Proposing index method of three dimensional water catchment area and peak discharge estimating method for debris flow scale prediction

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04706
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Kyoto University
• Principal Investigator: Nakatani Kana 京都大学, 防災研究所, 教授 (80613801)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 土石流 / 集水領域 / 規模推定 / GIS / 数値シミュレーション

Outline of Final Research Achievements

This study proposes a new water catchment area index that takes into account water storage within a mountain body and water movement across basins to predict the scale of debris flows, and aims to clarify the factors that affect the scale of debris flows. We conducted surveys and experiments, focused on topographical and geological differences, conducted data organization, GIS analysis, and applied simulations on debris flows. In addition to the two-dimensional basin, the topographical index that represents the scale of debris flows well is the volume of a mountain body takes into account the three-dimensional basin. And we considered the water catchment area includes a wide range of mountain bodies that takes into account adjacent mountain streams shown to be able to express the water volume needed to consist the real debris flows. We proposed an analysis method to express the peak discharge of debris flows, and investigated various parameters setting to express debris flow scale.

Free Research Field

砂防学

Academic Significance and Societal Importance of the Research Achievements

土石流災害を軽減するためには、規模予測を精確に行うことが求められる。従来、土石流規模を示す指標に二次元的な流域面積が用いられる。しかし、発生した土石流の土砂量や、土石流として挙動するのに必要な降雨由来の水の量が、流域面積では十分表現されなかった。広島県内の土石流事例を対象として、調査やGIS分析、シミュレーションにより検討して、流域を三次元化した山体の体積を用いることで土砂量をベースとした土石流規模が表現されること、隣接流域を含む広い山体で水の量を検討すると、必要な水の量が表現されることを明らかにした。更に土石流の流量ピークを推定する解析手法を提案して、防災に貢献する知見を得た。