズ平均型の数値計算モデルを用いて大陸棚斜面を模した条件での数値計算を行った．(4) 地層の調査は主に，宮崎層群に見られるセディメントウェーブ堆積物の詳細な調査を行った．(5) 国際学会・ワークショップを通じて，研究協力者のSophie Hage氏(Southampton大学)とJoshu Mountjoy博士(ニュージーランド国立水・大気圏研究所)，さらにYanwei Zhang博士(同済大学)らと現地観測データとの比較について議論を行った．またDavid Hodgson教授(Leeds大学)とは，地層の混濁流堆積物の特徴や分布について意見交換を行った．
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Osaka Institute of Technology, 18H01293

Evaluation method for water related disaster risk considering uncertainty of rainfall patterns, rainfall-runoff and flooding
Grants-in-Aid for Scientific Research
01 Apr. 2019 - 31 Mar. 2022
Yamada Tomohito
1)Based on a large amount of rainfall data, we classified the causes of extreme rainfall into thermodynamic and dynamic aspects, and it was also found that the increase in future rainfall in mountainous areas is related to dynamic aspect in addition to thermodynamic aspect. 2)We quantified the degree of freedom of extreme rainfall in the climate system, proposed a method for predicting future changes in stochastic rainfall. 3)Based on the relationship between total rainfall and rainfall within the flood arrival time and the combined occurrence probability of the two, we showed the existence of rainfall that causes high frequency and high inundation, which could not be understood by the probability evaluation of actual total rainfall. 4)We made it possible to discuss the efficient investment ratios for river management for main and tributary rivers, considering the uncertainty of the damage reduction effect of river management caused by the spatial distribution of rainfall.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02241

The mechanisms of submarine slope failures due to earthquakes and the resulting turbidity currents
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2019 - 31 Mar. 2022
IZUMI Norihiro
We investigated the physical processes of submarine landslides triggered by earthquakes and the resulting tsunami and turbidity currents from the viewpoints of laboratory experiments, theoretical analysis, and numerical simulations.
We studied the movement of turbidity currents by solving the layer-averaged momentum equations, continuity equation, and the transport equation of suspended sediment of turbidity currents numerically. The results show that the transition from a landslide to a turbidity current that can travel long distances does not depend on the initial suspended sediment concentration or velocity unless the initial Richardson number is greater than unity.
We developed numerical simulation models to reproduce tsunamis caused by a submarine landslide and those generated by the superposition of tsunamis generated by a submarine landslide and an active fault.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02242

令和元年台風19号及び台風21号による広域災害に関する総合研究
科学研究費助成事業 特別研究促進費
04 Dec. 2019 - 31 Mar. 2021
二瓶 泰雄; 中北 英一; 竹見 哲也; 山田 朋人; 三隅 良平; 飯塚 聡; 鈴木 真一; 仲江川 敏之; 柳瀬 亘; 立川 康人; 田中 茂信; 佐山 敬洋; 田中 智大; 朝位 孝二; 前野 詩朗; 田中 仁; 吉谷 純一; 田中 規夫; 泉 典洋; 矢野 真一郎; 森脇 亮; 赤松 良久; 内田 龍彦; 重枝 未玲; 岩崎 理樹; 清水 義彦; 小山 毅; 長谷川 兼一; 西嶋 一欽; 藤本 郷史; 毛利 栄征; 前田 健一; 岡村 未対; 卜部 厚志; 森口 周二; 蝦名 裕一; 松四 雄騎; 王 功輝; 竹林 洋史; 鈴木 素之; 田島 芳満; 佐々木 淳; 信岡 尚道; 森 信人; 有川 太郎; 鈴木 崇之; 下園 武範; 松井 正宏; 小林 文明; 畑山 満則; 牛山 素行; 佐藤 健; 梶谷 義雄
令和元年台風19号及び台風21号（低気圧）による広域災害の被害状況・メカニズムの全容を明らかにすることを目的とした調査研究を進めた．ここでは，①台風・低気圧による豪雨・流出現象の気象学的解明，②広域にわたる洪水氾濫災害を引き起こしたメカニズムの解明，③多発した土砂災害・土構造物破壊におけるメカニズムの解明，④強風や高潮による被害実態の解明，⑤住民の避難行動の実態と防災情報の伝達状況の把握，の5つのテーマに焦点を絞って研究を行った．その結果，①気象レーダーなど様々な降水・気象観測データを用いて，台風・低気圧の構造や極端豪雨の発生メカニズムの一端を明らかにした．また，今次台風による降雨・流量の水文発生頻度を明らかにした．②洪水氾濫被害に対して，河川工学の見地から氾濫の発生メカニズムや被害拡大の要因の一端を調べた．洪水による建築物の被害を，防災，河川工学，構造，材料，環境の観点から分析した．③現地踏査や原位置試験，UAV調査により，斜面崩壊・土石流などの発生状況，河川堤防や道路等の土構造物の被災状況や発生メカニズムを把握した．④駿河湾，相模湾，東京湾，外房の沿岸部における台風19号に伴う高潮・高波による浸水や海岸構造物や家屋の直接的な被災状況を調べると共に，河口部における水位上昇に伴う影響評価を行った．また，同年の台風15号や2018年台風21号，24号などの過去の台風に伴う高潮・高波災害との比較を通じ，本災害の特徴を明らかにした．台風19号による強風被害の実態を調査し，今後の気象災害低減に資する情報をまとめた．⑤今次台風における大規模な人的被害の発生要因や避難者の行動，避難所での対応に関する実態を明らかにした．
日本学術振興会, 特別研究促進費, 東京理科大学, 19K24678

Mechanism of multiple hazard chains and adaptations for rapidly population decline in Japan
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
01 Apr. 2018 - 31 Mar. 2021
Osanai Nobutomo
In this study, we have organized disaster phenomena that occur in combination with large-scale earthquakes, tsunamis, volcanic eruptions, etc., including water disasters that will be exacerbated by climate change. Furthermore, the survey methods and simulation methods necessary to reduce the damage caused by them were presented. Hokkaido has an aging population and depopulation. It was also necessary to consider how disaster prevention should be in a society with a rapidly declining population in combination with maintaining the vitality of the region. In the future, Japan will not have abundant investment capacity, and complete relocation (migration) will not be easy to ensure safety against various disasters at the relocation destination. In a society with a rapidly declining population relocation destinations may be limited, so "dual life" can be a clue to avoid a crisis and maintain the vitality of the region.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 18H03819

Creation of natural-force-adaptive rivers based on the physical mechanism of long-term meandering evolution
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
01 Apr. 2015 - 31 Mar. 2020
Shimizu Yasuyuki
This study systematizes a wide range of knowledge about the long-term dynamics of meandering, and builds the basic technology for realizing river development that makes full use of natural power and individuality. In particular, focusing on the meandering that determines the plane alignment of river topography, we deeply consider the fundamental mechanism of both short-term fluctuations due to sudden disasters and long-term topographical changes from past to future, and clarified the phenomena. In addition, we analyzed the various impacts on meandering, such as vegetation, presence of estuaries and river structures, diversity of meteorological and topographical geological conditions by theoretical analysis, field surveys, and simplified physical experiments. We also have constructed a computational model that can predict the meandering development transition considering various hydraulic conditions.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 15H02267

Formation of cyclic steps due to surge-type turbidity currents: Flume experiments and applications for rock records
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2015 - 31 Mar. 2018
Yokokawa Miwa; IWASAKI Toshiki; OHISHI Yuri; OHATA Koji; HUGHES CLARKE John; PARKER Gary; TALLING Peter; CARTIGNY Matthieu
Recent field observation revealed that there are abundant “cyclic steps” (CS) formed by turbidity currents (TC) in the submarine channels and their vicinity. Here we did the first experiments on the formation of CS due to the “surge-type” TCs, and showed that the “surge-type” TCs can form CS easier compare with the continuous TC which has equivalent unit-time discharge. Experimental TCs, which is mixture of plastic particles and salt water, were released to the 7-m-long flume at Osaka Institute of Technology, with the surge durations 3, 5, 7 seconds. 130-140 surges were released into the flume for each case, and 5-6 CS were formed.
Based on these experimental results, analytical analysis and numerical simulation were performed. In addition, we applied the experimental results to rock records. We made a depositional model for the sediment waves observed in turbidites in the Miyazaki Group, Kyusyu, Japan, based on the extensive long-distance drawing of the sedimentary structures.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Osaka Institute of Technology, 15H03739

Progressive seepage failure of river levee due to piping in muti-scale mechanics
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
01 Apr. 2015 - 31 Mar. 2017
MAEDA KENICHI; IZUMI Norihiro; SAKAKIBARA Junichi; WOOD David, Muir
The relationships among the body-foundation ground properties in river levee, river water level, sand boiling dynamics, piping growth rate, and pore water pressure were investigated by model experiment and three-dimensional seepage analysis. The key parameters for occurrence and consequence conditions of piping was pointed out to be the distance between the slope toe and its dead-end, the inlet condition and the multiple layer in permeable base layer, the unevenness of inside-land, the sizes and locations of sand boiling holes where sand particles were erupted due to the velocity and pressure of the localized flow. The decrease in water velocity also was an important efficiency in traditional methods in leakage control works.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Nagoya Institute of Technology, 15K14029

Travertine steps formed by chemical and biological processes
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
01 Apr. 2013 - 31 Mar. 2015
NORIHIRO Izumi; YOKOKAWA Miwa; PARKER G.; KIM W.
Several tens of centimeters to several meters large travertine terraces, and several hundreds of meters to several kilometers large travertine dams are observed in regions covered with limestone. It is thought that the formers are formed by mainly chemical processes such as the separation of limestone due to decarbonation while the latters are caused by biological processes due to bacteria. In this study, we investigated the formation processes of the limestone step morphology through theoretical analysis, field observations, and flume experiments. We made an analysis of the formation of large scale travertine dams formed by biological processes, and clarified the formation conditions and the morphological features of travertine dams. The results of the analysis were found to be consistent with the facts observed in the field. Based on experimental results, we also proposed a mathematical model for explaining the formation of travertine terraces formed mainly by chemical processes.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 25630205

An experimental study on cyclic steps aiming for elucidation of the Mars' climate history
Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
01 Apr. 2012 - 31 Mar. 2014
YOKOKAWA Miwa; IZUMI Norihiro; HUGHES CLARKE John E.; GREVE Ralf; YAMADA Tomohito; NAITO Kensuke; SUMIDA Takashi
"Spiral troughs" (cyclic step topography) observed at the upper part of Mars' north polar ice cap is considered to be closely related to the formation history of the npc and thus the climate history of Mars. In order to explore the formation mechanism of this step topography, we operated analog experiments using ice. We also did the other experiment of cyclic steps by the gravity flows analogue to the sediment waves in the deep sea environments whose internal structures are resemble to those of spiral troughs on Mars. A theoretical model of interfacial wave formation between the fluid and ice is also created. In the analog experiments, we have succeeded in forming a interfacial waves that develop at the interface between the fluid and the ice by the flow in upper flow-regime. Behavior of these steps was consistent with that predicted by the theoretical model.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Osaka Institute of Technology, 24654165

The formation of river mouth deltas accompanied by channel networks and the preservation mechanism of tidal flats
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
01 Apr. 2011 - 31 Mar. 2014
NORIHIRO Izumi; SHIMIZU Yasuyuki; WATANABE Yasuharu
We reproduced tidal channels formed by tidal flow in an experimental flume, and performed statistic and fractal analyses to quantify geometrical features observed in the experiments. It is found from the analyses that the pattern of tidal fluctuation has a significant impact on the configuration of tidal channels. We performed numerical simulation of the formation of tidal channels with seepage flow considered. It is found that seepage flow has a strong influence on channel bifurcation, and that seepage flow increases the scale of tidal channels. It is suggested that small scale tidal channels are analogous to multiple bars formed in rivers, as channels formed on steep slopes subject to rainfall and rhomboid rills formed by waves. The large scale tidal channels are formed by sheet flow created by seepage flow coming from underground due to tidal fluctuations.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 23360209

火星北極冠に見られる螺旋状地溝の成因に関する研究
2011
Competitive research funding

水路網を伴う河口デルタの形成機構に関する研究
2011
Competitive research funding

The formation of spiral troughs on the north polar cap of Mars
2011
Competitive research funding

The formation of river mouth deltas with tidal channels
2011
Competitive research funding

Solid-liquid recursive hydraulic model for flooding river flows
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
2007 - 2010
SHIMIZU Yasuyuki; IZUMI Norihiro; WATANABE Yasunori; WATANABE Yasuharu; TAKEBAYASHI Hirofumi; YASUDA Hiroyasu
This research presents numerical and analytical models describing sediment transport occurring at wide-ranging scales in flooding river flows ; local sand-laden turbulent flow, river-bed evolution at meandering length scale, morphological effects of permeable groundwater, and responses of flood to multiple-scaled watersheds.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 19206052

河床地形動力学のための水深平均流体モデルの構築
科学研究費助成事業 特別研究員奨励費
2007 - 2009
泉 典洋; PORNPROMMN Adichai; PORNPROMMIN Adichai
今年度は,主として浸透流によるガリの形成に関する実験と,新しい掃流砂量式を用いた砂州の線形・弱非線形安定解析を行った.
浸透流によるガリ群の形成実験では,これまでプラスチック粒子を用いていたが,実際の砂を用いた実験を行った.プラスチック粒子の場合,浸透流量が大きく,ガリの発生・発達が急速に進むのに対して,実際の砂を用いた実験では発達速度が遅く,ガリ頭部の分岐が頻繁に生じることが明らかとなった.
河川の掃流砂量を見積もる際に良く用いられるのは,掃流層下面で限界掃流力に達しているというバグノルドの仮説である.横断方向に勾配を有する河床上ではこの仮説が成り立たないことが近年指摘されている.バグノルドの仮説を用いると横断方向の過小勾配の影響が過大に評価されるため実際の土砂輸送量と一致しなくなる.横断方向に局所勾配を有する河床上の横断方向掃流砂量が重要となる砂州の安定解析では,これは致命的なエラーを与える可能性がある.そこで,新たに提案された横断方向に河床勾配を有する場合の横断方向掃流砂量式と水深平均流体モデルを用いて,砂州の線形および非線形安定解析を行った.新たに提案された掃流砂量式はベクトル形式で書かれており,解析に用いるには扱い難いという欠点がある.そこで内挿式を作り,更に微小勾配の周りにテーラー展開することによって解析に使いやすい掃流砂量式を導いた.解析の結果,これまで余り精度良く予測できなかった砂州の波長や位相速度の予測精度を向上させることが可能となった.
日本学術振興会, 特別研究員奨励費, 北海道大学, 07F07116

塩水表面の凍結に伴い発生する対流と氷のパターン形成
2009
Competitive research funding

Study on optimum aquaculture production in Songkhla Lake considering tidal inlet morphology and water quality change
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
2005 - 2007
TANAKA Hitoshi; YAMAJI Hiroto; TAKASAKI Mitsuru
Songkhla Lake, located in the southern part of Thailand, connects to the Gulf of Thailand through a narrow channel, and is consists of three lakes: Thale Noi, Thale Luang and Thale Sap Songkhla. In the southernmost lake, Thale Sap Songkhla, aquaculture of seabass is now an important industry in this area. In the recent years, however, sudden death of fishes occurs frequently due to over-production in the lake. In the present study, filed investigation and numerical simulation are carried out to clarify the mechanism of water quality change in Songkhla Lake. In the field observation, automated water quality measuring devices are installed in an aquaculture area to obtain time-variation of current velocity, DO (dissolved oxygen), salinity and temperature in October 22005, 2006 and 2007. Furthermore, numerical simulation is applied to evaluate flow field in the lake. For this purpose, a depth averaged hydrodynamic model in a curvi-linear boundary fitted coordinate system is applied to achieve sufficiently high accuracy for a complicated. Topography in the lake. It is concluded that increase in DO concentration is mainly due to tidal current coming into the lake, while the reduction DO is attributed to respiration of fishes. In addition, simulation of DO concentration was conducted by using an ANN model. It can be recognized that the model results are in a good agreement with the measurement data, which indicates that the model is able to predict the DO concentration in the Songkhla Lake with a reasonable accuracy.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Tohoku University, 17254002

Geomorphological processes due to intermittent sediment movements such as land slides and slope failures
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
2005 - 2007
IZUMI Norihiro; UZUOKA Ryosuke; KAZAMA So
A mathematical model is proposed to describe the channelization on slopes composed of weakly cohesive fine sediment. The analysis is extended to include the case of slopes with arbitrary shapes. The spacing of incipient channels is found to be on the order of 1000 times the Froude critical depth of surface sheet flow. A mathematical model of channel bifurcation is also proposed. The analysis reveals that channel heads become unstable and channel bifurcation takes place when the discharge decreases. The results are found to be consistent with observations. The formation of channels due to seepage erosion is studied experimentally. It is found that governing parameters are discharge, slope and seepage layer thickness and that the spacing increases with those parameters.
A liquefaction analysis for capillary zone above ground water level is developed based on porous media theory with three phases. Simplified governing equations are derived with the assumption that the relative acceleration of pore fluid with respect to soil skeleton is small. The proposed method can reproduce the tri-axial test results well when the degree of saturation is larger than about 70%. The numerical results show that liquefaction occurred in the capillary zone when the initial saturation degree is about 60% and over.
Hydraulic gradient was analyzed by infiltration analysis with consideration of snowmelt. The probability and the road damage in the Tohoku region are shown in maps with 1 km resolutions. These maps show spatial-temporal risk distributions of sediment hazard due to some snowmelt conditions. We also focus on the influence of dam reservoirs to cause excessive sediment disasters due to anomalous weather conditions by global warming. Results of this study conform that the sediment hazard probability model performs well to predict macro scale sediment storage in dam reservoirs.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), 17360229

Mechanism of progressive failure in river dike during infiltration and overflow and its prediction
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
2005 - 2007
UZUOKA Ryosuke; SENTO Noriaki; IZUMI Norihiro
The purpose of this study is to clarify the mechanism of progressive failure of river dike during the infiltration and overflow of river water. First, infiltration-shear tests during of unsaturated soil from actual river dike were performed in order to propose a constitutive model which can reproduce shear deformation during infiltration. As the results of the infiltration-shear tests, large shear strain was produced during infiltration under initial shear condition. An elasto-plastic constitutive model was newly proposed to reproduce the results of the infiltration-shear tests. The proposed constitutive model is based on super/sub loading surface Cam-Clay model and it has a modified evolution law which is a function of suction as an internal variable. The proposed model reproduced the increase in large shear strain during infiltration in the simulation of the infiltration-shear tests. Second, dynamic soil-water-air coupled analysis method at finite strain was developed. Static self-weight analyses, quasi-static consolidation analyses, dynamic consolidation analyses and quasi-static leaking flow analyses of unsaturated soil were performed in order to verify the developed numerical code. Preliminary analyses with elastic constitutive model showed that the proposed "aerial element" which has water retention characteristics of air and small stiffness could be used for direct modeling of river water. Although further investigations into convection term are needed, aerial element can be useful for the interaction analysis between overflow water and soil embankment. Third, progressive failure of river dike during infiltration of river water was simulated with the proposed constitutive model and numerical code. Although further investigations into implicit integration of stress are needed, the numerical results showed that seepage flow appeared at the landside toe of the dike and the slope became unstable at the waterside toe of the dike when the river level rose.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Tohoku University, 17560441

乱泥流の発生と海底地形形成のメカニズム
科学研究費助成事業 萌芽研究
2005 - 2007
泉 典洋; 渦岡 良介; 阪口 秀; 木戸 ゆかり
海底で実際に採取された底泥を用いて,流れによる巻き上げ実験を行った.採取地点は十勝沖の深さ800mの海底峡谷の谷底部にあたることから,採取した底泥は乱泥流によって堆積した土砂であると考えられる.底泥の粒径分析を行った結果,中央粒径が0.013mmの均一性の低いシルトであることが明らかとなった.採取できた底泥の量がわずかであったため,限られた量の底泥でも巻き上げ実験ができるような循環型の管路実験装置を開発した.この実験装置を用いて流れによって巻き上げられる底泥の濃度を測定し,巻き上げ量式を提案した.その結果,無次元巻き上げ量は無次元摩擦速度のほぼ一乗で増加することが明らかとなった.この結果は,これまでの底泥の巻き上げ量式とほぼ同じ傾向となっている.また塩水を用いて同様の実験を行った結果,流速の遅い状況下では凝集効果によってフロックが形成され沈降量は増加するが,流速が早くなるとフロックが破壊され,凝集の効果はほとんどないことが明らかとなった.
"frozen time approach"を用いた線形安定解析の改良を行い,乱泥流による海底峡谷の初期形成機構を詳細に調べた.その結果,不安定が発生して大陸棚下流端にガリ群が形成されるのは,大陸斜面上の乱泥流が擬似的な等流状態にあるときであることが明らかとなった.その際,形成されるガリの間隔はリチャードソン限界層厚の数百倍から数千倍となることが示された.
昨年度実施した海底地盤表層のコーン貫入試験結果を基に地震時の斜面安定性を検討した.一定の勾配を有する無限長斜面を仮定し,簡易的な震度法によるすべり安全率で斜面安定性を評価する.地盤の非排水せん断強度は既往の経験式よりコーン貫入値から推定した.その結果,斜面が不安定となる水平震度の最小値は2400Galであり,今回の調査地点における海底面の地震時安定性は比較的高いことがわかった.
日本学術振興会, 萌芽研究, 17656156

中規模河床波の形成機構に関する研究
2007
Competitive research funding

Application of nonlinear dynamics to hydro-geomorphology
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
2004 - 2006
SHIMIZU Yasuyuki; IZUMI Norihiro; WATANABE Yasunori; WATANABE Yasuharu; TAKEBAYASHI Hiroshi
A weakly nonlinear analysis considering the interference between alternate bar and double-row bar has been developed. Findings show that when the two modes are on the same order, the mode cross interference controls development process of each wave and they cannot grow simultaneously. The development process of bars is strongly influenced of the mode cross interference. Hydraulic experiments and the weakly nonlinear analysis, by setting several hydraulic conditions under which either alternate bars or double-row bars formed, have been conducted to clarify a changing process of bar shape formed during flood at usual time. It is found that the channel shape at usual time is strongly affected by the bar shape during flood.
Effect of unsteady characteristics of flow and vegetation growth on number of braided streams and temporal stability of streams has been studied. The results show that the number of streams decreases and temporal change of streams is suppressed with vegetation under unsteady flow conditions. Furthermore, dynamic characteristics of bars on bed with non-uniform sediment have been studied. The results show that bar geometry on bed with non-uniform sediment has been changed with time and does not approach equilibrium state.
A new model was proposed taking proper account of the functional relation between the Froude number and the Shields number by revisiting the existing weakly nonlinear stability analysis of the transition of dune and flat bed regimes. It is found that, from the analysis, the dune-flat bed transition is characterized by subcritical bifurcation in the range of relatively small average bed slopes, and large velocity coefficient. In addition, Izumi extended the existing model of the inception of channels to the more general cases in which the base state slope profile is arbitrary given. The analysis shows that the spacing of channels is approximately one thousand times the depth of surface flow on slopes.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), HOKKAIDO UNIVERSITY, 16360242

雨季乾季のある大陸大河川の河岸侵食・土砂移動機構の解明
科学研究費助成事業 萌芽研究
2003 - 2005
風間 基樹; 渦岡 良介; 仙頭 紀明; 泉 典洋; 風間 聡
乾季と雨季で水位が大きく変動するモンスーン域の大陸河川の河岸侵食は水位が高水位から低水位に大きく落ち込む時期に,河岸が崩落することが知られている.本研究は、この現象のメカニズム解明のため,水位変動に応じて土の有効応力状態がどのように変化し,それが結果として河岸侵食にどのように影響しているのかを明らかにすることを目的としている.
平成16-17年の2年間,ラオスのビエンチャンにおけるメコン河河岸の地盤の水分状態,降雨量,河川水位を計測した結果を整理し,雨季乾季を通じての季節変動データから,河岸地盤の水分量と河川水位,降雨の関係を明らかにした。この結果,乾季初期の河川水位低下と背後地盤の水分変化にはタイムラグがあり,背後地盤から河岸方向への浸透流が発生する可能性が明らかとなった.
前年度に,現地河岸におけるボーリング調査時に採取した土砂を分析し,ラオスのビエンチャンの河岸地盤が比較的細粒のシルト層の上に,砂あるいは砂礫層が5mほど堆積している構造を持つこととそれら各層の力学特性を求めた。
現地地盤の強度特性・透水特性を再現した遠心模型実験を新たに3ケース実施した.前年度と同様に,実験は水位が高い状態から,急激に水位を低下させる過程での水圧変化や斜面の安定性を検討したものであるが,地盤の粒度や河川水位の低下パターンを変化させた実験を行った。その結果,河岸地盤の崩壊メカニズムには,陸側に残留した間隙水圧によってパイピングが生じて進行的に破壊するメカニズムと,急激な水位低下によってすべり外力が増加し地盤のせん断強度が限界に達して滑り破壊を生じるメカニズムの二つがあることがわかった。
これらの成果は,国内および国際会議に発表あるいは発表予定である。
日本学術振興会, 萌芽研究, 東北大学, 15656114

古地図に描かれた河川・海岸地形の精度評価とその活用法に関する研究
科学研究費助成事業 萌芽研究
2003 - 2005
田中 仁; 泉 典洋; 松冨 英夫
海岸地形や河川地形の変遷に関する検討を行うためには,これまで国土地理院や各種行政機関により発行された各種地形図や空中写真などが用いられてきた.しかし,これらによりさかのぼることの出来る時間スケールは数10年オーダー,長くても100年程度のものであった.そこで,本研究においては,伊能図に代表される古地図が有する地形情報に関する検討を実施した.伊能図に関してはこれまで人文地理の視点から注目を集めることが多かったが,海岸地形・河川地形の研究分野においても,200年以上も前の地形情報を与えるものとして貴重な存在であると期待される.
まず,仙台海岸,石巻海岸および秋田海岸周辺の伊能図の解析行い,その地形情報の精度に関する検討を実施した.特に,阿武隈川や北上川といった比較的大規模な河川が流入している仙台海岸,石巻海岸を対象とした検討においては,国土地理院発行の地形図と併せることにより,平均的汀線前進速度を見積もることが出来た.土砂堆積速度に関しても,75,000m^3/年との数値を得ることが出来た.また,秋田海岸を対象とする解析においても,現在の汀線位置に比べて有意な差が認められた.さらに,熊本県・球磨川を対象に,伊能図と現在の地形図を比較することによって長期的な河道変動解析を試みた.その結果,河口周辺の地形変化は良好な精度で推定できることが示された.穿入蛇行区間では伊能図の河道位置はかなりの精度を持つものの,河道はほとんど変化していないことが判った.一方,河道変動が予想される盆地内部では正確な河道位置が判らず,定量的な河道変動の推定が困難であることがわかった.しかし伊能図は定性的には多くの情報を含んでおり,使い方を吟味さえすれば有用な情報源となり得ることが判明した.これにより,200年程度の古い地形情報を解析することの有効性が示された.
日本学術振興会, 萌芽研究, 東北大学, 15656119

Development of nutrient circulation model for ecological system control in estuary
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
2002 - 2004
SAWAMOTO Masaki; OMURA Tatsuo; MANO Akira; NISIMURA Osamu; IZUMI Norihiro; KAZAMA So
Title Development of nutrient circulation model for ecological system control in estuary
In order to develop nutrient circulation model in estuary, the behavior of nutrient is investigated in river basin, river beds, rivermouth and estuary. The main results are as follows
1.The mechanism of nutrient origin in river basin was surveied and a numerical model was developed in the Natori River basin, The difference between ordinal flow condition and floods was clearly observed. The nutrient load was evaluated in various mode of transport.
2.The feature of nutrient transport in river was measured and modeled. Nutrient exchange between flow and river bed was anlysed and inportance of river bed was confirmed in circulation process.
3.Behavior of saline wedge was observed at the Abukuma rivermouth. The mixing processes of water and nutrient were analyzed. The spread of nutrient in the sea was also studied.
4.The equilibrium model for humic-iron complex in estuarine condition was developed on the basis of Dubye-Huckel theory taking account of the electrostatic interaction between iron and humic substance. The dissociation of humic-iron complex with increasing tonic strengh in estuaries was well explained by the developed model.
5.Behavior of ecosystem at the river mouth was estimated by the tidal flat model. It was found that microalgae on sediment decrease the accumulation of organic matters in the model. Furthermore, the model showed flow of organic matter in bivalve-dominant system become more active than that in control system. Therefore, bivalves might be useful to inhibit the accumulation of organic matters.
6.A physical model of staratification and mixing in closed bay was developed. The heat balance and water exchange at bay mouth were taken in consideration. The results show good agreement with observation.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), TOHOKU UNIVERSITY, 14205069

Sediment budget analysis for large areas in Japan
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
2002 - 2004
TANAKA Hitoshi; UCHIJIMA Kunihide; KUROKI Mikio; SASAKI Mikio; SAKAI Shigeki; MATSUTOMI Hideo
Severe erosion has been observed in many coastal area in Japan, partly due to reduction of sediment supply from river basin, and partly due to interruption of sediment movement due to coastal structures. Sediment budget analysis has been carried out for large areas in Japan, by organizing a research group covering whole of the country from Hokkaido to the western part of Japan. Furthermore, the research area has been extended to foreign country. Since it is important to introduce whole of the research results, some of the primary results will be described.
1.Based on long-term shoreline survey data on Sendai Coat located in northeast of the main land in Japan, sediment budget analysis has been carried out successfully. Especially, longshore distribution of sediment transport rate has been well estimated by considering factors such as sediment loss into the offshore direction and interruption of longshore sediment movement caused by offshore breakwaters. Similar long-term accumulation of shoreline survey data is highly recommended foe precise sediment budget analysis.
2.Long-term bathymetric data on Ishinomaki Coast has been analyzed for evaluating effect of headlands construction along the coast. It is found that the coastal morphology reached its equilibrium in the very recent years, except the down drift end of the study area where the mouth of the Naruse River is located. Due to the reduction of the sediment supply to the mouth, severe erosion of the sand spit can be observed.
3.Similar problem of sand spit intrusion can be seen at several river mouths such as Sagami, Ohyodo and Watari Rivers. In order to clarify such a complicated processes, equilibrium condition for cross sectional area at a river entrance. According to the process-based modeling developed herein, it is shown that the equilibrium condition can be described by two dimensionless parameters indicating relative importance of river and coastal sedimentations. The model results are applied to river mouths in Japan, and its applicability has been confirmed. Similar modeling will be useful for estimating sedimentary environment at a river mouth under combined influence of waves, river discharge and tides.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tohoku University, 14350262

小規模河床波に関する研究
2001
Competitive research funding

The formation of dunes and ripples
2001
Competitive research funding

Summarizing of river mouth processing method based on comparative study on river mouth in Japan
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A).
1998 - 2000
TANAKA Hitoshi; UCHIJIMA Kunihide; MANO Akira; SAWAMOTO Masaki; TOHMA Satoshi; KUROKI Mikio
There have been several countermeasures against river mouth blockage due to high waves, such as training jetties, gate, culvert and artificial dredging. The relative advantages and disadvantages of each method are summarized based on a numerous field observations at various river mouths in Japan. Among these, it is noted that an artificial dredging method has quite less influence to adjacent coastal and estuarine environments. But, the presence of sand spit at a river mouth interrupts effluent flood flow into the sea. An appropriate flushing of the sand spit can reduce flooding intensity in the adjoining areas. Initial sand spit elevation influences initiation and development of flushing through a complex interaction of effluent flood discharge, tidal level and sediment transport processes. To investigate this complicated process, a numerical computation method is developed. After verification, it is used to investigate the influence of initial sand spit level on the time-variation of river stage and corresponding development of bed topography under the actions of both tide and high flood flow. Furthermore, sedimentation process around a river mouth is studied in connection with sand budget in a river basin and beach processes.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A)., Tohoku University, 10305036

海底乱泥流による海底峡谷の形成機構に関する研究
2000
Competitive research funding

The formation of submarine canyons due to turbidity currents
2000
Competitive research funding

地形の形成と土砂移動現象の長期予測に関する研究
科学研究費助成事業 奨励研究(A)
1999 - 1999
泉 典洋
日本学術振興会, 奨励研究(A), 東北大学, 11750449

Research on Free Meandering and Channel Width Formation in Channels with Mixture Grain Size Bed Material
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
1998 - 1999
SHIMIZU Yasuyuki; BABA Hitoshi; IZUMI Norihiro; SEKINE Masato
Fine sand deposition on a floodplain during the Abukuma River flood in 1998 is studied both observationally and theoretically. It is found from the observation that most of the deposition consists of fine sand of about 0.1 mm in diameter, which is commonly refer to washload that is not included in bed material. The observed data shows that the deposition is maximized around 10 m inside of the floodplain along the boundary between the main channel and the floodplain. This phenomenon is found to be well-explained by the theory of suspended sediment transport. The predicted value of the magnitude of the deposition agrees well with the observed value with the use of suspended sediment concentration obtained in another observation.
A numerical model is proposed to investigate free meandering of river. Flow field, bed deformation, bank erosion and channel migration are calculated numerically with a general non-orthogonal coordinate system which can be applied to moving boundary conditions. Flow field is calculated from two dimensional momentum equations and continuity equation. Bed deformation is calculated from continuity equation of bed load transport. Bank erosion and deposition is estimated from critical slope of bank material and emergence of bed due to the bed deposition. Time dependent change of channel geometry is calculated with an iteration process of these procedures. Calculated results are favorably compared with experimental results with movable bed and bank, and thus the accuracy of new model is verified.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), HOKKAIDO UNIVERSITY, 10650497

Construction of the sediment transport model covering whole catchment area
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
1998 - 1999
MANO Akira; NAGABAYASHI Hisao
Mano dealt with the Abukuma River and constructed channel network with 500m-grid size covering the whole catchment area. They have developed the system to compute the runoff on the network with the kinematic wave approximation and by inputting the distributed rainfall based on the AMeDas observation. They then have developed a sediment transport model on the same network by using the flow field obtained by the runoff analysis and by considering the physical processes of erosion, settling and convection. The model is shown to have high accuracy through the comparison with the observation.
Izumi executed field survey on the wash load carried by the flood of the Abukuma River in 1998 and has shown that spilled flood into the flood channel made significant deposition near the central edge like a natural bank and the grain size distribution became finer toward the other edge. He has developed the theory on the suspended load transport and shown that the observed distributions of sedimentations and grain size are explained by the theory.
Nagabayashi studied the transport of nitrogen, phosphorus and turbidity material in the Abukuma River. The characteristics of their concentration are investigated for floods and usual currents. During floods, turbidity has high correlation with the concentration of total nitrogen and total phosphorus. The ratios of the dissolved components to the total nitrogen and total phosphorus are shown to significantly change depending on the concentration of these total quantities. It suggests the ratios are effective to determine these loads.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), TOHOKU UNIVERSITY, 10650498

生息環境水理学の展開のための調査研究
科学研究費助成事業 基盤研究(C)
1998 - 1998
辻本 哲郎; 後藤 仁志; 泉 典洋; 渡辺 明英; 清水 義彦; 村上 正吾
平成9年に河川法が改正され,治水,利水に加えて親水,自然環境保全機能も河川整備・管理の目的と認識されるようになってきた.このなかで河川の自然復元は今日的課題としてちゅ木を浴び,河川水理はこれを支えるべきと考えられている.すなわち旧来的なかいすい路水理学を基礎に,移動床水理,植生水理,生息環境水理を融合したものを河川水理学として発展させ,学術の成果を技術にいかすことが求められている.本研究では,とくに「生息環境水理学」の展開をにらんでその体系化を探った.
ほとんどの河川の生息環境は,水流,土砂輸送,地形変化,植生の相互作用の各サブシステムならびに総合システムとして構成されており,植生の存在やその盛衰に関連した移動床過程の記述・予測が不可欠と考えられた.こうした観点から,植生を伴う流れを離散粗度として運動量のみならず乱れエネルギー修士に関わる式にまで及んでモデル化した取り扱いを基礎に,植生周辺での移動床過程が研究された.さらに,洪水時の地形変化と洪水後の植生の繁茂の繰り返しに着目した研究が行われ,洪水・低水の繰り返しの重要性が認識された.
一方,生態系保全機能を治水・利水機能と等しく認識するための機能評価手法についての研究が進められた.とくに水理諸量,地形,植生,底質などと生息環境の適否を関連づけ(PHABSIM/Physical habitatsimulation),流量の変動に対して生息環境としての適正値がどのように変化するかを評価するシナリオ(IFIM/Instream Flow Incremental Methodology)が注目された.
本研究では,解析的あるいは実験的な方法で進められるとともに,フィールド調査を行いながら,現地調査法を整えること,数値解析,実験水路での基礎実験とフィールド調査をどのように関連づけたり補完させて,生息環境水理学の基礎学術としての確立とともに,環境影響評価の手法にいかすなど応用面についての展望についても検討を行った.
日本学術振興会, 基盤研究(C), 名古屋大学, 10895012

Analysis on sediment transport under wave action as particle-fluid interacting system
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
1996 - 1998
SAWAMOTO Masaki; GOTOH Hitoshi; IZUMI Norihiro; TANAKA Hitoshi
Aiming an application to the sediment transport analysis in sheet flow regime, basic mechanism of sediment-fluid interaction were studied from various view points.
Sawamoto carried out two kind of experiments. In the first, fluid force exerting on particles were measured in dense mixture flow and a diagram of drag coefficient was proposed. In the second, velocity distributions of partic1e flow in steep chute were observed and shear stress was formulated.
Tanaka analysed turbulent structure and bed shear stress under random wave action. Applying a spectral analysis, significant progress was achieved. The results were compared with experiments and k-epsilon model and reliability was checked.
Izumi investigated the interaction between flow and movable beds theoretically. Formulating the stability of bed erosion by linear theory, it was shown that space of gullies is controlled by fluid-bed stability.
Gotoh studied the effect of granular characteristics of sediment from two view points. At first, a series of experiments on collision between movable bed and saltationg particle were carried out. The results were utilized in the simulation. Secondly, particle movements were simulated by Lagrangian method.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), TOHOKU UNIVERSITY, 08455225

湖沼或いは貯水池に流入した濁水によって誘起される乱流混合現象に関する研究
科学研究費助成事業 奨励研究(A)
1996 - 1996
泉 典洋
貯水池内の水は上層ほど温度が高い温度成層を形成している.この成層化した貯水池に洪水で発生した濁質を大量に含んだ濁水が流入すると,貯水池の躍層部や水底に濁水層を形成する.このとき流入した濁水の温度が濁水層より上層の温度より高いと濁水は上昇し対流を形成する.このような温度と濁度という二つの異なる物質による拡散は二重拡散現象の一種である.本研究では,温度を制御するのが困難であるため塩水を用いて密度成層を作り実験を行った.実験では密度成層中に流入する濁水の挙動についてビデオを用いた詳細な観察を行うと同時に,水槽内の水をサンプリングすることによって塩分濃度及び密度を速度し成層中における濁水の挙動を明らかにした.実験によって得られた主たる成果は以下の通りである.
(1)成層中に流入した濁水は濁質を沈降させるとともに密度を減少させる.これによって浮力を得た濁水の一部はフィンガリングを起こしながら成層中を上昇していく・このときのフィンガリングの水平方向スケールは1cm内外,鉛直スケール(長さ)は1-3cm程度であった.また,このようなフィンガリング現象は濁水層より上方の水が連続成層を形成している時のみ見られる現象であり,階段状の成層の場合には見られなかった.
(2)フィンガリングによる対流によって濁水と成層が激しく混合する層(混合層)が形成されるが,濁水層内部では上方ほど濁度が高く,上方ほど塩分濃度が高い状態が形成されている.濁度と塩分濃度を合わせた全体の密度は下方ほど大きくなっており一時的に安定な成層を形成しているが,濁水の上昇が弱まり濁質の沈降が進行すると,塩分濃度の逆勾配による不安定が生じ間欠的な対流が発生する.特にフィンガリングが停止して混合層の上面が下降する際には混合層の上方に,ある一定の鉛直スケールを持った対流セルが形成され,これによって明瞭な不連続層が幾つも形成される.
日本学術振興会, 奨励研究(A), 東北大学, 08750621

Study on stability of organized horizontal vortices and sediment transport in compound open channel flow
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
1995 - 1996
IKEDA Syusuke; IZUMI Norihiro; YAGI Hiroshi
It has been known that shear instability generates large horizontal vortices at the junctions of main channel and flood plains in two-stage channel. A series of laboratory tests were performed by varying the main channel width, and the tests were conducted for 3 cases of water depth. Fluid velocity and water surface elevation were measured by using laser-Doppler velocimetry and capacity-type wave gage, respectively. It was found that two arrays of vortex streets become very stable at b/H=5, in which b is main channel width and H is main channel depth. The Reynolds stress at the junction shows a peak value at b/H=5 for all cases of water depth. The wavelength of vortices was predicted successfully in terms of linear instability analysis.
A series of laboratory tests were also performed in open channel flows with bank vegetation, in which the flow fields become more 2-dimensional than compound open channel flow. Similarly in compound open channel flow, when the vortex streets becomes stable staggered array, the Reynolds stress takes a peak value. The peak value of Reynolds stress is larger than that of compound open channel flow. A numerical computation employing SDS and 2DH turbulence model originally proposed by Nadaoka and Yagi was performed to calculate the 2-dimanesional flow field, supporting the measurements.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo Institute of Technology, 07455195

Development of Automatic measurement system of the instantaneous 3-dimensional flow field by using PIV and MASCON model
Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
1995 - 1996
IKEDA Syusuke; KANDA Manabu; IZUMI Norihiro
An advanced technique using PIV and MASCON model was developed to measure the instantaneous 3-dimensional flow field above flexible water plant. The measurement reveal that organized vortices are generated intermittently above the vegetation. A side view of the vortex shows an elliptical shape, and the part of the 3-dimensional structure above the vegetation layr consists of a pair of vortices inclined downward toward the front. The period of the vortex generated is explained in terms of linear stability analysis of flows with an inflectional velocity profile. The wavy motion of flexible vegetation is induced by movement of such organized vortices. The instantaneous flow field was visualized by using Application Visualization System effectively. It was confirmed that the technique developed in this study is a powerful tool to measure the 3-dimansional and unsteady flow field.
To obtain the transport of fluid momentum and sensible heat induced by the organized vortices above the flexible plant, a field observation was conducted at a reed field. The observation suggests that the organized vortices are the major agency for exchange of fluid momentum, heat and other substance between in and above plant canopy.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Tokyo Institute of Technology, 07555451

河口デルタの形成機構と海水面上昇がそれに及ぼす影響に関する理論的・実験的研究
科学研究費助成事業 奨励研究(A)
1995 - 1995
泉 典洋
近年、地球温暖化による水循環環境の変化が危惧されているが、それによる海水準面の上昇によって河口デルタが大きな影響を受けることは必至である。本研究は、河口デルタの形成メカニズムを明らかにし、下流端境界条件である海水準面の変動が河口デルタの形成過程にどのような影響を及ぼすのかを定量的に明らかにすることを最終的な目的として行われた。その第一段階として、次のような成果を得ている。
(1)幅5cm長さ4mの河川部と幅1.8m長さ2.5mの海岸部を有する実験模型を用いて、移動床実験を行った。河川部上流から給水及び給砂を行うと河口部において堆砂が生じ河口デルタが形成される。本研究の様な、掃流砂のみが生じ波や海浜流の影響がない条件下では、河口デルタは同心円状に発達し、円弧状デルタによく似た形状となることがわかった。
(2)レーザー式変位計を用いて堆積形状の経時変化を測定すると同時に、ビデオカメラを用いてデルタの発達の様子を観察した。その結果、デルタは2次元的な放射状の堆積によって円弧状に発達していくのではなく、1次元的な流路が、分裂による分岐流路の生成、分岐流路の消滅といった過程を伴いながら首振り運動をすることによって、平均として円弧状に発達していくことが明らかとなった。
(3)デルタの2次元的な発達を司る1次元的な流路の力学的特性を理解するために、1次元デルタの形成実験を行った。次の結果、その諸点が明らかとなった。デルタ先端での水深は時間によって変化せず、ほぼ一定の値を保つ。また縦断形状の時間変化も非常にゆっくりとしたものであり、ほぼ同じ形状を保ちながら流下方向に前進する準平衡形状が存在する。
(4)理論解析によって、1次元デルタ準平衡形状の理論解を導いた。理論は実験結果と良好に一致することが示された。
日本学術振興会, 奨励研究(A), 東京工業大学, 07750592

チャンネルネットワークの自己形成機構に関する理論的・実験的研究 -地下水湧出による侵食に着目した線形安定論-
科学研究費助成事業 奨励研究(A)
1994 - 1994
泉 典洋
断層によって生じた崖や河岸部の脚部において生じた湧水は,その湧出面を侵食しガリを形成する.このガリは,更なる侵食の進展によって水路へと発達していく.本研究では,ガリ(初期水路)の形成メカニズムを解明するために,室内実験および理論解析を行った.それによって以下の諸点が明らかとなった.
1.一次元模型と非粘着性の砂を用いた室内実験によって,湧水によって斜面が侵食され後退していく過程が観察された.湧出面上の土砂が湧水によって剥離され,引き続いてその上部の土砂が崩落することによって,斜面は上流側へと後退していく.この斜面の後退速度は,湧出量と相関があることが明らかとなった.
2.二次元模型と石炭粉を用いた室内実験によって,湧水侵食は横断方向に不安定であり,ある一定の間隔でガリが生じることが示された.また,ガリの間隔はガリの発達に伴って広くなっていくことが観察された.これは実際の水路形成の過程でも観察される現象であり,室内実験によっても水路形成の基本的なメカニズムを再現できることが示された.
3.斜面の後退速度を湧出量と関係づけ,地下水流の方程式と組み合わせることによって,湧水による斜面侵食を記述する方程式を得た.この方程式をperturbationとinstability analysisの手法を用いて解析することによって,擾乱の発達初期において最大の発達率を有する波長(卓越波長)が求められた.この波長が,実現するガリの間隔に相当していると考えられる.得られた卓越波長は実験によって得られた波長とおおむね一致した.
日本学術振興会, 奨励研究(A), 東京工業大学, 06750541

study on the effect of urban rivers on micro climate in surrounding region
Grants-in-Aid for Scientific Research Grant-in-Aid for General Scientific Research (B)
1993 - 1994
IKEDA Syunsuke; IZUMI Norihiro
(1) When wind blows across rivers, internal boundary layrs develop in channels and the lower portion of the wind is cooled on water surfaces and flood plains. This cooling effect reaches 30 m high in our observation. The intrusion of this cooled wind results in the drop of temperature in urban areas.
(2) Heat exchange between the atmosphere and flood plains is maximized in the daytime, and it is larger when sea wind blows than land wind does. In addition, the heat exchange is correlated to the drop of temperature in urban areas around rivers.
(3) Heat budget on flood plains and water surfaces in urban rivers is studied. Latent heat is dominant in flood plains, while heat storage is dominant in water surfaces. These are the main processes of the cooling effect of rivers.
(4) Under the assumption of hydrostatic pressure, the atmospheric flow in the internal boundary layr is modeled. Numerical simulations are performed to predict wind velocities, temperature and humidity distribution. The predicted results agree well with the observed data.
(5) In tidal rivers, heat budget is strongly effected by the movement of water body. The temperature is oscillating due to tides. It is observed that water temperature in tidal rivers is more uniform than lakes. The temperature difference between surface water and bottom water is as small as 1.5 degrees Celsius. This small difference of temperature increases the cooling effect of rivers.
(6) A numerical model to predict the cooling effect of water surfaces and greenbelts in urban areas is proposed. The simulation using this model can suggest the arrangement of water surfaces and greenbelts in urban areas.
Japan Society for the Promotion of Science, Grant-in-Aid for General Scientific Research (B), Tokyo Institute of Technology, 05452244

Hydraulic Study on Purification Function of Forest-Soil Layr
Grants-in-Aid for Scientific Research Grant-in-Aid for Developmental Scientific Research (B)
1993 - 1994
IKEDA Syunsuke; SHIRAI Akira; YAGI Hiroshi; IZUMI Norihiro
Turbid water flowing into forest area is purified by the forest-soil layr. In this study, mathematical models to quantify this purification function of forest-soil layr were proposed. The process of gully formation which governs the erosion in the mountain area was also investigated. The results are summarized as follows :
(1) It is experimentally shown that fallen leaves on the soil layr can prevent the soil layr from being plugged by suspended sediment.
(2) A model to predict purification of turbidity in forest-soil layr was proposed. This model was combined with a model of two-dimensional unsaturated seepage flow. A numerical simulation for the process of purification was performed. The results of the simulation agree reasonably well with those of the laboratory tests.
(3) The relation between forest-nonforest ratio and the concentation of turbidity in rivers was observed in fields.It is found that the concentration of turbidity is 1000-5000ppm for 0% of forest-nonforest ratio while 100 and 10ppm for 20 and 100% of forest-nonforest ratios, respectively.
(4) It is found that the concentration of turbidity is correlated to that of phosphorus. This implies that nutritious salts as well as turbidity are trapped in forest-soil layr.
(5) A mathematical model for the ability of forest to prevent sand transport due to wind was proposed. The results of the model agree reasonably well with those of the wind tunnel experiments.
(6) Field experiments of turbidity flow were performed. It is found that it is important to render the flow as uniform as possible to prevent piping erosion.
(7) Erosion due to seepage flow on slopes are studied. An instability analysis was performed to obtain the spacing between gullies formed on slopes. The results of the analysis agree reasonably well with those of experiments.
Japan Society for the Promotion of Science, Grant-in-Aid for Developmental Scientific Research (B), Tokyo Institute of Technology, 05555143

水路網の形成機構に関する研究
1993
Competitive research funding

The formation of channel networks
1993
Competitive research funding