Proposal of flood and sediment discharge predicting method to quantify disaster risk increased by climate change

2023 Fiscal Year Final Research Report

• Project/Area Number: 20H03019
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 40010:Forest science-related
• Research Institution: University of Tsukuba
• Principal Investigator: Uchida Taro 筑波大学, 生命環境系, 教授 (60370780)
• Co-Investigator(Kenkyū-buntansha): 齋藤 仁 名古屋大学, 環境学研究科, 准教授 (00709628) ; 山川 陽祐 筑波大学, 生命環境系, 助教 (20611601) ; 浅野 友子 東京大学, 大学院農学生命科学研究科(農学部), 講師 (80376566)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 気候変動 / 土砂災害 / 山地流域 / 斜面水文 / 土砂流出 / 土石流

Outline of Final Research Achievements

Recently, damage caused by debris flows, landslides, and flooding has become more frequent due to climate change. Furthermore, there are concerns that the scale of rainfall will increase due to climate change. Therefore, it is considered important to quantitatively evaluate future risk of disasters caused by debris flows and floods with an increase in the scale of rainfall. In this study, we have attempted to clarify the changes in water and sediment runoff phenomena that accompany an increase in the scale of rainfall through hydrological observations and analysis of disaster data. As a result, we have empirically demonstrated that the relationship between the scale of rainfall and the scale of water and sediment discharge phenomena is strongly nonlinear, and that water and sediment discharge phenomena can be classified into four stages depending on the scale of rainfall. Based on this, we have demonstrated the importance of evaluating disaster risk by taking these stages into account.

Free Research Field

砂防学

Academic Significance and Societal Importance of the Research Achievements

豪雨時の山地流域の水・土砂流出現象と降雨規模の関係について、包括的な研究は従来限られていた。これに対して、本研究では、現地水文観測、災害前後の航空レーザー測量データを活用した土石流ピーク流量の推定および流出土砂量の空間分布様式の把握、災害記録の分析といった複数の手法を組み合わせることにより、比較的降雨規模が小さい年に数回発生する豪雨から、数10～100年一度といった極めてまれな豪雨による現象まで包括的に研究した。その結果、降雨規模の増大にともなう水・土砂流出現象に及ぼす影響を実証的に示すことができた。これは今後の気候変動による災害リスク評価の基礎となる知見であると考えられる。