Researcher Profile and Settings

Master

Affiliation (Master)

• Research Faculty of Agriculture　Fundamental AgriScience Research　Forest Science

Affiliation (Master)

• Research Faculty of Agriculture　Fundamental AgriScience Research　Forest Science

researchmap

Profile and Settings

Profile and Settings

• Name (Japanese)

  Kasai

• Name (Kana)

  Mio

• Name

  201301080904879880

Achievement

Research Interests

• open cracks   connectivity   catchment scale sediment delivery   landslide susceptibility map   surface roughness   GIS analysis   landslide activity   セデイメントバジェット   mountain stream   bedform   Sediment wave   

Research Areas

• Other / Other

Research Experience

• 2024/04 - Today The University of Tokyo Center for Spatial Information Science at the University of Tokyo
• 2024/04 - Today Hokkaido University Graduate School of Agriculture Research Faculty of Agriculture Professor
• 2016/07 - 2024/03 The University of Tokyo Center for Spatial Information Science
• 2010/09 - 2024/03 Hokkaido University
• 2009/08 - 2010/08 Landcare Research Soils and Landscapes Visiting Scientist
• 2006/07 - 2009/06 （独）土木研究所 研究員
• 2005/10 - 2005/12 CSIRO Land and Water Rivers and Coasts Visiting Scientist
• 2000/02 - 2001/02 Macquarie University Division of Environmental and Life Sciences Visiting Associate
• 1997 - 1999 Kyushu University School of Agriculture

Education

• 2001/03 - 2005/09  Macquarie University  Division of Environmental and Life Sciences  Department of Physical Geography
•        -   Kyushu University  School of Agriculture

Published Papers

• A new index representative of seismic cracks to assess post-seismic landslide susceptibility

  Shui Yamaguchi, Mio Kasai

  Transactions in GIS (26) 1040 - 1061 2022/01 [Refereed]
  
• Estimation of the behavior of coarse woody debris in an intense storm in August 2016 and its budget for the Tottabetsu River Catchment, Eastern Hokkaido

  Takuya KUDO, Norihiro NAGANO, Akira MATSUOKA, Tomoya HAYAKAWA, Takanori KAMIJO, Yohei MATSUYAMA, Nobutomo OSANAI, Mio KASAI

  Journal of the Japan Society of Erosion Control Engineering 73 (6) 3 - 11 2021/03 [Refereed]
  
• Incorporating ground cracks in the estimation of post-seismic landslide susceptibility

  Shui Yamaguchi, Mio Kasai

  Proceedings of GEOMORPHOMETRY 2020 Conference 166 - 169 2020/08 [Refereed][Not invited]
   

  ISBN 978 88 8080 282 2
• October 2019 Sediment Disaster in the Tohoku Region owing to Typhoon No. 19 (Tyhpoon Hagibis)

  Michiya IRASAWA, Takashi KOI, Ching-Ying TSOU, Nobuaki KATO, Shinjiro MATSUO, Mizuho ARAI, Masahiro KAIBORI, Takashi YAMADA, Mio KASAI, Taeko WAKAHARA, Daisuke HIGAKI, Hajime IKEDA, Yoshiharu ISHIKAWA, Kenichi ARAI, Shinji HIROSE, Tatsuya SATO, Hideki KAWATABATA, Manabu KOUBU, Satoshi NIWA, Kazuhiro SUGAWARA, Hiroyuki MATSUSAKA, Nobuyuki TADA

  International Journal of Erosion Control Engineering 13 (2) 48 - 55 2020/05/22 [Not refereed][Not invited]
  
• Landslide susceptibility maps produced by WOE and Logistic regression methods for Nachi River Basin, Wakayama Prefecture, Japan

  Kazuki YANAI, Mio KASAI

  Journal of the Japan Landslide Society 57 (3) 90 - 98 1348-3986 2020 [Refereed][Not invited]
  
• Sediment disasters caused by Typhoon Hagibis on October, 2019 in Tohoku region

  Michiya IRASAWA, Shinjiro MATSUO, Mizuho ARAI, Masahiro KAIBORI, Ching-Ying TSOU, Takashi YAMADA, Mio KASAI, Koi TAKASHI, Nobuaki KATO, Taeko WAKAHARA, Daisuke HIGAKI, Hajime IKEDA, Yoshiharu ISHIKAWA, Kenichi ARAI, Shinji HIROSE, Tatsuya SATO, Hideki KAWATABATA, Manabu KOUBU, Satoshi NIWA, Kazuhiro SUGAWARA, Hiroyuki MATSUSAKA, Nobuyuki TADA, Toshiyuki KON

  Japan Society of Erosion Control Engineering 72 (6) 42 - 53 0286-8385 2020 [Refereed][Not invited]
  
• Actual situation of forests after the Taisho mudflow in the Biei River; Tokachi Mountain, Hokkaido

  Kim, J, Asano, H, Honma, H, Ikegami, T, Yamada, T, Kasai, M, Nanri, T, Marutani, T

  Journal of the Japan Society of Erosion Control Engineering 72 (3) 4 - 10 0286-8385 2019/09 [Refereed][Not invited]
  
• Topographic effects on frequency–size distribution of landslides triggered by the Hokkaido Eastern Iburi Earthquake in 2018

  Mio Kasai, Takashi Yamada

  Earth, Planets and Space 71 2019/08 [Refereed][Not invited]
  
• Identification of active landslide blocks with optimized hotspot analysis using surface roughness index

  Mio Kasai

  Journal of the Japan Landslide Society 56 (3) 15 - 23 2019/05 [Refereed][Not invited]
  
• Sediment production in catchment scale from specific sedimentation of dam reservoirs in Hokkaido, Japan

  Tomomi Marutani, Mikio Kuroki, Mio Kasai

  Chikei/Transactions, Japanese Geomorphological Union 40 (1) 93 - 104 0389-1755 2019/01/01 

  Specific amount of sediment deposition in dam reservoirs is a useful index to appraise the degree of sediment production from the catchments. We examined the relationships between the amount and geomorphic and geological characters of catchments of various sizes in Hokkaido, Japan, by analyzing annual sedimentation records in 105 reservoirs. The 28 of the reservoirs were situated in mountainous areas, and the annual specific sediment yield from the catchments was 178m 3 /km 3 /year on average. Sediment yield from the catchments underlain by sedimentary rocks was 8 times larger than those underlain by volcanic rocks, and rainfall pattern was strongly reflected in the sedimentation record. On the other hand, specific sediment yield rates became more dependent on dam utilization by human activities for larger catchments. The data revealed that annual specific sediment yield increased with the size in catchments smaller than 100 km2, while the relationship is reversed for those larger than the size.
• Sediment-related disasters induced by the 2018 Hokkaido Eastern Iburi Earthquake

  OSANAI Nobutomo, FUJINAMI Takeshi, MURAKAMI Yasuhiro, INAMI Yu, SATO Hajime, NAKATA Yasutaka, ABE Tomoyuki, OHNO Hiroyuki, TAKESHI Toshiya, TANAKA Toshiaki, ONODA Satoshi, KAIBORI Masahiro, HONMA Hiroki, YANAI Kazuki, MIYAZAKI Tomoyoshi, UENO Junya, HAYAKAWA Tomoya, SUGAI Kouhei, YAMADA Takashi, KASAI Mio, HAYASHI Shin-ichiro, KATSURA Shin'ya, FURUICHI Takahisa, YANAI Seiji, TAKEBAYASHI Hiroshi

  Journal of the Japan Society of Erosion Control Engineering 公益社団法人 砂防学会 71 (5) 54 - 65 0286-8385 2019 [Refereed][Not invited]
   

  On 6^th September 2018, a large earthquake (the 2018 Hokkaido Eastern Iburi Earthquake) with the magnitude of 6.7 struck the eastern Iburi region, Hokkaido and triggered numerous landslides. The landslides were distributed densely over hilly areas (400 km²) in Atsuma, Abira, and Mukawa Town, the total area of which reached 13.4 km². All landslides were shallow landslides except a large-scale deep-seated one generated in midstream area of the Hidaka-Horonai River. The area is covered by thick pyroclastic fall deposits derived from the Tarumae Volcano etc., and the strong seismic shock triggered shallow landsliding of them. Some shallow landslides occurred at a relatively gentle slope (<15°). Shallow landslides moving along a valley topography tended to travel longer than those moving along a non-valley topography. In catchments where shallow landslides densely occurred, the ratio of landslide area to the total catchment area was very large compared with past earthquake events, suggesting that the catchments became highly devastated. Based on these survey results, we propose viewpoints for preventing secondary disasters in the damaged area and for promoting countermeasures against and studies on earthquake-induced landslide disasters in volcanic regions.

• 北海道のダム堆砂速度から見た流域スケールでの土砂生産量の変化

  丸谷知己, 黒木幹男, 笠井美青

  地形 40 (1) 93 - 104 2019 [Refereed][Not invited]
  
• Channel evolution controlled by valley configuration during 70 years in a severely erosive catchment: Mangaoporo River, New Zealand

  Kasai, M, Aoki, D, Peacock, D, Maturani, T

  Catena 174C 324 - 338 2019 [Refereed][Not invited]
  
• 周氷河性斜面の崩壊・侵食に起因する大規模な土砂移動の実態－2016年台風10号による北海道ペケレベツ川を例に－

  宮崎知与, 澤田雅代, 松岡直基, 立川義通, 高嶋繁則, 吉田安範, 林真一郎, 古市剛久, 笠井美青, 小山内信智

  砂防学会誌 71 (2) 22 - 33 2018 [Refereed][Not invited]
  
• A Method for Estimating Maximum Damage Caused by Sediment Disaster by Surveying with Artificial Satellite SAR Imagery

  Shin-ichiro HAYASHI, Shin?ya KATSURA, Mio KASAI, Nobutomo OSANAI, Takashi YAMADA, Tomomi MARUTANI, Tomoyuki NORO, Joko KAMIYAMA

  Interpraevent Band 1 401 - 407 2018 [Refereed][Not invited]
  
• A Study on Criteria of Warning and Evacuation for Large-scale Sediment Disasters Considering the Relationships with Sediment Movement and Damage

  Yuna SUZUKI, Shin-ichiro HAYASHI, Shinya KATSURA, Mio KASAI, Nobutomo OSANAI, Tomomi MARUTANI

  Interpraevent Band 1 387 - 393 2018 [Refereed][Not invited]
  
• The Effects of Hydraulic Structures on Streams Prone to Bank Erosion in an Intense Flood Event: A Case Study from Eastern Hokkaido

  Daisuke AOKI, Mio KASAI, Mari IGURA

  Interpraevent Band 1 270 - 275 2018 [Refereed][Not invited]
  
• Grain Size Distribution of the 1926 Volcanic Mudflow at Mt. Tokachi, Japan

  Tomoyuki NANRI, Takashi YAMADA, Mio KASAI, Tomomi MARUTANI, Shigenori TAKASHIMA, Takayuki YAMAHIRO

  Interpraevent Band 1 163 - 169 2018 [Refereed][Not invited]
  
• Geologic and Topographic Features of Slope Failure Sites in the Aso Caldera Wall Inducted by the 2016 Kumamoto Earthquake

  Haruka SAITOU, Shinya KATSURA, Ryota UMETANI, Mio KASAI, Tomomi MARUTANI

  Interpraevent Band 1 117 - 122 2018 [Refereed][Not invited]
  
• 阿蘇カルデラ壁で発生した山腹崩壊に伴う土砂と流木の到達範囲とそれに基づく危険区域設定の提案

  清水収, 児玉龍朋, 笠井美青

  砂防学会誌 70 (5) 3 - 14 2018 [Refereed][Not invited]
  
• Sediment discharge in the Tokachi region, Hokkaido, caused by Typhoon No. 10 (Lionrock), 2016

  小山内 信智, 笠井 美青, 林 真一郎, 桂 真也, 古市 剛久, 伊倉 万理, 高坂 宗昭, 藤浪 武史, 水垣 滋, 阿部 孝章, 布川 雅典, 吉井 厚志, 紅葉 克也, 渡邊 康玄, 塩野 康浩, 宮崎 知与, 澤田 雅代, 早川 智也, 松岡 暁, 佐伯 哲朗, 稲葉 千秋, 永田 直己, 松岡 直基, 井上 涼子

  新砂防 = Journal of the Japan Society of Erosion Control Engineering : 砂防学会誌 砂防学会 69 (6) 80 - 91 0286-8385 2017/03 [Refereed][Not invited]
   

  災害報告
• 被害が広域に及ぶ大規模な土砂災害に対する調査技術の活用事例に基づく定量的分析

  林真一郎, 内田太郎, 桂真也, 笠井美青, 小山内信智, 丸谷知己

  日本地すべり学会誌 54 (2) 18 - 25 2017/03 [Refereed][Not invited]
  
• Disaster map of the Taisho volcanic mudflow informing the arrival time and the level of damage after the eruption of Mt. Tokachi in 1926

  NANRI Tomoyuki, YAMADA Takashi, KASAI Mio, MARUTANI Tomomi

  Journal of the Japan Society of Erosion Control Engineering 公益社団法人 砂防学会 69 (1) 12 - 19 0286-8385 2016 [Refereed][Not invited]
   

  In 1926 a volcanic mudflow triggered by the eruption of Mt. Tokachi, named "Taisho mudflow", ran through the Furano River in Hokkaido and caused destructive damage along the course. Several disaster maps presenting the path have been produced since then, while additional information of the arrival time and the levels of damage on the map was considered helpful to establish evacuation plans for the future eruption. In this study, the travelling time of the flow was estimated by interviewing locals who experienced the disaster (Nanri et al., 2004). The damage level was also classified into three groups, High (Ⅰ) : 90% of houses were completely destroyed and 30% of residents were killed, Moderate (Ⅱ) : 30-90% of houses were completely destroyed and 10-30% of residents were killed, and Low (Ⅲ) : houses were partly destroyed and less than 10% of residents were killed. Estimating fluid dynamic force produced by the flow, more than 10³ KN/m for the level Ⅰ, 10²-10³ KN/m for the level Ⅱ, and 10¹-10² KN/m for the level Ⅲ were required during the travel respectively. Applying the relationship between average river bed slope and the force given, the distribution of the damage level was estimated and demonstrated through the path. In summary, it took the flow 20 minutes to travel from the crater through the valley to 0.5 km downstream of the outlet after the eruption, giving a high level of damage. Subsequently, another 10 minutes were required to travel over a flood plain as damaging the area to a moderate degree. Finally, after 40 minutes from the eruption the flow arrived at the Kami-Furano Township, as yielding a low degree of damage.

• パイプハイドロフォンの音響波形に及ぼす境界条件の影響

  後藤健, 伊藤隆郭, 長山孝彦, 笠井美青, 丸谷知己

  砂防学会誌 68 (4) 3 - 11 2015 [Refereed][Not invited]
  
• Tectonic and volcanic forcing on fluvial systems: two case studies from Japan

  Parkner, T, Kasai, M

  Past Global Changes Magazine 22 (1) 36 - 37 2014 [Not refereed][Not invited]
  
• Experimental and theoretical tools for estimating bedload transport using a Japanese pipe hydrophone

  Goto, K, Itoh, T, Nagayama, T, Kasai, M

  International Journal of Erosion Control Engineering Japan Society of Erosion Control Engineering 7 (4) 101 - 110 1882-6547 2014 [Refereed][Not invited]
   

  A Japanese pipe hydrophone is an acoustic sensor that is widely used in Japan to measure bedload transport. Here we report experimental and theoretical tools for calculating bedload transport using a Japanese pipe hydrophone, and discuss the limitations based on laboratory tests. We found a linear relationship between the momentum of colliding particles and the maximum amplitude of the acoustic wave, and found that the grain size can be calculated using this linear relationship. We determined the range over which this linear relationship holds, and found that it depended on the amplifier gain; we then used it to calculate the maximum flow depth. The median frequency and the form of the frequency distribution of the acoustic wave depended on the grain size, slightly on the flow discharge. The bedload transport rate can be calaculated using the velocity of the bedload and the sediment volume in the bedload layer using the linear relationship between the momentum of the colliding particles and the maximum amplitude of the acoustic wave.
• Laboratory experiments in relation to the slope erosion process using coarse volcaniclastic materials

  SANO Chihiro, NUNOKAWA Masanori, KASAI Mio, MARUTANI Tomomi

  Boreal Forest Research 北方森林学会 61 (0) 129 - 131 2186-7526 2013 [Refereed][Not invited]
  
• レーザー測量データを用いた岩盤クリープ斜面の表面形状把握

  横山修, 内田太郎, 中野陽子, 石塚忠範, 笠井美青, 鈴木隆司

  砂防学会誌 64 (6) 13 - 24 2012/03 [Refereed][Not invited]
  
• Patterns of Sediment Flux Determined from Dendrochronological Analysis of Debris Fans within Headwater Catchments, Hokkaido, Japan

  KIMURA Takashi, KASAI Mio, EBISU Nobuhiro, MARUTANI Tomomi

  Transactions, Japanese Geomorphological Union 日本地形学連合 33 (1) 61 - 81 0389-1755 2012/01/25 [Refereed][Not invited]
   

  This study examines the pattern of episodic sediment yield and relationship to catchment morphology within 13 steep and credible headwater catchments in the Hidaka Mountain Range, Hokkaido. The history of episodic sediment yield of each catchment was dendrochronogically reconstructed from the sequence of sediment accumulated on debris fans at catchment outlets. The timing of fan growth was then compared with landslide distributions and rainfall records for the past 40 years, to determine the connectivity between slope and channel processes as well as the sensitivity of catchments for episod...
• The Role of LiDAR Data on Evaluation of Shallow Landslide Susceptibility and Detection of Mass-rock Creeping Slope

  UCHIDA Taro, NAKANO Youko, AKIYAMA Koichi, TAMURA Keiji, KASAI Mio, SUZUKI Ryuji

  Transactions,Japanese Geomorphological Union 日本地形学連合 31 (4) 383 - 402 0389-1755 2010 [Refereed][Not invited]
   

  In the last decade, a variety of studies examined applicability of high-resolution topographic data developed by LiDAR data for prediction and clarification of sediment movement, including debris flow, shallow landslide, deep-seated landslide and so on. Here we examine (1) usefulness for prediction of shallow landslide location using simple physically based model and (2) effectiveness for identifying mass-rock creeping slopes based on the characteristic eigenvalue ratio and slope angle. We analyzed the data of the shallow landslides at Hiroshima, Japan and showed high-resolution topographic data was useful for prediction of shallow landslide location. We also confirmed effectiveness for identifying mass-rock creeping slopes based on the analysis of the data of Waniduka Mt., Miyazaki, Japan.
• Experiments of insertion type borehole inclinometer to standardize measurement methods

  CHIBA Shinichi, FUJISAWA Kazunori, KASAI Mio, SUGITA Osamu, SATO Narimasa, SUGANUMA Takeshi

  Landslides The Japan Landslide Society 47 (1) 60 - 65 1348-3986 2010 [Refereed][Not invited]
  
• LiDAR-derived DEM evaluation of deep-seated landslides in a steep and rocky region of Japan

  Mio Kasai, Manabu Ikeda, Toshihiro Asahina, Kazunori Fujisawa

  GEOMORPHOLOGY 113 (1-2) 57 - 69 0169-555X 2009/12 [Refereed][Not invited]
   

  In steep and rocky terrains, their rough surfaces make it difficult to create landslide inventories even with detailed maps/images produced from airborne LiDAR data. To provide objective clues in locating deep-seated landslides, the surface textures of a 5 km(2) steepland area in Japan was investigated using the eigenvalue ratio and slope filters calculated from a very high resolution LiDAR-derived DEM. The range of filter values was determined for each of a number of surface features mapped in the field and these included: cracked bedrock outcrops, coarse colluvial deposits, gently undulating surfaces, and smooth surfaces. Recently active slides commonly contained patches of ground in which deposition and erosion occurred together near the erosion front, or where cracked bedrock outcrops and coarse colluvial deposits coexisted under a gently undulating surface. The characteristic eigenvalue and slope filter values representing this sliding process were applied to maps of the DEM derived filter values to extract potential sites of recent landslide activity. In addition, the relationships between the filter values of deep-seated landslides at various stages of evolution within the field mapped area were extended to the entire study area, to assess the contribution that landslide evolution makes to change in the landscape as a whole. While landslide components made up the steepest as well as the gentlest parts of the landscape depending on their evolutionary stage, landslides were constantly coarsened and steepened by progressive erosion, probably initiated by river bank erosion at the foot of slopes. (C) 2009 Elsevier B.V. All rights reserved.
• 土地利用変化が山地流域の土砂生産・輸送プロセスに与えた影響 ―ニュージーランド，ウェラマイア川流域―

  笠井 美青

  砂防学会誌 公益社団法人 砂防学会 61 (3) 3 - 4 0286-8385 2008
• 航空レーザー測量データから作成されたＤＥＭの解析に基づく地すべり地形発達プロセスの推定

  笠井美青, 池田学, 藤澤和範, 松田昌之, 鈴木雄介

  日本地すべり学会誌 45 (2) 118 - 124 2008 [Refereed][Not invited]
  
• Buffers, barriers and blankets: The (dis)connectivity of catchment-scale sediment cascades

  Kirstie A. Fryirs, Gary J. Brierley, Nicholas J. Preston, Mio Kasai

  CATENA 70 (1) 49 - 67 0341-8162 2007/06 [Refereed][Not invited]
   

  Catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency. This paper introduces the concept of landform impediments, termed buffers, bangers and blankets, that impede sediment conveyance by limiting the connectivity between landscape compartments. Buffers restrict sediment delivery to channels, barriers inhibit sediment movement along channels, and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment. These features operate as a series of switches which turn on/off processes of sediment delivery, determining the effective catchment area at any given time. Using previously documented examples, the role of these features in affecting the operation of sediment cascades in a low relief, passive landscape setting such as the Australian landmass is contrasted to examples from high relief, uplifting settings in New Zealand. The Australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since European settlement have impacted upon landscape sensitivity and prospects for river recovery. This approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting. (C) 2006 Elsevier B.V. All rights reserved.
• Channel processes following land use changes in a degrading steep headwater stream in North Island, New Zealand

  Mio Kasai

  GEOMORPHOLOGY 81 (3-4) 421 - 439 0169-555X 2006/11 [Refereed][Not invited]
   

  In headwater streams in steep land settings, narrow and steep valley floors provide closely coupled relationships between geomorphic components including hillslopes, tributary fans, and channel reaches. These relationships together with small catchment sizes result in episodic changes to the amount of stored sediment in channels. Major sediment inputs follow high magnitude events. Subsequent exponential losses via removal of material can be represented by a relaxation curve. The influence of hillslope and tributary processes on relaxation curves, and that of altered coupling relations between components, were investigated along a 1.3 km reach of a degrading channel in the 4.8 km(2) Weraamaia Catchment, New Zealand. Extensive deforestation in the late 19th and early 20th centuries, followed by invasion of scrubs and reforestation, induced changes to major erosion types from gully complexes to shallow landslides. Changes in the size and pattern of sediment slugs from 1938 to 2002 were analysed from air photographs tied to detailed field measurement. The rate and calibre of sediment flux changed progressively following substantive hillslope input in a storm in 1938. Subsequently, the channel narrowed and incised, decoupling tributary fans from the main stem, thereby scaling down the size of sediment slugs. As a consequence, the dominant influence on the behaviour of sediment slugs and associated relaxation processes, changed from tributary fans to the type and distribution of bedrock outcrops along the reach. (c) 2006 Elsevier B.V. All rights reserved.
• Impacts of land use change on patterns of sediment flux in Weraamaia catchment, New Zealand

  M Kasai, GJ Brierley, MJ Page, T Marutani, NA Trustrum

  CATENA 64 (1) 27 - 60 0341-8162 2005/11 [Refereed][Not invited]
   

  Forest clearance between the 1890s and the early 1920s, subsequent scrub growth, and commencement of an afforestation program in 1979, modified the pattern and rate of sediment delivery to valley floors via shallow landslides and gully complexes in a steep headwater catchment (4.8 km(2)) in New Zealand. Analysis of the historical record, air photograph interpretation, and field survey indicates that both erosion types occurred across the catchment in the 1938 storm, aggrading channel beds and widening the active channel zone. In contrast, a I in 100 year event in 1988 (Cyclone Bola) induced numerous shallow landslides,,but erosion of gully complexes was largely restricted to subcatchments that retained pasture, and the geomorphic impact of this event on channels was small. The changing volume and calibre of materials delivered to the valley floor, and the distribution of gully complexes, altered patterns and rates of channel adjustment after the events, and de resulting sediment flux. Development of gully complexes maintained coupling processes with channels for periods up to 102 years, forming wide channels in downstream reaches. Upstream-dowmtream connectivity along the trunk stream was altered by the formation of a large debris fan at the confluence with a tributary subjected to gully complex erosion. In contrast, slopes subjected to shallow landslides became decoupled from channels within 10 years, accelerating channel degradation and narrowing. Effective conveyance of a large volume of fine-grained materials promoted immediate aggradation of gentle-gradient channels downstream. As gully complex areas stabilized following an increase in forest and scrub cover, channel courses became significant sediment sources. Although shallow landslide activity will continue to induce intermittent aggradation in the future, it is inferred that average sediment yield will continue to diminish to levels approaching those experienced prior to clearcutting, and the pattern of sediment flux will recover by 2030. (c) 2005 Elsevier B.V. All rights reserved.
• Channel bed adjustments following major aggradation in a steep headwater setting: findings from Oyabu Creek, Kyushu, Japan

  M Kasai, T Marutani, G Brierley

  GEOMORPHOLOGY 62 (3-4) 199 - 215 0169-555X 2004/10 [Refereed][Not invited]
   

  A typhoon in 1993 induced major aggradation along Oyabu Creek, a steep, gravel bed mountain stream in Kyushu, Japan. Processes of sediment reworking are inferred from a 7-year monitoring program that measured adjustments to channel cross-sections, the longitudinal profile, and the extent/distribution of bedrock outcrops along a 3-km study reach. Over time, the reach adopted a riffle and pool structure, with notable increase in the area of exposed bedrock on the bed. This adjustment process was characterised by progressive reduction in sediment storage change per unit flow. The relaxation pathway following disturbance induced by the typhoon was shaped by the magnitude and frequency of subsequent rainfall events, the capacity of these events to transport available sediments, and physical linkages between reaches. Adjacent subreaches demonstrated differing relaxation pathways in response to these influences, induced by spatial and temporal variability in threshold conditions along the channel. Longer-term evidence indicates that responses to major disturbance, such as the 1993 typhoon, occur as 'cycles' of around 20-year duration. A relaxation period of 7 years is required to attain a quasi-equilibrium bed configuration and rate of sediment flux. The timeframe of cycles is considered to reflect changes to hillslope-channel bed coupling, marking the period required to generate sufficient sediment stores to reactivate phases of aggradation and subsequent degradation. (C) 2004 Elsevier B.V. All rights reserved.
• Patterns of sediment slug translation and dispersion following typhoon-induced disturbance, Oyabu Creek, Kyushu, Japan

  M Kasai, T Marutani, GJ Brierley

  EARTH SURFACE PROCESSES AND LANDFORMS 29 (1) 59 - 76 0197-9337 2004/01 [Refereed][Not invited]
   

  A six-year monitoring programme characterized the migration/dispersion patterns of sediment slugs generated following typhoon-induced disturbances in 1993 and 1997 along a single-thread gravel-bed stream, Oyabu Creek, on Kyushu Island, Japan. This laterally confined creek comprises riffle-pool sequences with intervening bedrock outcrops. The passage of sediment pulses associated with sediment slug processes reflected, and was controlled by, the riffle-pool structures which provided channel bed roughness, the volume of sediment stored along valley floors, and the distribution of bedrock outcrops. Changes to bed material size following major sediment inputs during the disturbance events also exerted an influence on subsequent sediment slug processes. The sequence of rainfall events, together with changes to channel bed structure, induced different phases in the sediment slug processes. The capacity of a reach to store or trap sediment, as recorded by the longitudinal structure of the channel, varied during these differing phases. Copyright (C) 2004 John Wiley Sons, Ltd.
• Rainfall influence on sediment yielded from small and steep catchments : Kyushu mountain region, Japan, using simple sampling tanks

  KIM Hoon, MARUTANI Tomomi, KASAI Mio

  砂防学会誌 : 新砂防 = Journal of the Japan Society of Erosion Control Engineering 砂防学会 55 (5) 11 - 21 0286-8385 2003/01/15 [Refereed][Not invited]
  
• THE INVESTIGATION INTO THE LAND CONDITION OF KASEGAWA DAM RESERVOIR BASIN BY USING THE REMOTE-SENSING DATA AND THE ESTIMATE OF ITS SEDIMENT YIELD VOLUME

  HASHIMOTO Haruyuki, WATANABE Katsutoshi, JUN Byungdug, UENO Kenji, YAMANAKA Minoru, KASAI Mio, NOGAMI Shouji, OGATA Tsutomu

  PROCEEDINGS OF HYDRAULIC ENGINEERING 公益社団法人 土木学会 45 (45) 805 - 810 0916-7374 2001 [Refereed][Not invited]
   

  It is important to estimate sediment yield volume accurately in reservoir basins in the planning of the dam-construction. In the present study we select Kasegawa dam under construction in Saga Prefecture as a case study area. We first investigate the land surface condition and vegetation activity in the reservoir basin by using rcmotc-sensing data. Secondly we examine sediment grain size distribution in the rivers in the reservoir basin. On the basis of these results and sediment transport mechanics we finally estimate the sediment yield volume from the reservoir basin.
• Estimation of temporally averaged sediment delivery ratio using aggradational terraces in headwater catchments of the Waipaoa River, North Island, New Zealand

  M Kasai, T Marutani, LM Reid, NA Trustrum

  EARTH SURFACE PROCESSES AND LANDFORMS 26 (1) 1 - 16 0197-9337 2001/01 [Refereed][Not invited]
   

  The sediment delivery ratio was estimated for two periods (28 years and eight years) following reforestation of seven tributary catchments (0.33 to 0.49 km(2)) in the headwaters of the Waipaoa River basin, North Island, New Zealand. In these catchments, gully erosion, which largely resulted from clearance of the natural forest between 1880 and 1920, is the main source of sediment to streams. Reforestation commenced in the early 1960s in an attempt to stabilize hillslopes and reduce sediment supply. Efforts have been partially successful and channels are now degrading, though gully erosion continues to supply sediment at accelerated rates in parts of the catchment. Data from the area indicate that the sediment delivery ratio (SDR) can be estimated as a function of two variables, psi (the product of catchment area and channel slope) and A, (the temporally averaged gully area for the period). Sediment input from gullies was determined from a well defined relationship between sediment yield and gully area. Sediment scoured from channels was estimated from dated terrace remnants and the current channel bed. Terrace remnants represent aggradation during major floods. This technique provides estimates of SDR averaged over periods between large magnitude terrace-forming events and with the present channel bed. The technique averages out short-term variability in sediment flux. Comparison of gully area and sediment transport between two periods (1960-1988 and 1988-1996) indicates that the annual rate of sediment yield from gullies for the later period has decreased by 77 per cent, sediment scouring in channels has increased by 124 per cent, and sediment delivered from catchments has decreased by 78 per cent. However, average SDR for the tributaries was found to be not significantly different between these periods. This may reflect the small number of catchments examined. It is also due to the fact that the volume of sediment scoured from channels was very small relative to that produced by gullies. According to the equation for SDR determined for the Waipaoa headwaters, SDR increases with increasing catchment area in the case where A, and channel slope are fixed. This is because the amount of sediment produced from a channel by scouring increases with increasing catchment area. However, this relationship does not hold for the main stem of the study catchments, because sediment delivered from its tributaries still continues to accumulate in the channel. Higher order channels are, in effect, at a different stage in the aggradation/degradation cycle and it will take some time until a main channel reflects the effects of reforestation and its bed adjusts to net degradation. Results demonstrate significant differences among even low order catchments, and such differences will need to be taken into consideration when using SDR to estimate sediment yields. Copyright (C) 2001 John Wiley & Sons, Ltd.
• Sediment volume yielded from small mountainous catchments eroded by landsides

  MARUTANI Tomomi, KASAI Mio, MAKITA Masayo

  砂防学会誌 : 新砂防 = Journal of the Japan Society of Erosion Control Engineering 砂防学会 52 (6) 24 - 31 0286-8385 2000/03/15 [Refereed][Not invited]
   

  Because sediment input volume from branch to main stream is the key knowledge for estimating input-output balance of sediment budget along river channel, this study was focused on the temporal changes in sediment volume supplied from small catchments. Sediment volume was monitored in the concrete sand-pocket(4m×2m×1m)set at the mouth of four small catchments. Each catchment is the area between 2.48 and 10.14 ha and channel slopes of them between 0.093 and 0.249. Sediment volume measurement was conducted at 17 times during three years. The influence of catchment area, such as channel slope, landslide area and its occurrence years, on sediment volume supplied from each catchment was examined. The proportion of the duration rainfall against the duration sediment volume at each measuring period, sediment supply rate, yields regression line as a exponential curve except for the periods of less rainfall in winter season. This indicates that the sediment supply rate defined as the duration sediment volume per the duration rainfall is applied to any periods, for example, several days or a year. Since the annual sediment supply rate, V_y, decreases according to years after landslide occurrence year, T, the relationship between both is represented as V_y=α⋅exp(-γ⋅T). Here landslide area was likely to response to landslide occurrence as the initial condition, α. Catchment area, relief and averaged channel slope were not likely to influences on decreasing of annual sediment supply rate, γin such small catchments.
• Sediment generation from numerous shallow landslides related with clear cutting at granite mountain, Mt.Ichifusa, Japan.

  Marutani, T, Kasai, M, Ebisu, N, Trustrum, N.A

  Interpraevent Band 1 271 - 279 2000 [Refereed][Not invited]
  
• 水系を通じた土砂流出速度の推定--ニュージーランドワイパオア川における事例

  丸谷 知己, 笠井 美青, Reid Leslie M

  水資源研究センタ-研究報告 京都大学防災研究所付属水資源研究センタ- (20) 101 - 111 0285-4872 2000 [Not refereed][Not invited]
  
• Influence of storm-related sediment storage on the sediment delivery from tributary catchments in the upper Waipaoa River, New Zealand

  T Marutani, M Kasai, LM Reid, NA Trustrum

  EARTH SURFACE PROCESSES AND LANDFORMS 24 (10) 881 - 896 0197-9337 1999/09 [Refereed][Not invited]
   

  Although much is known about overall sediment delivery ratios for catchments as components of sediment production and sediment yield, little is known about the component of temporary sediment storage. Sediment delivery ratios focused on the influence of storm-related sediment storage are measured at Matakonekone and Oil Springs tributaries of the Waipaoa River basin, east coast of New Zealand. The terrace deposits of both tributaries show abundant evidence of storm-related sedimentation, especially sediment delivered from Cyclone Bola, a 50 year return rainfall event which occurred in 1988. The sediment delivery ratio is calculated by dividing the volume of sediment transported from a tributary to the main stream by the volume of sediment generated at erosion sites in the tributary catchment. Because the sediment delivery volume is unknown, it can be calculated as the difference between sediment generation volume and sediment storage volume in the channel reach of the tributary. The volume of sediment generated from erosion sites in each tributary catchment was calculated from measurements made on aerial photographs dating from 1960(1:44 000) and 1988 (1 :27 000). The volume of sediment stored in the tributary can be calculated from measurements of cross-sections located along the tributary channel, which are accompanied by terrace deposits dated by counting annual growth rings of trees on terrace surfaces. Sediment delivery ratios are 0.93 for both Matakonekone catchment and Oil Springs catchment. Results indicate that Oil Springs catchment has contributed more than twice the volume of sediment to the Waipaoa River than the Matakonekone catchment (2.75 x 10(6) m(3) vs 1.22 x 10(6) m(3)). Although large volumes of sediment are initially deposited during floods, subsequent smaller flows scour away much of these deposits. The sediment scouring rate from storage is 1.25 x 10(4) m(3) a(-1) for Matakonekone stream and 0.83 x 10(4) m(3) a(-1) for Oil Springs stream. Matakonekone and Oil Springs channels respond to extreme storms by instantaneously aggrading, then gradually excavating the temporarily stored sediment. Results from Matakonekone and Oil Springs streams suggest a mechanism by which event recurrence interval can strongly influence the magnitude of a geomorphic change. Matakonekone stream with its higher stream power is expected to excavate sediment deposits more rapidly and allow more rapid re-establishment of storage capacity. Copyright (C) 1999 John Wiley & Sons, Ltd.
• 一次谷源頭部の地表変動攪乱の空間分布

  伊藤 哲, 丸谷知己, 笠井美青

  日本林学会九州支部研究論文集 51 123 - 124 1998/06 [Refereed][Not invited]
  
• Sediment Storage at Confluence Points along a Mountainous Stream

  KASAI Mio, MARUTANI Tomomi

  砂防学会誌 : 新砂防 = Journal of the Japan Society of Erosion Control Engineering 砂防学会 49 (6) 17 - 23 0286-8385 1997/03/15 [Refereed][Not invited]
   

  The morphology of confluence points along mountanious streams is affected by geomorphological characteristics of tributaries, such as catchment size and channel slope. These characteristics also influence the way in which sediment is transported through channels and the volume of sediment supplied to confluence points. This is demonstrated at the Oyabu creek in the Kyushu mountain range, based on 2-years of field observations. The results were as follows.
  (1) At the Oyabu creek, sediment yielded from tributaries accumulated at the confluence points of relatively small steep tributaries, and was transported to the lower reach of confluence points in the case of large gentle tributaries.
  (2) Changes in sediment volume depended on the preceding volume of sediment in storage, irrespective of tributaries characteristics.
  (3) Volumes of sediment yielded from tributaries increased with increasing catchment size.
• 市房山崩壊地群

  丸谷 知己, 井倉 洋二, 笠井 美青

  砂防学会誌 : 新砂防 = Journal of the Japan Society of Erosion Control Engineering 砂防学会 49 (2) 69 - 72 0286-8385 1996/07/15 [Refereed][Not invited]
  
• River bed deformation at confluence points in a mountainous stream

  Marutani, T, Kasai, M

  Interpraevent Band 1 283 - 292 1996 [Refereed][Not invited]
  
• Geomorphological Analysis fo the Oyabu River Basin

  MARUTANI T, KASAI M

  Bulletin of the Kyushu University Forest 九州大学 72 (0) 117 - 124 0453-0284 1995/03 [Refereed][Not invited]
  
• Spatial Change of the Strength of Woody Debris Accompanied with Sediment Storage

  MARUTANI Tomomi, KASAI Mio

  新砂防 砂防学会 47 (6) 3 - 7 0286-8385 1995/03/01 [Refereed][Not invited]
  
• Sediment storage by woody debris on a stream bed of a mountainous river channel

  KASAI Mio, MARUTANI Tomomi

  Journal of the Japanese Forestry Society 一般社団法人日本森林学会 76 (6) 560 - 568 0021-485X 1994/11/01 [Refereed][Not invited]
   

  Sediment storage is often caused by woody debris on stream beds of mountainous river channels. Woody debris is produced by land slips of mountain slopes that build up a wall structures on stream beds (called a "wall" here). The volume of sediment storage seems to relate to the strength of a wall which consists of many logs. The purpose of this paper is to clarify the relationship between the volume of sediment storage and the strength of a wall according to the wall structure changes along the distance from the log source. Strength of a wall, S, was calculated as the product of cross-point ...

MISC

• A disaster experience as an opportunity to enhance environmental education : Sediment and flooding disaster in August 2016 in the western Tokachi catchment, Hokkaido, Japan

  古市剛久, 小山内信智, 林真一郎, 笠井美青, 桂真也  宮城教育大学環境教育研究紀要  19-  25  -32  2017/03  [Not refereed][Not invited]
  
• Airborne LiDAR and SAR survey by an unmanned helicopter : Jozankei area,Sapporo

  KASAI Mio  Journal of the Japan Society of Erosion Control Engineering  67-  (3)  67  -71  2014  [Not refereed][Invited]
  
• 連続する複断面化床固工の土砂調節機能に関する実験的研究~石狩川水系砂金沢を事例に~

  五十嵐和秀, 笠井美青, 丸谷知己  砂防学会研究発表会概要集  2011-  2011
• 土地利用変化が山地流域の土砂生産・輸送プロセスに与えた影響 ―ニュージーランド, ウェラマイア川流域－

  笠井美青  砂防学会誌  61-  (3)  58  -63  2008  [Not refereed][Invited]
  
• Particle size distribution and sediment mobility in branch cannels of the Waiapu Catchment, New Zealand(Papers Presented at the Spring Meeting of the Union, May, 2003)

  MIYAMOTO Akira, MARUTANI Tomomi, KASAI Mio  地形  24-  (3)  324  -324  2003
• Effect of Geomorphological Factors of Small Catchments on Peak Discharge at Confluence Points

  Kasai Mio, Fujino Takako, Marutani Tomomi  Journal of the Faculty of Agriculture, Kyushu University  39-  (3)  221  -227  1995/03  

  Effect of geomorphological factors of small branch catchments on the peak discharge of a main channel at confluence points was analyzed from the observation of discharge and the measurement of geomorphology. Catchment area, catchment shape, channel gradient, bifurcation ratio and length ratio of branch catchments were acquired from 1/25000 topographical map. A hydrograph appeared during a flood changed according to the catchment shape, represented by the bifurcation ratio and the length ratio. The effect of the channel gradient on the discharge was little in small catchments (from 0.859 km^2 to 0.945 km² in area). A sum of peak values of discharge of branch catchments equaled to a peak value of discharge in main channel. Peaks in the hydrography curve of branch catchments often coincided to those of main channel. In the case that confluence points departed about 300 m in distance, the peaks disappeared in the hydrography curve.
• Pyroclastic flow sedimentation thickness and gully - erosion in Unzen Fugendake. ( Ministry of Education S ).

  丸谷知己, 笠井美青, 芳賀弘和, 川西良仙  雲仙岳の土石流・火砕流災害に関する総合的研究 No.06302079 平成7年  39  -42  1995  [Not refereed][Not invited]
  

Books etc

• Understanding and Reducing Landslide Disaster Risk Vol.2

  Mio Kasai (OthersCan repeat LiDAR surveys locate future massive landslides?)
  Springer 2021/01 (ISBN: 9783030602277) 504 81-85 

  Kasai M. (2021) Can Repeat LiDAR Surveys Locate Future Massive Landslides?. In: Guzzetti F., Mihalić Arbanas S., Reichenbach P., Sassa K., Bobrowsky P.T., Takara K. (eds) Understanding and Reducing Landslide Disaster Risk. WLF 2020. ICL Contribution to Landslide Disaster Risk Reduction. Springer, Cham. https://doi.org/10.1007/978-3-030-60227-7_7
• Landslides induced by the 2018 Hokkaido Eastern Iburi Earthquake

  「地震による地すべり災害」刊行委員会 (Contributor3.7 Topographic effects on frequency-size distribution of landslides)
  北海道大学出版会 2020/09 (ISBN: 9784832982352) x, 355p
• 砂防学

  笠井美青 (Contributor地形解析)
  朝倉書店 2019/04
• Gravel Bed Rivers 6

  Page, M, Marden, M, Kasai, M, Gomez, B, Peacock, D, Betts, H, Parkner, T, Marutani, T, Trustrum, N (ContributorChanges in basin-scale sediment supply and transfer in a rapidly transformed New Zealand landscape)
  Elsevier 2007
• 流域学事典―人間による川と大地の変貌―

  笠井美青 (Contributor「柔岩地帯の河川」「土砂流出の規模と頻度」「土砂収支」「セディメントウェーブ」)
  北大図書刊行会 2006

Presentations

• ルーマニアのマスムーブメントに関する国際共同研究

  小口高, 早川裕弌, 笠井美青, 河本大地, 飯塚浩太郎, Lucian Dragut, Mihai Micu

  日本地形学連合2022年秋季大会  2022/11
• Assessment of post-seismic landslide susceptibility using an index representative of seismic cracks

  Mio Kasai, Shui Yamaguchi

  EGU General Assembly 2022  2022/05
• 地震亀裂に着目した2016年熊本地震後の崩壊危険度評価

  山口柊生, 笠井美青

  令和４年度砂防学会研究発表会（宮崎 オンライン）  2022/05
• UAV-LiDARとUAVマルチスペクトルセンサを用いた地すべり活動の把握

  野口絹子, 笠井美青, 早川裕弌, 飯塚浩太郎, 小口高

  日本地形学連合秋季大会  2021/12
• Can repeat LiDAR surveys locate future massive landslides?

  Mio Kasai

  World Landslide Forum 5  2021/11
• A new index representative of seismic cracks to assess post-seismic landslide susceptibility  [Invited]

  Mio Kasai, Shui Yamaguchi

  Italy-Japan joint workshop on landslide monitoring systems and related topics  2021/11
• 2016年熊本地震後の崩壊危険度評価

  山口柊生, 笠井美青

  第60回地すべり学会研究発表会  2021/09
• 北海道胆振東部地震で発生した地すべり斜面における地震前の地形的特徴

  武井健太, 笠井美青

  第60回 日本地すべり学会研究発表会  2021/09
• Incorporating ground cracks in the estimation of post-seismic landslide susceptibility

  Shui Yamaguchi, Mio Kasai

  Geomorphometry 2021  2021/09
• ALBとドローン空撮による戸蔦別川における河床変動観測

  岸本海笛, 笠井美青, 佐野寿聰

  鵡川・沙流川流域土砂動態現地勉強会(第11回)  2021/08
• 亀裂を考慮した地震後の崩壊危険度評価

  山口柊生, 笠井美青

  日本地球惑星科学連合2021年大会  2021/06
• ALBとドローン空撮による、北海道東部戸蔦別川における河床低下プロセスの観測

  岸本海笛, 笠井美青, 佐野寿聰

  日本地球惑星科学連合2021年大会  2021/06  オンライン
• 平成28年8月北海道豪雨時の戸蔦別川における河畔林流失と河床剪断力

  法覚俊, 笠井美青, 山田孝

  砂防学会研究発表会概要集(Web)  2020
• 北海道十勝川水系における平成28年8月出水での河道変化

  青木大輔, 笠井美青, 山田孝

  砂防学会研究発表会概要集(Web)  2019
• 流域サイズと出水時の発生流木量の関係

  法覚俊, 笠井美青, 山田孝

  砂防学会研究発表会概要集(Web)  2019
• 北海道における土砂災害リスクの特徴

  小山内信智, 林真一郎, 古市剛久, 山田孝, 笠井美青, 桂真也

  砂防学会研究発表会概要集(Web)  2019
• Flume experiment on the contribution of snowmelt induced by the various composition of pyroclastic debris and hot water to lahar discharge

  鈴木貴大, 山田孝, 笠井美青

  雪氷研究大会講演要旨集(Web)  2018
• 砂防・治山の国際的な貢献に向けて-ニュージーランドとの学術交流・共同研究-

  丸谷知己, 笠井美青, 山田孝

  砂防学会研究発表会概要集  2015
• 土石流によって流出した大径木の木造家屋への衝突-2014年8月20日の広島県広島市安佐南区での事例-

  吉留慧, 山田孝, 笠井美青, 野呂智之

  砂防学会研究発表会概要集  2015
• 流木を含んだ土石流の衝突荷重測定実験

  野坂隆幸, 笠井美青, 丸谷知己, 山田孝

  砂防学会研究発表会概要集  2015
• Particle size distribution and sediment mobility in branch cannels of the Waiapu Catchment, New Zealand(Papers Presented at the Spring Meeting of the Union, May, 2003)  [Not invited]

  MIYAMOTO Akira, MARUTANI Tomomi, KASAI Mio

  Transactions, Japanese Geomorphological Union  2003/07

Association Memberships

• Asia Oceania Geosciences Society   American Geophysical Union   European Geosciences Union   JAPAN GEOSCIENCE UNION   JAPANESE GEOMORPHOLOGICAL UNION   THE JAPAN LANDSLIDE SOCIETY   JAPAN SOCIETY OF EROSION CONTROL ENGINEERING   

Research Projects

• Mass movements and sediment disasters in Romania: integrated understanding from physical and social approaches

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2021/10 -2026/03 

  Author : 小口 高, 笠井 美青, 河本 大地, 早川 裕弌, 飯塚 浩太郎

   

  本研究はルーマニアでの現地調査を主体とし、2022年3月に最初の調査を行う予定であった。しかし、コロナ禍により不可能となった。そこで、次年度以降の本格的な研究に向けて日本で可能な検討を進めた。 土砂移動と土砂災害の重要な原因である斜面崩壊について、中解像度のデータを用いた統計的な検討を行った。調査地域は本研究の対象であるルーマニア中部のカルパチア山脈と、日本の南アルプス南部である。斜面崩壊の発生しやすさを地形・地質などの土地条件から推定するモデルを、機械学習の技法であるランダムフォレスト法を用いて構築した。この際には実際に斜面崩壊が発生した場所とともに、斜面崩壊がない場所をサンプリングする必要があるが、後者については多様な方法が提案されている。ここでは複数の種類のランダムサンプリングを適用し、モデルの適合度を地域の地質の複雑さを考慮しつつ検討した。その結果、地質が複雑な地域ではランダムサンプリングの方法が適合度を大きく変えることが判明した。この地質の重要性を示す結果は、現地で高解像度のデータを取得して行う次年度以降の検討に示唆を与えるものである。他にも本研究と関連する地形学的な研究を行い、たとえば地震で生じる斜面崩壊や地すべりに対し、線状凹地の発生が強く関与していることを統計解析や機械学習で明らかにした。 本研究では現地調査でドローンを活用する予定である。そのための技術的な検討として、地形・植生の3次元モデルの構築と、それに基づく変化の抽出の位置精度について研究した。また、衛星データを用いて広域の地形変化を抽出する手法についても検討した。 さらに、土砂災害と関連するルーマニアの社会経済・文化的事情等に関する文献のレビューも行った。また、研究対象地域が属するブザウ地域がユネスコ世界ジオパークに認定されたことを受けて、ジオパークとしての本地域の状況についても調査した。
• Prediction methods of sediment discharge areas due to slope failures caused by earthquake in volcanic ash deposited areas

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2019/04 -2022/03 

  Author : YAMADA TAKASHI

   

  Machine learning was conducted on the slope failures that occurred in Atsuma due to the 2018 Hokkaido Iburi East Earthquake, using pre- and post-earthquake LP data, which revealed that slopes with cracks appearing on the ground in advance were vulnerable and at high risk of slope failure. In addition, groundwater analysis was conducted to reproduce the moisture condition inside the slope at the time of the earthquake. The results suggest that the water retention property of the slip surface and the permeability of the layer below the slip surface are the key points to focus on when identifying slopes in danger of failure. Furthermore, we developed a method to establish a two-dimensional spreading and deposition area for a block sliding surface failure by calculating the reach of the collapsed soil using a rigid body sliding model (the dynamic friction coefficient was measured using field sediment samples) and giving the average value of the collapse width in the transverse direction.
• Mechanism of multiple hazard chains and adaptations for rapidly population decline in Japan

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2018/04 -2021/03 

  Author : 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.
• Comprehensive study on the 2018 Hokkaido Eastern Iburi Earthquake and its disaster

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2018/10 -2019/03 

  Author : Takahashi Hiroaki

   

  Comprehensive investigation on the 2018 Hokkaido Eastern Iburi earthquake and its disaster was conducted. Mainshock rupture initiated at deepest part and major slip was occurred in 20-30km deep. Multiple simultaneous landslides in Atsuma town was induced by combination of strong ground shaking and weak sliding layer between pyroclastic fall deposit layers. Halloysite cray minerals was discovered in all sliding layers. Simulation suggested landslides might attack residential houses within 6 seconds. Observed peak ground motions in nearby area were larger than common distance attenuation model. Severe wooden house damage in Mukawa town was due to amplified seismic waves due to site effects. Sounding and boring investigation revealed filled low-density volcanic ash and higher groundwater level in liquefaction area. Electricity blackout caused severe damage in social and economic activities of Hokkaido. These scientific outcomes were explained to residents at public briefing session.
• Debris flow mitigation with water absorption

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2014/04 -2016/03 

  Author : MARUTANI Tomomi, KASAI Mio

   

  Aiming to debris flow mitigation, we examined water absorption form debris flow and decrease in velocity and impact force using flume experiments. The experimental flume was made by 5m long horizontal acrylic panels and debris pool at the top of the flume. As results of experiments with water absorbent, approximately 2.3 times decreasing in water content of debris flow reduce the velocity to one-half and the impact force to one-eighths. The experiments with the screen dam model has successfully shown the same results. The field survey for finding the issues of countermeasure was conducted at the screen dam site of Nojiri-river, Sakurajima. There are still issue removing the debris accumulation on the dam site.
• Comparative study on discontinuous nature of sediment transfers and changes of watershed management in river systems

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 1998 -2001 

  Author : MAITA Hideji, SHIMIZU Osamu, MARUTANI Tomomi, KUROKI Mikio, MIYAZAKI Toshitaka

   

  We conducted the drainage net analysis to examine the Horton's laws in Japanese basins. As a result, it is suggested that channel classification based on the stream order is effective to compare the characteristics of sediment transport between rivers in a basin level because the classification could represent regularities of channel form and the regional characteristics regarding sediment transport. We also analyzed sediment distributions along the river course in objective basins using the theory of stable channel by Kuroki. As a result, it is suggested that the variation from stable channel forms could represent the characteristics of sediment transport in rivers. Furthermore We examined the adjustment of unstable sediment stored in a mountainous bedrock channel of the upper Hitotsuse River, Kyushu, the bed-material transport estimated from channel morphodynamics of the Sorachi River, Hokkaido, the geomorphological properties and the time series movement of sediment yield in*the upper area of the Tenryu River, central Japan, and the sediment budget and sediment yield due to shallow landslides in the upper River Oi, central Japan. As a result, it is suggested that sediment storage in channels is most important to understand discontinuous nature of sediment transfers, and also the distribution of stored sediment in a drainage system and its changes by flood events are important to understand the dynamics of sediment transport in a basin level. Furthermore it is important to identify whether a channel is in supply limited condition or in transport limited condition because the imbalance between the stream power and sediment availability causes sediment storage.
• Disturbance and recovery of riparian and fresh water ecosystem caused by sediment transport associated with flood events

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 1997 -1999 

  Author : MARUTANI Tomomi, INOHARA Youji, OKANO Tetsuo, OGAWA Shigeru, KASAI Mio, TERAKA Yukio

   

  Based on three years observation for morphological riverbed changes and sediment transport, the factors disturbing riparian and freshwater ecosystems were analyzed. Rainfall, runoff, sediment storage volume, sediment production volume, bank erosion rate, suspended sediment volume and rock size distribution along the drainage net were measured at the Oyabu creek of a headwater of the Hitotsuse River located in the middle mountain range of Kyushu island, Japan. The following results were gained. (1) Sediment accumulated after a flood event trended to restore sediment storage volume to the minimum value (4000mィイD13ィエD1/km) with time elapse. (2) Sediment slug associated with riverbed degradations was occurred with 2.65m/day in velocity and that with riverbed aggradations was occurred with 4.6m/day in velocity respectively. (3) The volume of sediment supply from tributary channels decreased exponentially against time elapse. (4) Rock size distribution along a channel related with macroscopically the distance from sediment production source, and slope and catchment area of significant tributaries (slope<0.15, area>10ha) joined with main channel. (5) Bank erosion rate of the upper channel (8m in averaged channel width) of the Oyabu creek was 10cm/year. These results imply that the recovery of riparian and freshwater ecosystems is likely to be controlled by magnitude of riverbed aggradation, frequency of flooring as the recurrence interval and the time lapse after flood event. Furthermore rock size distribution along drainage net can influence on the relaxation time of ecological property of fresh water.