Researcher basic information

• 博士（工学）, 北海道大学

• https://researchmap.jp/toshiki_iwasaki?lang=en

• https://jglobal.jst.go.jp/detail?JGLOBAL_ID=201901017996629681
• https://sites.google.com/view/toshiki-iwasaki

• 201901017996629681

• numerical simulation
• morphodynamics
• river engineering
• hydraulic engineering

• 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

Research activity information

• Jun. 2025, 土木学会, 土木学会論文賞
  現況河道の状態把握を起点とした堤防の侵食・洗掘破堤危険度評価手法の実践的開発～2019年10月洪水による千曲川での被災事例を検討対象として～
  戸田祐嗣;岩崎理樹;溝口敦子;磯部良太;鈴木克尚;坂野アイカ;中島由以佳;田中規夫;藤田光一
• Nov. 2019, Committee on Hydroscience and Hydraulic Engineering, Best paper award of annual conference on Hydraulic Engineering JSCE
  Computations of three-dimensional antidunes in rivers
  Toshiki Iwasaki;Takuya Inoue;Shinichiro Onda;Hiroki Yabe
• May 2018, 北海道開発局, 北海道開発技術研究発表会 寒地土木研究所長賞
  三角波による河川管理上のリスク：ブロックの安定性を例として
  岩崎理樹;井上卓也;矢部浩規
• Jun. 2015, 土木学会, Excellent paper award for young scientist, JSCE
  An influence of modelling of secondary flows to simulation of free bars in rivers
  Toshiki Iwasaki
• Mar. 2013, 土木学会 水工学委員会, 水工学論文奨励賞
  浸透流を考慮したTidal Creekの発達過程に関する数値解析
  岩崎理樹
• Mar. 2010, 土木学会 北海道支部, 土木学会北海道支部年次講演会優秀学生講演賞
  混合砂河床におけるTidal Creekの発達過程に関する研究
  岩崎理樹
• Mar. 2008, 北海道大学 土木工学科, 廣井賞
  岩崎理樹
• Mar. 2006, 苫小牧工業高等専門学校 環境都市工学科, 近藤賞
  岩崎理樹

• In situ evidence of self-accelerating turbidity currents
  Hongbo Ma; Gefei Deng; Xingyu Chen; Yuanjian Wang; Brandon McElroy; Jeffrey Nittrouer; Yu Zhang; Toshiki Iwasaki; Matthieu Cartigny; Xudong Fu
  Proceedings of the National Academy of Sciences, 123, 22, National Academy of Sciences, 26 May 2026, [Peer-reviewed]
  English, Scientific journal, Self-accelerating turbidity currents (SATCs) are hypothesized to be the primary mechanism for transporting vast amounts of sediment to the deep ocean. However, theoretical predictions of SATCs have preceded field observations by decades, leaving a critical gap in our understanding of this long-distance delivery process. Here, we present results from a four-year field survey of turbidity currents and bathymetric evolution in the Xiaolangdi Reservoir on the Yellow River (China), the world’s most sediment-laden river. We provide definitive in situ evidence of SATCs, characterized by synchronous down-channel increases in sediment mass and current momentum, alongside massive channel incision at the event scale. Notably, these SATCs occur in a low-gradient lacustrine setting, challenging the prevailing hypothesis that such phenomena are restricted to steep submarine channels or high velocity conditions. We identify a dimensionless threshold, incorporating current velocity, channel slope, and sediment settling velocity, that governs SATC formation across sublacustrine and marine environments. This threshold provides a robust framework for predicting SATC occurrence and informs engineering strategies to sustain reservoir capacity and restore sediment connectivity in dammed river systems.
• MONITORING OF MACROPLASTIC LITTER DEPOSITED ON RIVER BARS: A CASE STUDY OF THE TOYOHIRA RIVER
  Toshiki IWASAKI; Issei OHYA; Kazuki MIYAMA
  Japanese Journal of JSCE, 82, 16, n/a, n/a, Japan Society of Civil Engineers, Feb. 2026, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal
• THE EFFECT OF HYDROGRAPH SHAPES ON RIVER BANK EROSION
  Soichi TANABE; Shun OKOCHI; Toshiki IWASAKI
  Japanese Journal of JSCE, 82, 16, n/a, n/a, Japan Society of Civil Engineers, 2026, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal
• A Lidar-based deep learning framework for driftwood recognition and quantification
  Liu, S.; Isobe, K.; Iwasaki, T.; Shioda, K.; Li, D.
  Proceedings of the 15th International Conference on Geotechnique, Construction Materials & Environment (GEOMATE), Nov. 2025, [Peer-reviewed]
• Upstream‐Migrating Bars in Partially Transporting Straight Channels: Numerical Simulation and Theoretical Interpretation
  Toshiki Iwasaki; Soichi Tanabe; Norihiro Izumi
  Water Resources Research, 61, 10, American Geophysical Union (AGU), 25 Oct. 2025, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal, Abstract
  
  Alluvial bars in straight channels generally migrate downstream or can be non‐migrating but rarely migrate upstream. On the other hand, a recent long‐term field observation suggested a possibility of the upstream migration of bars. To understand this rare morphodynamic feature of alluvial bars, we herein perform non‐linear numerical simulations of alluvial bar formation and development in a straight channel. More specifically, we simulate alluvial bar dynamics under steady discharge and unsteady discharge (repeated hydrographs), wherein the bar regime retains super‐resonance condition. The result shows that initially formed, short downstream‐migrating free bars elongate, becoming much longer upstream migrating bars. The former bar elongation can be understood as a well‐observed non‐linear response of the bars, but much longer bar formation might originate from different morphodynamic features. The theoretical interpretation for this result using temporal and spatial mode linear analysis suggests a sort of forced bar formation in the upstream channel originating from nearly non‐migrating, slow‐movement bars. In other words, nearly non‐migration bars act as forcing factors, similar to an asymmetric obstacle in the channel, leading to an upstream morphodynamic influence observed under super‐resonance conditions. Subsequently, an interaction/coexistence of free‐migrating and forced‐steady bar responses may contribute to the formation of upstream‐migrating bars. These results provide new insights into the migration features of alluvial bars, but they still require a comprehensive theoretical framework to explain them. Additionally, observing upstream‐migrating bars will be an important future research, although it will be difficult due to the considerably slow migration speed predicted by the present numerical simulation.
• Effect of grain-sorting waves on alternate bar dynamics: implications of the breakdown of the hydrograph boundary layer
  Soichi Tanabe; Toshiki Iwasaki
  Earth Surface Dynamics, 13, 4, 723, 743, Copernicus GmbH, 25 Aug. 2025, [Peer-reviewed], [Last author]
  English, Scientific journal, Abstract. Understanding the morphological responses of gravel-bed rivers to changes in external forces (e.g. water and sediment supply conditions) is a critical concern in river science and engineering. However, this remains challenging because river responses depend heavily on the distance from the source point where such environmental changes occur. In this study, we focus on the short-term effects of flood-scale non-equilibrium sediment supply on downstream alternate bar dynamics in poorly sorted gravel-bed rivers using a numerical morphodynamic model. Specifically, a two-dimensional morphodynamic calculation was performed using iRIC-Nays2DH in a straight channel under repeated cycles of an unsteady water hydrograph and a constant supply of poorly sorted sediment. In well-sorted sediment cases, the upstream non-equilibrium sediment supply only affects a limited distance from the upstream end (i.e. the hydrograph boundary layer). However, the inclusion of poorly sorted sediment disrupts this concept and leads to the migration of low-amplitude bedload sheets farther downstream. In this context, the upstream water and sediment boundary conditions may affect far-downstream river dynamics through the migration of bedload sheets. The numerical results showed that the migration of bedload sheets and the associated fine sediment transport substantially affected the alternate bar dynamics and changed their texture. However, this effect of bedload sheets on the bars cannot propagate along the entire channel and disappears completely in alternate bars located further downstream. These results suggest that upstream non-equilibrium sediment supply conditions in poorly sorted sediment play a major role in downstream alternate bar dynamics. However, this effect becomes negligible further downstream because bedload sheets gradually disperse during their migration process into larger and more active morphological features, such as alternate bars.
• Morphological response of gravel bed rivers near a knickpoint: Effect of bars on dynamic equilibrium river profile
  Soichi Tanabe; Toshiki Iwasaki; Yasuyuki Shimizu
  Earth Surface Processes and Landforms, Wiley, 13 Aug. 2024, [Peer-reviewed]
  English, Scientific journal, Abstract
  
  Geomorphological evolution is one of the main factors that increases flood damage in small or medium rivers located in upstream river reaches. These types of flood damage have been increasing at knickpoints where the riverbed slope and river width change abruptly and are likely to cause non‐equilibrium conditions for sediment transport during floods. Therefore, it is important to understand the non‐equilibrium morphological response at the knickpoint and the resulting new dynamic equilibrium state under given external forces. The effects of two‐dimensional (2D) morphological features on the dynamic equilibrium riverbed profile, however, have not been specifically studied because the methods currently in use for calculating equilibrium profiles are based on zero‐ or one‐dimensional (0D or 1D) modeling. Here, we perform numerical calculations using the 2D morphodynamic model iRIC‐Nays2DH to clarify the dynamic equilibrium profile and the process of reaching a dynamic equilibrium state. We also use an existing 1D model to show the 2D effect in the dynamic equilibrium state. To understand this, we set up three channels: slope transition point, width transition point, and both the slope and width transition point. 1D results show a constant slope profile in channels with constant width and upward‐convex profiles in channels with width expansion at the equilibrium state, owing to the adjustment of the difference in sediment transport volume in the two reaches with different widths by changing the slopes. In contrast, the 2D results show that the alternate bars create a small autogenic knickpoint even in the straight channel and significantly dampen sediment deposition at the width expansion point, as seen in the 1D model result. This was because the bars' shape increased the volume of sediment transport because the shape of the bars concentrated flow. These results suggest that 2D morphological features, such as fluvial bars, play a significant role in the equilibrium riverbed profile.
• Assessment of risks associated with development of river meandering under climate change using a physics-based free-meandering model
  Shigekazu Masuya; Takuya Inoue; Toshiki Iwasaki; Riho Kido; Kohei Ogawa; Yasuyuki Shimizu
  Environmental Fluid Mechanics, Springer Science and Business Media LLC, 21 Jun. 2024, [Peer-reviewed]
  English, Scientific journal, Abstract
  
  Recent increases in heavy rainfall events, which may have resulted from climate change, have caused various natural water- and sediment-related disasters. A typical sediment-related disaster in a steep gravel-bed river is extreme bank erosion and subsequent meander development, damaging residential areas and infrastructure along the river. Assessing the bank erosion rate and its future changes under climate change is essential to prevent such severe disasters. Here, we propose a simple but useful framework for this purpose using a physics-based numerical model of free meandering and a large dataset of flood hydrographs generated from climate and runoff models. First, numerical experiments on meandering development were conducted using a two-dimensional morphodynamic model of free meandering. The results indicate that meander dynamics could reach a dynamic equilibrium state under several hydraulic and channel geometry conditions, and the characteristics of the simulated meandering channel were reasonably consistent with the field data. The meander amplitude of this state was positively correlated with the steady discharge; therefore, the increase in flow discharge may have an important effect on river dynamics under climate change. To quantify this effect, we combined a simple predictor of meander amplitude derived from a numerical experiment with a flood hydrograph dataset for current and future climatic conditions. The results suggest that the meander amplitude increased significantly for the same probability of occurrence; therefore, the risk of riverbank erosion due to river meandering will increase significantly under future climate conditions.
• DISCUSSIONS OF BAR GROWTH RATE AND DEVELOPMENT OF BAR HEIGHT ESTIAMATION METHOD
  Takuya INOUE; Toshiki IWASAKI; Tamaki SUMNER; Yuki HIRAMATSU; Toshihisa OZEKI; Shunichi SASAKI; Tatsuro TOMINO; Riho KIDO
  Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, Feb. 2024, [Peer-reviewed]
  Scientific journal
• PRACTICAL DEVELOPMENT OF A RISK EVALUATION METHOD FOR EROSION TYPE LEVEE BREACH BASED ON THE EXISTING RIVER CONDITIONS ~ CASE OF DAMAGE IN THE CHIKUMA RIVER IN THE OCTOBER 2019 FLOOD ~
  Yuji TODA; Toshiki IWASAKI; Atsuko MIZOGUCHI; Ryota ISOBE; Katsuhisa SUZUKI; Aika BANNO; Yuika NAKAJIMA; Norio TANAKA; Koichi FUJITA
  Japanese Journal of JSCE, 80, 7, n/a, n/a, Japan Society of Civil Engineers, 2024, [Peer-reviewed]
  Scientific journal
• Morphodynamic equilibrium of alternate bar dynamics under repeated hydrographs
  Dai Huang; Toshiki Iwasaki; Takashi Yamada; Yuki Hiramatsu; Satomi Yamaguchi; Yasuyuki Shimizu
  Advances in Water Resources, 104427, 104427, Elsevier BV, Mar. 2023, [Peer-reviewed]
  English, Scientific journal
• Effect of Sediment Supply on Morphodynamics of Free Alternate Bars: Insights from Hydrograph Boundary Layer
  Huang Dai; Toshiki Iwasaki; Yasuyuki Shimizu
  WATER, 13, 23, Dec. 2021, [Peer-reviewed], [International Magazine]
  English, Scientific journal
• Recent advances on bedform research and application: Process-based to machine learning
  Sanjay Giri; Amin Shakya; Mohamed Nabi; Suleyman Naqshband; Toshiki Iwasaki; Satomi Yamaguchi; David C Froehlich; Biswa Bhattacharya; Yasuyuki Shimizu
  EGU General Assembly Conference Abstracts, Apr. 2021
  English
• The Role of Large-Scale Bedforms in Driftwood Storage Mechanism in Rivers
  Takara Okitsu; Toshiki Iwasaki; Tomoko Kyuka; Yasuyuki Shimizu
  WATER, 13, 6, Mar. 2021, [Peer-reviewed], [Corresponding author], [International Magazine]
  English, Scientific journal
• EXPERIMENT ON EFFECT OF POSITIONAL RELATIONSHIP BETWEEN IN-CHANNEL SUPPLIED SAND AND SANDBARS ON THE TRANSPORT PROCESS
  平松裕基; 山口里実; 岩崎理樹
  土木学会論文集 B1(水工学)(Web), 77, 2, 2021, [Peer-reviewed]
• EXPERIMENTS ON THE EFFECT OF RIVERBANK VEGETATION ON THE CHANNEL MORPHOLOGY - THE CASE THAT THE ROOTS ARE SHORT RELATIVE TO THE BANK HEIGHT -
  Satomi YAMAGUCHI; Tomoko KYUKA; Takaaki MINAMI; Yasuyuki SHIMIZU; Toshiki IWASAKI
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77, 2, I_721, I_726, Japan Society of Civil Engineers, 2021, [Peer-reviewed]
  Scientific journal
• A storm-induced flood and associated nearshore dispersal of the river-derived suspended ¹³⁷Cs
  Yusuke Uchiyama; Natsuki Tokunaga; Kohei Aduma; Yuki Kamidaira; Daisuke Tsumune; Toshiki Iwasaki; Masatoshi Yamada; Yutaka Tadeda; Takashi Ishimaru; Yukari Ito; Yutaka W. Watanabe; Ken Ikehara; Miho Fukuda; Yuichi Onda
  Science of the Total Environment, 2021, [Peer-reviewed], [International Magazine]
  English, Scientific journal
• Three-dimensional antidunes coexisting with alternate bars
  Takuya Inoue; Yasunori Watanabe; Toshiki Iwasaki; Junichi Otsuka
  EARTH SURFACE PROCESSES AND LANDFORMS, 45, 12, 2897, 2911, Sep. 2020, [Peer-reviewed]
  English, Scientific journal
• FLUME EXPERIMENTS AND NUMERICAL COMPUTATION ON REVETMENT FAILURE DUE TO BED DEFORMATION IN MEANDERING CHANNEL
  奥田醇; 清水康行; 久加朋子; 岩崎理樹
  土木学会論文集 B1(水工学)(Web), 76, 2, 2020, [Peer-reviewed]
• A case study of flood modeling with adaptive mesh refinement
  Wentao Gong; Yasuyuki Shimizu; Toshiki Iwasaki
  22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020, [Peer-reviewed]
  English, International conference proceedings
• Numerical Simulation of Colored Sand Transport Process Using Bedload Tracer model
  山田嵩; 岩崎理樹; 矢部浩規
  寒地土木技術研究, 806, 2020
• ESTIMATION OF CHANNEL WIDTH OF A RIVER UNDER CLIMATE CHANGE
  舛屋繁和; 井上卓也; 岩崎理樹; 清水康行
  河川技術論文集, 26 (CD-ROM), 2020, [Peer-reviewed]
  Scientific journal
• The role of saltwater and waves in continental shelf formation with seaward migrating clinoform
  Toshiki Iwasaki; Gary Parker
  Proceedings of the National Academy of Sciences of the United States of America, Jan. 2020, [Peer-reviewed], [Invited], [Lead author], ［Internationally co-authored］, [International Magazine]
  English, Scientific journal
• Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software
  Shimizu Yasuyuki; Nelson Jonathan; Ferrel Kattia Arnez; Asahi Kazutake; Giri Sanjay; Inoue Takuya; Iwasaki Toshiki; Jang Chang-Lae; Kang Taeun; Kimura Ichiro; Kyuka Tomoko; Mishra Jagriti; Nabi Mohamed; Patsinghasanee Supapap; Yamaguchi Satomi
  EARTH SURFACE PROCESSES AND LANDFORMS, 17 Jul. 2019, [Peer-reviewed], [Invited], ［Internationally co-authored］, [International Magazine]
  Scientific journal
• Bedrock-alluvial streams with knickpoint and plunge pool that migrate upstream with permanent form
  Zhang Li; Iwasaki Toshiki; Li Tiejian; Fu Xudong; Wang Guangqian; Parker Gary
  SCIENTIFIC REPORTS, 9, 16 Apr. 2019, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
  Scientific journal
• INVESTIGATIONS OF THE BEDLOAD SEDIMENT TRANSPORT IN A NATURAL RIVER USING IC-TAG MONITORING TECHNIQUE AND NUMERICAL SIMULATIONS
  濱木道大; 岩崎理樹; 井上卓也; 清水康行
  河川技術論文集, 25, 2019, [Peer-reviewed], [Domestic magazines]
  Scientific journal
• MEASUREMENTS OF BED TOPOGRAPHY, WATER SURFACE PROFILE AND VELOCITY FIELD UNDER THE PRESENCE OF TRIANGLE-SHAPE WATER SURFACE WAVE
  井上卓也; 岩崎理樹; 矢部浩規
  土木学会論文集 B1(水工学)(Web), 75, 2, 2019, [Peer-reviewed], [Domestic magazines]
  Scientific journal
• ON THE UPSTREAM-MIGRATING SAND BARS
  岩崎理樹; 矢部浩規
  土木学会論文集 B1(水工学)(Web), 75, 2, 2019, [Peer-reviewed], [Lead author, Corresponding author], [Domestic magazines]
  Scientific journal
• NUMERICAL SIMULATIONS ON THE EVOLUTION OF REAL-SCALE MEANDERING RIVERS
  舛屋繁和; 井上卓也; 岩崎理樹; 清水康行
  土木学会論文集 B1(水工学)(Web), 75, 2, 2019, [Peer-reviewed], [Domestic magazines]
  Scientific journal
• Fundamental study on the performance of blocks for closure of river levee breaches
  岩崎 理樹; 岡部 博一; 島田 友典; 矢部 浩規; 米元 光明
  寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report, 786, 11, 20, 土木研究所寒地土木研究所, Nov. 2018
  Japanese
• Numerical simulation of bedload tracer transport associated with sand bar formation, bank erosion, and channel migration
  Toshiki Iwasaki; Satomi Yamaguchi; Hiroki Yabe
  E3S Web of Conferences, 40, 05 Sep. 2018, [Peer-reviewed], [Lead author, Corresponding author]
  International conference proceedings
• A study on the 2016 August flood and levee breaches in the Sorachi River, Hokkaido, Japan
  Jun Okuda; Yasuyuki Shimizu; Tomoko Kyuka; Toshiki Iwasaki; Yoshiaki Ishida
  Proceedings - International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018, 2, 1007, 1014, 01 Sep. 2018, [Peer-reviewed]
  International conference proceedings
• NUMERICAL SIMULATION OF BEDLOAD TRACER TRANSPORT BY CONSIDERING VERTICAL TRACER DISPERSION
  濱木 道大; 岩崎 理樹; 井上 卓也; 清水 康行
  水工学論文集 Annual journal of Hydraulic Engineering, JSCE, 63, I_955, 960, 土木学会, 2018, [Peer-reviewed]
  Japanese, Scientific journal
• COMPUTATIONS OF THREE-DIMENSIONAL ANTIDUNES IN RIVERS
  岩崎 理樹; 井上 卓也; 音田 慎一郎; 矢部 浩規
  水工学論文集 Annual journal of Hydraulic Engineering, JSCE, 63, I_643, 648, 土木学会, 2018, [Peer-reviewed], [Lead author, Corresponding author]
  Japanese, Scientific journal
• EXPERIMENTS ON THE BLOCK STABILITY UNDER THE PRESENCE OF TRIANGLE-SHAPE WATER SURFACE WAVES IN RIVERS
  IWASAKI Toshiki; INOUE Takuya; YABE Hiroki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_1207, I_1212, 公益社団法人 土木学会, 2018, [Peer-reviewed]
  Japanese, Scientific journal,  In this study, we investigate the effects of the triangle-shape water surface waves induced by the river antidunes on the stability of concrete block, which is a modelled river revetment work. The water surface waves cannot develop over a fixed flat bed even if we obtain a hydraulic condition, which allows the development of surface waves under a movable bed. The comparision of the block stability experiments between fixed and movable bed under same hydraulic condition therefore obtain the destabilizing effect of the surface wave on the block. The experimental results shows that the presence of the triangle-shape water surface wave significantly destabilizes the block installed on the bed because of the occurance of high velocity induced by the waves and an upward flow from the trough to crest of the antidunes.
• INFLUENCE OF SEDIMENT DYNAMICS IN RIVER CHANNEL ON THE CHANNEL CHANGE
  YAMAGUCHI Satomi; KYUKA Tomoko; SHIMIZU Yasuyuki; IZUMI Norihiro; WATANABE Yasuharu; IWASAKI Toshiki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_1153, I_1158, 公益社団法人 土木学会, 2018, [Peer-reviewed]
  Japanese,  Large-scale bank erosion caused by channel change during flood often causes serious disasters in gravel bed rivers. In this study, we focused on the influence of sediment dynamics in river channel on the channel change inducing bank erosion. From the results of sediment balance in the Pekerebetsu River and the Otofuke River during a flood, we showed the possibility that sediment supply from the bank affect stream channel change to expand bank erosion in the river. We carried out the experiments on the influence of sediment supply from the bank on the channel change, and showed that sediment supply from the bank can be a cause of channel change inducing large-scale bank erosion.
• EXPERIMENT AND NUMERICAL SIMULATION OF ADVECTION-DISPERSION OF BEDLOAD TRACERS
  HAMAKI Michihiro; IWASAKI Toshiki; INOUE Takuya; SATO Daisuke; SUMNER Tamaki; SHIMIZU Yasuyuki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_1033, I_1038, 公益社団法人 土木学会, 2018
  Japanese, Scientific journal,  Understanding and predicting of the bedload transport processes in rivers are of great importances for better sediment management works. In this study, we propose a numerical model to understand the bedload transport processes by simulating passive bedload tracer particles. A movable bed experiment with the use of colored bedload tracers is performed to understand the advection-dispersion processes of the tracers, i.e., how the tracer particles transport and disperse over the movable bed. We numerically reproduce observed behaviors of the bedload tracers by using a flux-type tracer transport model combined with a two-dimensional bed evolution model. The experimental results suggest that the bedload mixing process associated with a small-scale bedform dominates the advection-dispersion of tracers. The appropriate determination of the active layer thickness by considering this vertical bedload mixing process is necessary to reproduce the tracer advection speed.
• Hydrogeomorphological differentiation between floodplains and terraces
  Qina Yan; Toshiki Iwasaki; Andrew Stumpf; Patrick Belmont; Gary Parker; Praveen Kumar
  Earth Surface Processes and Landforms, 43, 1, 218, 228, 01 Jan. 2018, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
  English, Scientific journal
• Modeling of the Advection-Dispersion of Bedload Tracers
  岩崎 理樹; 川村 里実; 矢部 浩規
  寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report, 774, 2, 10, 土木研究所寒地土木研究所, Nov. 2017
  Japanese
• Numerical simulation of large-scale bed load particle tracer advection-dispersion in rivers with free bars
  Toshiki Iwasaki; Jonathan Nelson; Yasuyuki Shimizu; Gary Parker
  JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 122, 4, 847, 874, Apr. 2017, [Peer-reviewed]
  English, Scientific journal
• THE EFFECT OF CHANNEL WIDTH AND CHANNEL BED SLOPE ON LEVEE BREACH PROCESSES
  SHIMADA Tomonori; WATANABE Yasuharu; OKABE Kazuhiro; IWASAKI Toshiki; NAKASHIMA Yasuhiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_1345, I_1350, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
  Japanese, It is important mitigating flood damage by overflow from a levee breached. The mechanism of levee breach has not been clarified. This study aims to clarify the below point, the effect of channel width and channel bed profile on levee breach processes by using a numerical model to simulate levee breaches based on results of the experiments. The results of the simulation are as follows: In the case of steep slope channel, levee breach widening is dominant. In the case of mild-slope channel, river bed erosion is dominant.
• CLASSIFICATION OF LEVEE BREACH PROCESSES ACCORDING TO CHANNEL BED SLOPE AND CHANNEL WIDTH
  SHIMADA Tomonori; WATANABE Yasuharu; OKABE Hirokazu; IWASAKI Toshiki; NAKASHIMA Yasuhiro
  Advances in River Engineering, 23, 411, 416, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
  Japanese, It is important mitigating flood damage by overflow from a levee breached. The mechanism of levee breach has not been clarified. This study aims to clarify the below point, the effect of channel bed profile and channel width on levee breach processes by using a numerical model to simulate levee breaches based on results of experiments using the Chiyoda Experimental Channel. The results of the simulation are as follows: In the case of steep slope channel, levee breach widening is dominant. In the case of mild- slope channel, river bed erosion is dominant.
• INVENTORY ANALYSIS OF SUSPENDED RADIOCESIUM DERIVED FROM NIIDA RIVER DURING A TYPHOON-INDUCED FLOOD EVENT
  UCHIYAMA Yusuke; ADUMA Kohei; ODANI Sachika; IWASAKI Toshiki; TSUMUNE Daisuke; KAMIDAIRA Yuki; SHIMIZU Yasuyuki; ONDA Yuichi
  Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 73, 2, I_685, I_690, 公益社団法人 土木学会, 2017, [Peer-reviewed]
  Japanese,  Niida River is well know to supply highly contaminated suspended ¹³⁷Cs originated from the Fukushima Nuclear Power Plant to the ocean. We examine the oceanic dispersal and inventories of the sediments and suspended ¹³⁷Cs in the ocean floor derived from Niida River, using the quadraple nested JCOPE2-ROMS 3D circulation model in a very high resolution configuration, coupled with a 3D multi-class sediment transport model, the iRIC-Nays 2DH river sediment model, the SWAN spectral wave model, and a static ¹³⁷Cs absorption model. We focus on the storm and flood event associated with Typhoon 201326 (Wipha) passed off the Fukushima Coast, which provoked an enomous amount of riverine fluxes, to quantitatively assess the accumulation and erosion of the sediments and resultant suspended ¹³⁷Cs inventories around the river mouth and nearshore areas.
• THE EFFECT OF CHANNEL WIDTH AND CHANNEL BED SLOPE ON LEVEE BREACH PROCESSES
  SHIMADA Tomonori; WATANABE Yasuharu; OKABE Kazuhiro; IWASAKI Toshiki; NAKASHIMA Yasuhiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_1345, I_1350, 公益社団法人 土木学会, 2017
  Japanese,  It is important mitigating flood damage by overflow from a levee breached. The mechanism of levee breach has not been clarified. This study aims to clarify the below point, the effect of channel width and channel bed profile on levee breach processes by using a numerical model to simulate levee breaches based on results of the experiments. The results of the simulation are as follows: In the case of steep slope channel, levee breach widening is dominant. In the case of mild-slope channel, river bed erosion is dominant.
• MODELING THE THREE-DIMENSIONAL RIVER ANTIDUNES: IMPLICATIONS FOR THE TRIANGLE-SHAPE WATER SURFACE WAVE TRAINS
  IWASAKi Toshiki; INOUE Takuya; YABE Hiroki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_901, I_906, 公益社団法人 土木学会, 2017, [Peer-reviewed]
  Japanese,  This study presents a modeling of three-dimensional river antidunes using a Boussinesq model with a non-equilibrium bedload transport model, and discuss the relation of this three-dimensional bedform instability to the triangle-shape water surface wave trains. We performed a linear stability analysis of the three-dimensional antidunes, showing that the proposed model in part reproduces the three-dimensionality of the antidunes. The dominant longitudinal and transverse wave numbers predicted by the analysis are reasonably in agreement with the characteristics of the triangle-shape water surface wave trains, although the model tends to overestimate the wavelength of the water surface waves.
• 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
• Numerical simulation of bar and bank erosion in a vegetated floodplain: A case study in the Otofuke River
  Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  ADVANCES IN WATER RESOURCES, 93, 118, 134, Jul. 2016, [Peer-reviewed], [Lead author, Corresponding author]
  English, Scientific journal
• The international river interface cooperative: Public domain flow and morphodynamics software for education and applications
  Jonathan M. Nelson; Yasuyuki Shimizu; Takaaki Abe; Kazutake Asahi; Mineyuki Gamou; Takuya Inoue; Toshiki Iwasaki; Takaharu Kakinuma; Satomi Kawamura; Ichiro Kimura; Tomoko Kyuka; Richard R. McDonald; Mohamed Nabi; Makoto Nakatsugawa; Francisco R. Simoes; Hiroshi Takebayashi; Yasunori Watanabe
  ADVANCES IN WATER RESOURCES, 93, 62, 74, Jul. 2016, [Peer-reviewed]
  English, Scientific journal
• Sensitivity of free bar morphology in rivers to secondary flow modeling: Linear stability analysis and numerical simulation
  Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  ADVANCES IN WATER RESOURCES, 92, 57, 72, Jun. 2016, [Peer-reviewed]
  English, Scientific journal
• COASTAL DISPERSAL OF RIVER-DERIVED SUSPENDED RADIONUCLIDES DUE TO A FLOOD EVENT AROUND THE MOUTH OF NIIDA RIVER, FUKUSHIMA
  YAMANISHI Takafumi; UCHIYAMA Yusuke; IWASAKI Toshiki; SHIMIZU Yasuyuki; TSUMUNE Daisuke; MISUMI Kazuhiro; ONDA Yuichi
  Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 72, 2, I_757, I_762, 公益社団法人 土木学会, 2016, [Peer-reviewed]
  Japanese,  We examine oceanic dispersal of the iRIC-Nays2DH-evaluated sediment and suspended ¹³⁷Cs influxes from Niida River, Fukushima, with a particular attention to the first flood event in late May of 2011 after the Fukushima nuclear accident. Alongshore suspended ¹³⁷Cs transport occurs assymetrically, comprising storm-driven southward transport confined in the shallow area due to shoreward Ekman transport associated with strong northerly wind, followed by northwestward widespread transport under mild southerly wind condition. About 70 % of the Niida River-derived suspended ¹³⁷Cs remains near the mouth for 20 days after the flood event. Nevertheless, our model results as well as an observation suggest that the area is dominated by erosion as for high bed shear stress all the time, thus suspended radionuclides are redistributed to dissipate away in long term.
• ANTIDUNE INSTABILITY ASSOCIATED WITH A DEPTH-AVERAGED MODEL WITH AN ENTRAINMENT-BASED MODEL
  INOUE Takuya; IWASAKI Toshiki; ONDA Shinichiro
  Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 72, 2, I_565, I_574, 公益社団法人 土木学会, 2016, [Peer-reviewed]
  Japanese, Dynamics of river bedforms which is an interfacial instability phenomenon between turbulent open channel flow and movable bed significantly affect the flow structures and sediment transport dynamics in rivers, so that this have been an classical and important research topic in the field of river engineering. Here, we perform a linear stability analysis for several combinations of flow and sediment transport submodels, specifically, a shallow flow model and a Boussinesq type depth-integrate model for hydrodynamic model, and an equilibrium and a non-equilibrium bedload transport model for sediment mass conservation model. We then investigate how the submodels adopted determine the linear stability and the wavelength of river bedforms. The results show that the combination of the Boussinesq model and the non-equilibrium bedload transport model can explain the antidune instability and its finite wavelength observed in several published experiments, whereas, use of each submodel alone is insufficient to explain the finite wavelength of antidunes.
• Dynamic meandering in response to upstream perturbations and floodplain formation
  F. Schuurman; Y. Shimizu; T. Iwasaki; M. G. Kleinhans
  GEOMORPHOLOGY, 253, 94, 109, Jan. 2016, [Peer-reviewed]
  English, Scientific journal
• NUMERICAL SIMULATION OF TRACER ADVECTION-DIFFUSION UNDER THE INFLUENCE OF FREE BARS
  IWASAKI Toshiki; PARKER Gary; SHIMIZU Yasuyuki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_877, I_882, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
  Japanese, This paper presents numerical simulations of tracer particle transport both in the absence and presence of free bars. The transport and diffusion of tracer particles is affected by both the probabilistic motion of sediment particles and by the river bed geometry associated with free bars. We compare results of numerical models using an equilibrium (flux-based model) and a non-equilibrium (entrainment-based model) conservation formulation for river bed variation associated with bedload transport. The results show that 1) the entrainment-based morphodynamic model successfully reproduces free bar formation, 2) the flux-based morphodynamic model fails to simulate tracer diffusion in the absence of bars, and 3) free bar formation enhances streamwise tracer diffusion.
• APPLICATION OF THE KMR MODEL WITH SPATIAL GEOMETRIC SCALE ON COMPUTATIONS OF RIVER MORPHODYNAMICS
  KIMURA Ichiro; YAMATSUTA Ryo; IWASAKI Toshiki; SHIMIZU Yasuyuki
  STRUCTURAL ENGINEERING / EARTHQUAKE ENGINEERING, 3, 1, 174, 183, Japan Society of Civil Engineers, 2015
  English, A multilevel grid-type turbulent shallow flow model combined with an equilibrium sediment transport model (KMR-MB: Kinematic Mesh Reconstruction for Movable Bed) is proposed. The KMR method is a kind of multilevel grid model with dynamic refinement that combines grid cells to efficiently capture the unsteady flow phenomena. Saito et al. (2012)^1),2) have applied the KMR approach to open channel flows around a bridge pier and have shown the advantage of the model. They used the maximum value of the strain and rotation parameters for the threshold for quadtree and 3×3 grid divisions. We have extended the model for computations of morphological phenomena in rivers by incorporating an equilibrium sediment transport model as well as a bed continuity equation, and used new criteria for grid cell refinement. We used an average curvature of the bed surface as the criteria for refinement and combined quadtree-type grid cells. The present model has been applied to simulate the alternate bar formations. The experimental result by Akahori et al. (2011)³⁾ was used to validate the model. The comparison between numerical and experimental results showed that the present KMR-MB can excellently simulate the phenomena with less CPU time than those computed with the fixed grid.
• A STUDY ON EROSION MECHANISMS OF AGRICULTURAL LAND BY FLOOD FLOWS OF ABU RIVER AT YAMAGUCHI-SHIMANE HEAVY RAIN IN JULY 2013
  AKAHORI Ryosuke; AKAMATSU Yoshihisa; IWASAKI Toshiki; INUI Ryutei; NAGANO Hiroyuki; KAMITSURU Shogo
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_1471, I_1476, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
  Japanese, Semimountainous areas in Yamaguchi and Shimane Prefectures suffered severe damage brought by floods on July 2013. The damages in these areas were characterized by the vulnerability of their backlands that consists of agricultural lands. In order to investigate the mechanisms of land erosion on these areas where existing high-resolution data was not prepared, post-disaster RTK-GPS surveys and numerical simulations were conducted for Abu River in Yamaguchi. The surveys were aimed at providing the high-resolution topographic datasets of these regions in order to evaluate the influences of micro-topography on channel incisions by the flood flow. The results of the numerical calculations of movable bed-evolution well reproduced the process of the channel incisions on these areas, and it implies that the micro-topography is one of the most influential factors on erosion and channel formation processes on such semimountanious regions.
• Computational modeling of Cs-137 contaminant transfer associated with sediment transport in Abukuma River
  T. Iwasaki; M. Nabi; Y. Shimizu; I. Kimura
  JOURNAL OF ENVIRONMENTAL RADIOACTIVITY, 139, 416, 426, Jan. 2015, [Peer-reviewed], [Lead author]
  English, Scientific journal
• A NUMERICAL MODEL FOR SIMULATING TRANSPORT OF RADIOACTIVE CONTAMINANT BY SEDIMENT TRANSPORT IN RIVERS
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 70, 4, I_1267, I_1272, Japan Society of Civil Engineers, 2014
  Japanese, A numerical model for calculating the behavior of radioactive contaminant associated with the sediment transport in rivers has been proposed in this study. The equations for simulating the concentration of radioactive contaminant of the sediment has been derived from the governing equation of the sediment transport model. The proposed model has been applied to a simple river confluence to understand the mixing process of the sediment and the radioactive contaminant in the confluence point. The numerical results provide a useful data for discussing the relation between the bed evolution process and the behavior of radioactive contaminant. In addition, the model can contribute to estimate the origin of the sediment by using the relationship between the simulated sediment diameter and the concentration of the radioactive contaminant.
• A NUMERICAL MODEL FOR SIMULATING TRANSPORT OF RADIOACTIVE CONTAMINANT BY SEDIMENT TRANSPORT IN RIVERS
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_1267, I_1272, 公益社団法人 土木学会, 2014
  Japanese, A numerical model for calculating the behavior of radioactive contaminant associated with the sediment transport in rivers has been proposed in this study. The equations for simulating the concentration of radioactive contaminant of the sediment has been derived from the governing equation of the sediment transport model. The proposed model has been applied to a simple river confluence to understand the mixing process of the sediment and the radioactive contaminant in the confluence point. The numerical results provide a useful data for discussing the relation between the bed evolution process and the behavior of radioactive contaminant. In addition, the model can contribute to estimate the origin of the sediment by using the relationship between the simulated sediment diameter and the concentration of the radioactive contaminant.
• Multi-scale modelling of river morphodynamics
  M. Nabi; S. Giri; T. Iwasaki; I. Kimura; Y. Shimizu
  RIVER FLOW 2014, 1253, 1259, 2014
  English, International conference proceedings
• Numerical study on secondary currents of the second kind in wide shallow open channel flows
  R. Suzuki; I. Kimura; Y. Shimizu; T. Iwasaki; T. Hosoda
  RIVER FLOW 2014, 179, 187, 2014
  English, International conference proceedings
• Modelling of the initiation and development of tidal creek networks
  Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-MARITIME ENGINEERING, 166, 2, 76, 88, Jun. 2013, [Peer-reviewed]
  English, Scientific journal
• APPLICATION OF KMR WITH EFFECT OF SPATIAL SCALE OF GEOMETRY TO COMPUTATIONS ON RIVER MORPHODYNAMICS
  木村 一郎; 山蔦 涼; 岩崎 理樹
  水工学論文集 土木学会水工学委員会 編, 57, 1_643, 648, 土木学会, 2013
  Japanese
• A CONSIDERATION OF CONTROLLING FACTOR ON FORMATION AND DEVELOPMENT OF TIDAL CREEK
  IWASAKI Toshiki; OKUDERA Ryota; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_1093, I_1098, 公益社団法人 土木学会, 2013
  Japanese, This paper presents a consideration of formation mechanism of tidal channel networks. We employed a simple mathematical model to explain the flow and bed evolution in intertidal zones. By assuming the regular periodic tidal wave and the simple bed geometry which has constant slope, we derived an advection - diffusion equation for the bed evolution. This equation has a Peclet type non dimensional number which expresses the ratio between advection and diffusion. We investigated this Peclet number in the experimental results conducted under the different hydraulic conditions. The results show that in the conditions with small Peclet number, which means that the diffusion effect is relatively strong, clear channel network can not develop on the bed surface. On the other hand, in large Peclet number conditions, clear and complicated channel network tends to develop.
• APPLICATION OF KMR WITH EFFECT OF SPATIAL SCALE OF GEOMETRY TO COMPUTATIONS ON RIVER MORPHODYNAMICS
  KIMURA Ichiro; YAMATSUTA Ryo; IWASAKI Toshiki; SHIMIZU Yasuyuki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 4, I_643, I_648, 公益社団法人 土木学会, 2013
  Japanese, A multi-level grid type turbulent shallow flow model combined with an equilibrium sediment transport model (KMR-MB: Kinematic Mesh Reconstruction for Movable Bed) is proposed. KMR method is a kind of multi-level grid model with dynamic refinement and combining grid cells to capture efficiently unsteady flow phenomena. Saito et al. (2012)1) have applied the KMR approach to open channel flows around a bridge pier and shown the advantage of the model. They used the maximum value of the strain and rotation parameters for the threshold for quad-tree and 3 x 3 type grid divisions. We have extended the model for computations of morphological phenomena in rivers by incorporating an equilibrium sediment transport model as well as a bed continuity equation, and employing new criteria for grid cell refinement. We employed an average curvature of the bed surface as the criteria for refinement and combining quad-tree type grid cells. The present model has been applied to simulate the alternative bar formations. The experimental result by Akahori et al (2011)2) was used for validation of the model. The comparison between numerical and experimental results showed that the present KMR-MB can simulate excellently the phenomena with less CPU time than the fixed grid computations.
• A MORPHODYNAMIC MODEL BASED ON A SHALLOW FLOW MODEL AND AN EQUILIBRIUM BEDLOAD TRANSPORT MODEL FOR CALCULATING BED EVOLUTION IN RIVERS
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 3, 123, 134, 公益社団法人 土木学会, 2013
  Japanese, &nbsp;The performance and stability of a numerical model which consist of a shallow water flow model and an equilibrium bedload transport model for calculating bed evolution in rivers is discussed. Such system equations which are generally adopted for calculating reach-scale river bed evolution have a hyperbolic feature. This fact has implied that upwind schemes to the space derivative of bedload transport in Exner equation are useful numerical methods to avoid bed instabilities in calculating the propagation of a small disturbance. Whereas, a bed diffusion effect which is essentially included in bedload dominated bed evolution has been modelled in equilibrium bedload transport models by considering the local slope effect to the bedload transport. The relation between the numerical and physical diffusion effect to the bed evolution should be investigated to understand the performance and stability of the model. A hyperbolic differential equation controlling the bed evolution was derived from the linearized system equations to understand the numerical characteristic of the propagation of the bed disturbance. We defined a P&eacute;clet number, <i>P_e</i>, as the ratio between the advective effect which controls the propagation of the bed disturbance and the diffusive effect associated with the bed slope effect. The effect of physical diffusion of the bed exceeds the effect of numerical diffusion by the upwind scheme to the bedload transport in the condition which <i>P_e</i> < 2. The series of computations which focus on the propagation of hump type bed disturbance were conducted. The numerical results show that the calculation of propagating the bed disturbance can be physically stable without the upwind scheme when the grid size which satisfies <i>P_e</i> < 2 is used. The grid size which is required such physically stable computation depends on how the bed slope effect is modelled in the bedload transport model.
• AN INFLUENCE OF MODELLING OF SECONDARY FLOWS TO SIMULATION OF FREE BARS IN RIVERS
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 69, 3, 147, 163, 公益社団法人 土木学会, 2013
  Japanese, &nbsp;This paper investigates an influence of the modelling of secondary flows to the formation and development of free bars in rivers by comparing the results of the numerical simulation, the linear stability analysis and the experiments. Free bars which are developed by a physical instability phenomenon between turbulent flow and bed surface of rivers are one of fundamental river morphologies. Theoretical studies by the linear stability analysis have successfully shown that two dimensional morphodynamic models for calculating the river bed evolution can explain the formation of free bars. However, three dimensional flow structures, for instance, secondary flows caused by the meandering flows with increasing the bar height, have also important roles in the dynamics of free bars on a nonlinear level. Although quasi-three dimensional flow models can be a powerful tool to include the three dimensionalities of flows on the framework of two dimensional approaches, the applicability of such models to the dynamics of free bars has not been well verified yet. The results of the linear stability analysis suggested that the model of secondary flows which is assumed under the fully developed stage allows developing the bar with unrealistically high mode. This high mode bar tends to develop under the hydraulic conditions in which the effect of transverse slope for the sediment transport direction is relatively weak. Such instability can be physically suppressed by applying a model of secondary flows which includes the effect of development of secondary flows. The results of numerical simulation shows that proposed model which considers the development of the secondary flows can reasonably reproduce the incipient of free bars which is indicated from the linear stability analysis as well as the equilibrium bar waveheight in the experiments.
• AN EXPERIMENT AND NUMERICAL SIMULATION OF BEDROCK-EROSION CAUSED BY BEDLOAD ON BEDROCK
  OIKAWA Shin; IWASAKI Toshiki; YAMAGUCHI Satomi; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 30, 2, 11, 26, Japan Society of Civil Engineers, 01 Nov. 2012
  English, This paper presents the fundamental studies on the bed degradation process of bedrock induced by the bedload transport over the bedrock. We performed the laboratory experiments focusing on the dependency of the grain size and the strength of bedrock for the erosion velocity of bedrocks. The experimental results show that the grain size and strength of bedrock can affect to the erosion velocity equation of bedrocks. In addition, the movement of the sediment particles over bedrock which has constant side inclining bed was measured to understand the direction of sediment over the bed. We also carried out the numerical simulation of bedrock erosion process by the sediment transport over bedrock to understand the performance of the model proposed by us. The comparison between laboratory experiment and numerical simulation shows that the proposed model overestimates the effect of local slope for sediment transport direction over the bedrocks.
• INSPECTION OF FLOOD CONTROL EFFECT OF BIRDS POINT-NEW MADRID FLOODWAY ON MISSISSIPPI RIVER
  TANAKA Toshiyuki; SHIMIZU Yasuyuki; NELSON Jonathan; IWASAKI Toshiki
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 68, 4, I_1033, I_1038, 公益社団法人 土木学会, 2012
  Japanese, The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States. After the flood in 1927, Mississippi River and Tributaries Project has carried out and changed the engineering policy. One of the biggest projects in MR&T project is the constriction of Birds Point-New Madrid Floodway. In 2011, May, Mississippi River had flooded dramatically and floodway had used which have not been used since 1937. By using floodway smoothly, explosion of levee had executed which was including in Birds Point-New Madrid Floodway operation measure. On our research, we evaluate the effect of the floodway and reproduce the flood by using numerical simulation. By our simulation, floodway has the effect to reduce the water level 1.5m~3m. We also simulate the characteristics of the floodway.
• NUMERICAL SIMULATION ON DEVELOPMENT OF TIDAL CREEK WITH SEEPAGE FLOW
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 68, 4, I_979, I_984, 公益社団法人 土木学会, 2012
  Japanese, This study presents the numerical simulations of initiation and development process of tidal creek network by using two-dimensional morphodynamic model including the seepage flow model, and also discusses the effect of seepage flow for development of tidal creek network. A two dimensional shallow flow equation and two dimensional saturated seepage flow model based on Darcy law were combined to simulate flow field both on and in the bed. The numerical tests with and without seepage flow model were carried out to understand the effect of seepage flow for development of tidal creek in simplified conditions. The result shows that, by including seepage flow model, the channel network tend to become complex one, which has a lot of small scale channels. In addition, the channel width and depth increases by the very shallow flows induced by water supply from inside the bed. This indicates that the seepage flow from inside the bed can have dominant effect for morphodynamics on tidal areas, especially in case of subjecting the dry and wet condition in the bed surface.
• CONSIDERATIONS ON A CALCULATION MODEL FOR A REAL SCALE EXPERIMENT ON FRONT OVERFLOW LEVEE BREACH
  ZENNO Hiroki; IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 68, 4, I_865, I_870, 公益社団法人 土木学会, 2012
  Japanese, It is important from the engineering point of view to predict the collapsing process of river embankment and behavior of overtop flow for reducing disaster during flood. We performed some considerations on refinement of a two-dimensional computational model based on shallow flow equations to predict more accurately the front overflow levee breach phenomena. We tried to introduce a levee erosion model instead of sediment transport model to evaluate the deformation of the levee. In addition, intermittent behavior of the bank collapse is modeled. A calibration of the numerical model is made through the comparison with field experimental data. Recently, a real-scale experiment on a front levee breach was carried out at the Chiyoda Experimental Channel in Hokkaido, Japan. We performed the computation under the same conditions in the experiment. The computational results showed that the present refined model can predict fundamental aspects of the front levee breach phenomena. breach phenomena.
• Numerical simulation on bed evolution and channel migration in rivers
  Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  RIVER FLOW 2012, VOLS 1 AND 2, 673, 679, 2012, [Peer-reviewed]
  English, International conference proceedings
• Computations of real scale experiment on levee breach with a 2D shallow flow model
  Hiroki Zenno; Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  34th IAHR Congress 2011 - Balance and Uncertainty: Water in a Changing World, Incorporating the 33rd Hydrology and Water Resources Symposium and the 10th Conference on Hydraulics in Water Engineering, 491, 498, International Association for Hydro-Environment Engineering and Research (IAHR), 2011
  English, International conference proceedings
• Geomorphological characteristics of female and male-type meanders
  Kozue Tanaka; Yasuyuki Shimizu; Satomi Yamaguchi; Toshiki Iwasaki; Ichiro Kimura; Gaku Tanaka
  7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics(CD-ROM), 7, 1824, 1831, 2011, [Peer-reviewed]
  English, International conference proceedings
• Geometric features of tidal channel networks
  IWASAKI Toshiki; WATANABE Yasunori; OKUDERA Ryota; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 67, 2, 951, 955, 公益社団法人 土木学会, 2011
  Japanese, The complex channel networks have dominant roles for flow, sediment and nutrient transport on salt marshes and tidal flats, and therefore provide rich habitat structures. This study discusses the fundamental geometric properties of tidal channel network by statistical analysis to their channel length and planimetric shapes. We employed channel networks which delineated from experimental and numerical result and also satellite image of real field. It is found that the probability density distribution of channel length can be described by a lognormal distribution, and network in experimental and real scale have similar properties for channel length. The results also indicate that the difference of tidal conditions change the characteristics of tidal channel network configuration.
• HISTORICAL TRANSITION OF RIVER TRAINING WORKS AND INUNDATION CHARACTERISTICS IN SAPPORO
  TANAKA TOSHIYUKI; SHIMIZU YASUYUKI; KIMURA ICHIRO; IWASAKI TOSHIKI
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, I_895, I_900, 公益社団法人 土木学会, 2011
  Japanese, The urbanization in Sapporo was started about only 140 years ago. Before the urbanization, the topography of most part of Sapporo was wetland and not suitable for living and cultivation. Intensive river training works have changed this area dramatically for relatively short period, and made Sapporo as one of the biggest cities in Japan with a population of 1.9 million. In this study, the history of river training works and the transition of inundation characteristics in Sapporo are investigated through old literatures and numerical simulations. First, the historical process of river training constructions was clarified by inspecting old documents and found out some key works. Then numerical simulations of flood were performed in three cases, namely, original topography, after construction of Toyohira-River- Bank and after construction of new Toyohira River Channel. The comparison of simulation results elucidated the relation between river training works and change of inundation behavior.
• EXPERIMENTAL AND NUMERICAL STUDY ON DEVELOPMENT OF TIDAL CREEK NETWORK
  IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, I_859, I_864, 公益社団法人 土木学会, 2011
  Japanese, This paper presents the laboratory tests on developing process of tidal creek network in the small flume and also validation of numerical model which can replicate the morphodynamic evolution of tidal channel and its geomorphic features. The experimental conditions fully satisfied the kinematic, dynamic and sediment transport similarities between the real and experimental scale. The channel network, which has the similar channel characteristics such as ratio between the channel width and depth observed in real field, was reproduced in the experimental flume. This study also conducted the numerical simulations with experimental conditions for validating the physically-based two-dimensional morphodynamic model. The results showed that the proposed morphodynamic model can simulate reasonably the geometry of channel network and its developing process observed in the experiment.
• SIMULATION REAL SCALE EXPERIMENT ON LEVEE BREACH USING 2D SHALLOW FLOW MODEL
  ZENNO Hiroki; IWASAKI Toshiki; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, I_853, I_858, 公益社団法人 土木学会, 2011
  Japanese, Flood in rivers is a common disaster all over the world. If a levee breach happens, it sometimes causes a fatal disaster. In addition, many buildings, urban facilities, lifelines, etc. are seriously damaged. Detailed mechanism of a levee breach has not been clarified yet. Therefore, it is important to predict the collapsing process of riverbank and behavior of overtop flow for reducing damage. We applied a two-dimensional shallow flow computational model to levee breach phenomena caused by overflow and the performance of the model was elucidated. A calibration of the numerical model is made through the comparison with field experimental data. Recently, a real-scale experiment on a levee breach was carried out at the Chiyoda Experimental Channel in Hokkaido, Japan. We performed the computation under the same conditions in the experiment. The computational results showed the excellent performance for simulating levee breach phenomena.
• AN EXPERIMENT AND NUMERICAL SIMULATION OF SLURRY-EROSION CAUSED BY BEDLOAD ON BEDROCK
  OIKAWA Shin; IWASAKI Toshiki; YAMAGUCHI Satomi; SHIMIZU Yasuyuki; KIMURA Ichiro
  Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, I_751, I_756, 公益社団法人 土木学会, 2011
  Japanese, The bed degradation is going rapidly in the upper part of the Ishikari River recently, owing to exposed bedrock erosion caused by bedload on the bedrock. In order to estimate the erosion rate of bedrock, we performed an experiment by a circular channel flume with artificial bedrock made of plaster. We applied the erosion rate estimated by the present experiment to a numerical simulation of bed deformation on the bedrock by using horizontal 2D flow model and the bedload layer model. The result of the simulation shows that gut pattern appeared in the simulated results which is very similar to the experimental result. It was found that the bed degradation was progressed by the erosion caused by sediment transport itself.
• Computations of bed deformation and sediment sorting in meander channel using depth-averaged morphodyamic model
  Toshiki Iwasaki; Yasuyuki Shimizu; Ichiro Kimura
  International Journal of River Basin Management, 9, 3-4, 237, 245, 2011
  English, Scientific journal
• 現地観測と数値解析によるTidal Creekの形成過程に関する考察
  岩崎理樹; 清水康行; 木村一郎; 田中岳
  水工学論文集(CD-ROM), 53, ROMBUNNO.125, Feb. 2009, [Peer-reviewed]
  Japanese, Scientific journal
• SIMULATION OF MORPHOLOGY IN THE TIDAL ENVIRONMENTS
  MASUYA Shigekazu; SHIMIZU Yasuyuki; IWASAKI Toshiki
  PROCEEDINGS OF HYDRAULIC ENGINEERING, 52, 607, 612, 公益社団法人 土木学会, 2008
  This study aims to develop a physically-based morphodynamic model in order to reproduce incision of tidal creek networks as well as evolution of geomorphology in the tidal environments. The process of incision and long-term geomorphologic evolution on tidal flats and marsh is of practical significance from the environmental view point. Generally, it is postulated that tidal creeks are developed as a result of ecomorphologic processes of tidal system driven by tidal energy. Some previous investigations have provided significant insight to this problem. However, there is still lack of a physically-based modeling approach that can replicate the initiation and evolution process of this phenomenon. In this study, physically-based model was applied to a narrow area referred to as tidal flats in order to provide quantitative and qualitative evaluation of its reproducibility. Calculation was conducted for different time scale up to 350 days. Calculation results revealed that the incision of tidal network and its initial development process can satisfactorily be reproduced by a physically-based computational model.
• Numerical simulation of the tidal creek with vegetation growth
  IWASAKI Toshiki; SHIMIZU Yasuyuki
  Journal of applied mechanics, 11, 745, 752, 公益社団法人 土木学会, 2008
  Japanese, In this paper, eco-morphological model is proposed to simulate morphology at tidal environment with vegetation growth. Two numerical experiments such as vegetated scenario and unvegetated scenario were performed to clarify influence of vegetation on morphological evolution. This model was applied to a square tidal flat and calculations were conducted for 350 days. Computational results show that a complicated channel network is formed on tidal marsh and natural levees were appeared around the channel network in both cases. In addition, the vegetation propagated along the natural levees. In vegetated scenario, sediment deposition was enhanced by effect of vegetation on natural levee in comparsion with unvegetated scenario. Therefore, these results indicated that tidal channels are formed more clearly due to vegetation.

• 大規模アンサンブル降雨流出計算データを利用した河道侵食被災リスク評価
  岩崎理樹, 電力土木, 430, 2024
• Modelling long-term equilibrium bar characteristics: A case study of the Chubetsu River
  高橋祐貴; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• Study on morphological evolution of small-sized rivers under climate changes
  大河内駿; 田鍋颯一; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• A study on simple extraction of treetops and their distribution in riparian forests
  宮本豊郎; 奥山瑛人; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• Numerical calculation of morphological evolution of the Jinzu River
  島屋有希; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• Experimental study on the driftwood transport and deposition under the formation of sand bar and braiding channel
  南郁慧; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• Verification of HLL-based river morphodynamic model
  児玉武史; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• Study on the transport materials in rivers: A case study of the Shiribeshitoshibetsu river
  浜山千英; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 80, 2024
• 流路形態が流木の移動,堆積に与える影響に関する実験的検討
  樋口智哉; 南郁慧; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• 河畔林の樹頂点分布に関する現地調査とポイントパターン分析
  宮本豊郎; 奥山瑛人; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• 土砂供給の非平衡性に起因するBedload Sheetの形成と交互砂州動態への影響
  田鍋颯一; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• 豊平川におけるプラスチックごみに関する現地調査
  大屋壱世; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• 流量変動の繰り返しに伴う砂州の形態変化に関する実験的研究
  中根瑞希; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• 洪水時に河川表層を流下する浮遊物の動態把握に関する研究:後志利別川を例として
  浜山千英; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 79th, 2024
• Effects of Graded Sediment Model on the Morphodynamic Calculation of graded sediment bed
  有田圭吾; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 79, 2023
• Field observation of Microplastics in Ishikari and Toyohira Rivers
  大屋壱世; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 79, 2023
• Numerical simulation of advection and dispersion of bedload tracer particles in braided channel
  橋詰竜人; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 79, 2023
• Sensitivity of graded sediment model to the morphodynamic calculaiton of bed and grain size in gravel bed rivers
  有田圭吾; 岩崎理樹, 土木学会全国大会年次学術講演会(Web), 78th, 2023
• The characteristics of morphological changes of riverbed at bed slope and channel width transition point
  田鍋颯一; 岩崎理樹; 清水康行, 土木学会全国大会年次学術講演会(Web), 78th, 2023
• Experiment and Numerical Simulation on Transport Process of Sediment Supplied in River Channel
  平松裕基; 川村里実; 岩崎理樹; 大串弘哉, 寒地土木技術研究, 827, 2022
• Influence of water discharge change due to dam construction on river channel geometry
  高橋祐貴; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 78, 2022
• The flood risk analysis in small streams: A case study of the Pekerebetsu River
  大河内駿; 高橋広大; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 78, 2022
• Comparison of Computational Fluid Dynamics for different grid types
  若原巧実; 清水康行; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 78, 2022
• Field observation of micro-plastics in the Ishikari River
  久保田航平; 岩崎理樹; 清水康行, 土木学会全国大会年次学術講演会(Web), 77th, 2022
• Study on the geometric features of tidal channels in intertidal areas
  伊藤大河; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 77, 2021
• Effects of Bank Strength by Vegetation on Meandering Channel Dynamics
  南郁慧; 久加朋子; 山口里実; 清水康行; 今日出人; 岩崎理樹, 土木学会北海道支部論文報告集(CD-ROM), 77, 2021
• Numerical simulation of upstream-migrating antidunes
  中誠; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 77, 2021
• Effect of variability of multiple hydrographs on the channel deformation
  村上大知; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 77, 2021
• A numerical model of free bar morphodynamics using HLL-type scheme
  岩崎理樹, 数値流体力学シンポジウム講演論文集(CD-ROM), 35th, 2021
• Long term channel process under various patterns of sequential hydrographs
  村上大知; 高橋広大; 清水康行; 岩崎理樹, 数値流体力学シンポジウム講演論文集(CD-ROM), 35th, 2021
• 土砂トレーサーモデルによる着色砂投入実験の再現計算
  山田嵩; 矢部浩規; 岩崎理樹, 土木学会年次学術講演会講演概要集(CD-ROM), 75th, 2020
• 河川におけるプラスチックゴミの移動と堆積に関する調査と実験
  久保田航平; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 76, 2020
• 洪水氾濫に伴う油流出解析モデルの開発
  高橋広大; 岩崎理樹; 井上卓也; 大串浩一郎; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 76, 2020
• 2011年タイ洪水における蒸発散の影響
  宮原望; 岩崎理樹; 清水康行, 土木学会北海道支部論文報告集(CD-ROM), 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, 2020
• 高速流による高水敷侵食に関する水理実験
  岩崎理樹; 井上卓也; 矢部浩規, 土木学会年次学術講演会講演概要集(CD-ROM), 74th, 2019
• 混合砂河床における砂州の数値計算に関する考察
  岩崎理樹, 数値流体力学シンポジウム講演論文集(CD-ROM), 33rd, 2019
• アメリカ地球物理連合秋季大会2017(AGU Fall Meeting 2017)参加報告
  岩崎 理樹; 山崎 秀策, 寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report, 778, 31, 33, Mar. 2018
  土木研究所寒地土木研究所, Japanese
• 三角波による河川管理上のリスク:ブロックの安定性を例として
  岩崎理樹; 井上卓也; 矢部浩規, 国土交通省国土技術研究会(Web), 2018, 2018
• COMPUTATIONS OF THREE-DIMENSIONAL ANTIDUNES IN RIVERS
  岩崎理樹; 井上卓也; 音田慎一郎; 矢部浩規, 土木学会論文集 B1(水工学)(Web), 74, 5, 2018
• NUMERICAL SIMULATION OF BEDLOAD TRACER TRANSPORT BY CONSIDERING VERTICAL TRACER DISPERSION
  濱木道大; 岩崎理樹; 井上卓也; 清水康行, 土木学会論文集 B1(水工学)(Web), 74, 5, 2018
• 2016年アメリカ地球物理連合大会(American Geophysical Union Fall Meeting)と地形学に関する研究集会Gilbert Clubへの参加報告
  岩崎 理樹; 島田 友典; 井上 卓也; 西原 照雅; 水垣 滋, 寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report, 766, 64, 67, Mar. 2017
  土木研究所寒地土木研究所, Japanese
• 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
• MODELING THE THREE-DIMENSIONAL RIVER ANTIDUNES : IMPLICATIONS FOR THE TRIANGLE-SHAPE WATER SURFACE WAVE TRAINS
  岩崎 理樹; 井上 卓也; 矢部 浩規, 水工学論文集 Annual journal of Hydraulic Engineering, JSCE, 61, Ⅰ_901, 906, 2017
  土木学会, Japanese
• 三角状水面波列がブロック安定性に与える影響に関する実験
  岩崎理樹; 井上卓也; 矢部浩規, 土木学会年次学術講演会講演概要集(CD-ROM), 72nd, 2017
• スリランカにおける河川解析ソフトウェア、iRIC講習会の実施とIAHR-APD2016への参加報告
  岩崎 理樹, 寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report, 762, 60, 62, Nov. 2016
  土木研究所寒地土木研究所, Japanese
• 破堤氾濫解析へのiRIC活用事例について
  濱木道大; 山内孝昭; 井上卓也; 清水康行; 岩崎理樹, 土木情報学シンポジウム講演集, 39, 2014
• Numerical Simulations of Forced Bars in Meandering Rivers with Spatial Width Variations
  井上卓也; 岩崎理樹; 清水康行; 伊藤丹, 寒地土木研究所月報, 726, 2013
• 河床における岩盤上の流砂の集中度合に関する実験的検討と数値シミュレーション
  及川森; 岩崎理樹; 山口里実; 清水康行; 井上卓也, 水工学論文集(CD-ROM), 56, 2012

• 水資源管理工学特論, 2024年, 修士課程, 工学院
• 水資源管理工学特論, 2024年, 博士後期課程, 工学院
• 物理学Ⅰ, 2024年, 学士課程, 全学教育
• 防災工学演習, 2024年, 学士課程, 工学部
• 水理学Ⅱ, 2024年, 学士課程, 工学部
• Computational Continuum Mechanics, 2024年, 学士課程, 工学部
• 応用数学Ⅰ, 2024年, 学士課程, 工学部
• 水理学演習Ⅱ, 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

• American geophysical union
• JAPAN SOCIETY OF CIVIL ENGINEERS

• ブルーインフラ機能を持つ河川流動護岸の開発
  科学研究費助成事業
  Jun. 2025 - Mar. 2028
  風間 聡; 小野 桂介; 岩崎 理樹
  日本学術振興会, 挑戦的研究(萌芽), 東北大学, 25K22105
• 機械学習と力学モデルの融合による流域スケール流木予測管理技術の構築
  科学研究費助成事業
  Apr. 2024 - Mar. 2028
  木村 一郎; 磯部公一; 岩崎理樹
  日本学術振興会, 基盤研究(B), 富山大学, 24K00985
• 急流河川における降雨パターンを考慮した樹林化動態解明と流路変動・侵食リスクの検討
  科学研究費助成事業
  01 Apr. 2023 - 31 Mar. 2027
  久加 朋子; 山野井 一輝; 川村 里実; 岩崎 理樹
  日本学術振興会, 基盤研究(B), 富山県立大学, 23K26213
• 侵食・洗掘による破堤危険度評価からのバックキャスト的アプローチによる礫床河川の河床変動解析・構造物変状解析の高度化と信頼性評価
  河川基金助成事業 河道研究プロジェクト
  Oct. 2024 - Mar. 2027
  戸田祐嗣; 岩崎理樹; 西口浩司; 周月霞
  公益財団法人 河川財団, Coinvestigator
• 急流河川における降雨パターンを考慮した樹林化動態解明と流路変動・侵食リスクの検討
  科学研究費助成事業
  Apr. 2023 - Mar. 2027
  久加 朋子; 山野井 一輝; 川村 里実; 岩崎 理樹
  日本学術振興会, 基盤研究(B), 富山県立大学, 23H01519
• 流れ－河床変動過程における内的・外的不確実性を踏まえた河道被災ポテンシャル評価
  科学研究費助成事業
  01 Apr. 2023 - 31 Mar. 2026
  岩崎 理樹; 山田 朋人
  北海道十勝川水系ペケレベツ川を対象とし，d4PDF降雨データを力学的ダウンスケーリングした詳細降雨分布計算結果に対して流出計算を実施し整理されている多数の年最大イベントのハイドログラフ群をk-shapeクラスタリングによって分類し，特徴的なハイドログラフ形状について検討した．その結果，ハイドログラフは大まかに最大ピーク前後に第2のピークを持つかか，また最大ピークと第二ピーク間の時間が離れているか，で5つに分類できることを示した．同様の解析をより規模の大きな河川である同水系の音更川へ適用したところ，概ね同様の波形特性で分類できることを確認したが，音更川のほうが流量波形のばらつきがより大きく，流域規模によって流量の不確実性は異なることが示唆された．
  
  
  このように分類されたハイドログラフがどのような河床変動を引き起こすかについて，iRIC-Nays2DHによる計算を実施した．平成28年9月豪雨時の流量と同一のピーク流量を有するハイドログラフを各クラスターより抽出し，これらを上流端境界条件とした河床変動計算を実施することで，河床・河岸侵食に及ぼす流量波形の影響について定量的に評価した．その結果，流量波形に応じて河岸侵食量に違いがあり，特に最大ピークよりも前に第二ピークがあるハイドログラフでは，前半のピークによって河岸侵食が進行することで河道内に土砂堆積を引き起こすため，最大ピーク時にはその河床上昇によって流路が変動しやすく，側岸侵食が大きくなりえることが明らかとなった．
  
  
  上記のような河床変動に及ぼす外的不確実性影響とは別に，流砂モデルが持つ内的不確実性の影響を評価するために，蛇行流路における混合砂河床を対象とした室内実験結果に対して，流砂モデルや遮蔽効果，また代表粒径の取り方などを変化させた河床変動計算を行い，再現性に対する各種流砂モデル要素が及ぼす影響について検討した．
  日本学術振興会, 基盤研究(C), 北海道大学, 23K04038
• 河床変動解析における不確実性評価と現場への適用に関する技術検討
  河川砂防技術研究開発 河川技術・流域管理分野（指定課題）
  May 2024 - Mar. 2026
  岩崎理樹; 泉典洋; 戸田祐嗣; 溝口敦子
  国土交通省, 河床変動解析における不確実性評価と現場への適用に関する技術検討
• 局所・流域スケールの視点に基づく洪水時橋梁被害リスク評価の展開
  科学研究費助成事業 基盤研究(A)
  05 Apr. 2021 - 31 Mar. 2025
  二瓶 泰雄; 渡邉 健治; 川尻 峻三; 岩崎 理樹; 柏田 仁
  日本学術振興会, 基盤研究(A), 東京理科大学, 21H04577
• 気候変動後の流量発生分布を考慮した砂州の波高増大・固定化リスクの評価手法の提案
  河川砂防技術研究開発 河川技術・流域管理分野（地域課題）
  Apr. 2022 - Mar. 2024
  国土交通省, Coinvestigator
• 河川におけるプラスチックごみに関する量的・ 質的特性の解明
  河川基金助成事業
  Apr. 2022 - Mar. 2023
  公益財団法人 河川財団, Principal investigator, 2022-5211-001
• Vulnerability assessment of water and sediment-related disasters by using large-scale water, sediment transport, and morphodynamic model
  Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists
  Apr. 2020 - Mar. 2023
  岩崎 理樹
  今後予期される気候変動を踏まえた河道の脆弱性を評価するために，北海道を対象とした大量サンサンブル降雨―流出計算データを解析し，移動床計算に重要と考えられるハイドログラフパターンについて，K-shapeクラスタリング手法により検討した．これにより，数百という多数の流量データから，重要と考えられる十数の流量ハイドログラフのパターンとして特徴化することが可能となった．クラスタリングから得られた代表ハイドログラフを移動床計算の境界条件として用い，河床－河岸侵食に関しても起こりうる可能性をより網羅的な外力条件から評価可能な手法について開発できた．
  上記，短期的河道脆弱性評価に使用可能な1洪水データに加えて，より中長期的な河道脆弱性を検討するために，アンサンブルメンバーごとの連続流量ハイドログラフを確率水文統計し，長期的に起こりうる条件をより網羅的に検討した．急流河川を対象とした移動床計算の結果，現在気候条件においては平均的な外力条件において，比較的堤防内で流路変動が収まる状態であっても，気候変動後の条件においては，最小流量シナリオにおいても，堤防が高い割合で流路変動に伴う侵食の影響を受けることを明らかにした．
  昨年度検討した給砂条件の影響について，代表的な沖積河道地形の一つである交互砂州へ与える影響を二次元移動床計算から検討した．その結果，給砂条件の違いが下流に与える影響は比較的給砂条件を変化させた境界付近に強く表れる一方で，その領域より下流に形成される交互砂州へ与える影響は小さいことが明らかとなった．
  高精度で安定的な移動床計算を実現するための計算スキームとして，近似リーマン解法の一つであるHLL系のスキームを浅水流モデルと河床変動モデルを合わせたシステム方程式に適用したモデルを構築し，自由砂州の実験結果と比較することでその精度について検証した．
  Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, 20K14831
• 大量アンサンブル降雨―流出計算データを利用した流路変動解析による河道被災リスクの定量評価手法の構築
  河川砂防技術研究開発 河川技術部門
  May 2020 - Mar. 2022
  岩崎理樹,清水康行,泉典洋,今日出人,山田朋人,久加朋子,星野剛,山口里実,井上卓也
  国土交通省水管理・国土保全局
• 浮体混在型河川災害の予測・減災モデルの構築とiRICへの実装
  Apr. 2020 - Mar. 2022
  北海道河川財団, Coinvestigator
• 混濁流による高流砂階のベッドフォームの堆積構造解明と堆積モデルの構築
  科学技術研究費補助金 基盤研究（B）
  Apr. 2018 - Mar. 2021
  横川美和
  文部科学省, Competitive research funding
• Comprehensive study on wide-area disasters due to typhoon no.19 and 21 in 2019
  Grants-in-Aid for Scientific Research Grant-in-Aid for Special Purposes
  Dec. 2019 - Mar. 2020
  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
  令和元年東日本台風（台風19号）とその2週間後の大雨（台風21号と低気圧）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，多角的・総合的に多くの分野の専門家からなる研究グループを結成し，調査研究を継続して行った．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つのテーマと主に対象とした．その結果，台風19号による豪雨に，山岳部は勿論，平野部でもseeder-feeder機構が貢献していることを，XRAINによる立体観測情報，ひまわりによる観測情報により，seeder-feeder機構を表現した数値モデルを用いて示した．2019年台風19号による豪雨発生機構について，気象庁メソ客観解析データを用いて，降水活動に係る大気安定度や水蒸気場の解析をし，本豪雨発生時には，最近の他の豪雨事例と比較して，湿潤絶対不安定が持続して形成されていたことが分かった．また，洪水氾濫による建築被害に関しては，長野市内の水害被害住宅を対象に，復旧後の室内環境に着目して現地調査を実施している．復旧には数ヶ月の期間を要するが，復旧手順は現地の判断で実施している場合が多く，客観的な情報が整備されていない．その一助となるべく，限られた事例ではあるが，復旧手順とともにそれに伴う環境改善効果を評価しながら知見を蓄積し，環境改善を測るために室内の浮遊真菌濃度や部位の含水率等を計測した．さらに，風水害に関しては，台風に伴って発生した竜巻の影響が大きかったため，台風と竜巻発生の関係を過去の気象資料から抽出し整理した．
  Japan Society for the Promotion of Science, Grant-in-Aid for Special Purposes, Tokyo University of Science, 19K24678
• 土砂トレーサーを利用した土砂動態－地形変動過程の理解と予測
  科学技術研究費補助金 若手研究
  Apr. 2017 - Mar. 2020
  岩崎理樹
  文部科学省, Principal investigator, Competitive research funding
• 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
• 感潮域における持続可能な環境保全手法の確立に向けた地形変動予測モデルの開発
  科学技術研究費補助金 特別研究員奨励費
  Apr. 2010 - Mar. 2013
  岩崎理樹
  [1]水路網の形成・発達に及ぼす主要因を抽出する目的で,潮汐周期,振幅,領域長などのパラメータを変化させた異なる水理条件下における実験を行い,水路網形成に対する水理パラメータ依存性について検討した.水路網の形成・発達を定性的に評価することで,その形成過程に関する考察を行うと共に,Horton則による水路網形状定量化手法により,水路数といった水路網の形状特性に関する検討を行った.得られた結論を以下に列挙する.1)潮汐による流れが強いほど,水路網が形成されづらい一方,相対的に流れが弱い場合は細かな水路が発達し,一水路網が複雑となることが示唆された.2)水路化には侵食と堆積の両方が重要であるが,両者の物理メカニズムは異なる可能性がある.3)位数1の水路の確率密度分布形状より,位数1の水路の長さスケールは潮汐周期が長くなるほど小さくなる傾向にある.また,時間の経過と共に確率密度分布はその形状を変化させる.
  [2]異なる水理条件の下で実施された室内実験により得られる水路網形状の相違を生み出す要因について簡易的な数学モデルを用いて考察を行った.一定勾配である単純地形及び規則的な潮汐を想定し,この条件における流れ一地形変動を簡易に表現可能な数学的モデルを構築した,このモデルから地形変動を表す方程式が移流拡散型の方程式を導出し,この方程式から導出される移流拡散度合いの比を表すパラメータ,ペクレ数を定義した.このペクレ数を各実験ケースで求めて結果と比較し,以下の結論を得た.1)岸沖方向のペクレ数が大きい場合,水路が直線する一方,小さい実験では水路が蛇行する傾向が見られた.2)横断方向の移流拡散の度合いを表すパラメータが小さい領域では,水路網が形成されず,大きい領域では複雑な水路網が形成される傾向がある.これは,横断方向の拡散の影響が強い場合,不安定な成分である水路が拡散するためと考えられる.
  文部科学省, 特別研究員奨励費, 北海道大学, Principal investigator, Competitive research funding, 10J02689