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Development of a numerical propagation model for debris flow and flood flow considering flow blockages by large boulders and woody debris and its application for spatial assessment on damage risks

考虑大石块和木质碎片堵塞的泥石流和洪水流数值传播模型的开发及其在损害风险空间评估中的应用

基本信息

批准号：
22K14454
负责人：
和田孝志
金额：
$ 2.91万
依托单位：
Tottori University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Early-Career Scientists
财政年份：
2022
资助国家：
日本
起止时间：
2022-04-01 至 2025-03-31
项目状态：
未结题

项目摘要

本研究では，市街地内の土石流・洪水流複合氾濫対策に資するため，複数の土石流・洪水流を同一時間軸で解析し，かつ，道路狭窄部・橋梁部での大礫・流木閉塞を予測可能な数値計算モデルを開発するとともに，開発モデルの解析結果から，市街地内の人工物配置による土石流閉塞や氾濫範囲変化の発現可能性，すなわち土石流被災リスク偏在性に関する評価手法の確立を目指すものである．令和４年度は，当初計画で予定していた「谷筋勾配変化に伴う粒度偏析・流木偏析変化モデルの構築」に向けて，谷筋勾配変化が土石流の大小砂礫の輸送・偏析に及ぼす影響を把握するための水路実験を行った．上下区間で２種類の勾配を設定可能な変勾配水路を用い，勾配変化点下流区間の複数の計測点で土石流先頭部の輸送土砂濃度，流動深，大粒子砂礫存在割合，大小砂礫の輸送速度を計測し，これらの水理量の縦断的な遷移傾向を把握し，さらに，勾配変化に対する土石流の性状変化過程の指標化を行った．この結果，土石流規模や土石流構成物平均径に対する勾配変化に伴う性状変化の推移傾向を複数パターンに分類できる可能性が確認された．さらに，次年度実施予定の「市街地内の土石流被災リスク偏在性評価手法の検討」に先立って，山地・河川が隣接する密集市街地において，本川・支川洪水氾濫や土石流流入といった複合氾濫条件下での氾濫計算結果に基づいた避難目的地の有効性を示す評価指標を検討した．評価指標は，避難開始点から避難所までの避難に必要な時間（リードタイム）と，氾濫計算結果による避難開始点が浸水し始めてから避難目的地が浸水するまでの時間差との差分を用いた．検討の結果，自治体が指定する避難所の一部は被災リスクが高く，地域住民にとって避難目的地として決定しにくいと推察された．一方で，一次・二次避難目的地として十分有効な避難所指定の無い地点をいくつか見出すことができた．

This study analyzes the information of debris flow and flood current compound flood control strategy in city streets on the same Timeline, calculates the prediction probability of debris flow and flood range in narrow road and bridge parts, and analyzes the analysis results of debris flow and flood range in city streets. Debris flow hazard assessment methods are established to assess the impact of debris flow on the environment. In 2010 and 2014, the original plan was to determine the direction of "grain size segregation, drift segregation and construction of debris flow", and to grasp the impact of grain size segregation and drift segregation on the transportation and segregation of debris flow. Two types of matching between upper and lower sections can be set. The matching water path is used. A plurality of measurement points in the downstream section of the matching point are used. The concentration of soil and sand transported at the head of the debris flow, the depth of flow, the existence of separation of large particles of gravel, and the measurement of the transportation speed of large and small gravel are used. The migration tendency of the water quality of the debris flow is grasped. In addition, the indexing of the characteristics of the debris flow is carried out. As a result, the probability of debris flow size and debris flow component average diameter matching, associated with property change and transition tendency, multiple classification is confirmed. In 2009, the "Evaluation Method for Debris Flow Disaster in Urban Areas" was established in advance, and the evaluation index for the effectiveness of refuge destinations was discussed based on the flood calculation results under the conditions of mountain and river adjacent dense urban areas, Honkawa and Shikokawa floods and debris flow inflow. The evaluation index is the difference between the time required for evacuation from the evacuation start point to the evacuation destination and the time required for evacuation from the evacuation start point to the evacuation destination. As a result of the investigation, the local government designated a part of the shelter to be evacuated, and the local residents decided to evacuate the destination. One side, one side, two times refuge destination.