Hydraulic Characteristics of River Flood Flows under Storm Conditions Assuming a Super Typhoon

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K20451
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0303:Civil engineering, social systems engineering, safety engineering, disaster prevention engineering, and related fields
• Research Institution: Tokyo University of Science
• Principal Investigator: Kashiwada Jin 東京理科大学, 理工学部土木工学科, 助教 (10774549)
• Project Period (FY): 2021-08-30 – 2023-03-31
• Keywords: スーパー台風 / 気候変動 / 氾濫リスク / 三次元河川流計算モデル / 吹送流 / 風影響

Outline of Final Research Achievements

This study investigated the hydraulic characteristics of river flood flows during the simultaneous occurrence of flooding and strong winds during a super-typhoon attack. To accurately evaluate the effects of wind on flood flows, three-dimensional flow simulations were performed for an ideal channel and an actual river channel. The analysis focused on the development of the drift current and the increase in water level in several wind conditions; forward, headwind, and crosswind in the direction of the river’s own flow. In the actual river, the results indicate that the wind influences the flow velocity and the water level, and that the increase in water level caused by the wind during the rising stage could propagate as surface waves and remain until the peak of the flood.

Free Research Field

水工学

Academic Significance and Societal Importance of the Research Achievements

気候変動の影響予測は水工学における重要なテーマの一つである．将来の洪水氾濫リスクを評価する研究では，降水量の増大はモデル上流端流量の増大として，河口部における気圧低下や風の作用はモデル下流端水位（潮位）の上昇として，境界条件を見直す形で考慮されているが，河川水表面への風応力の作用について考慮した研究例はない．すなわち，既往研究では風影響を無視しており，気候変動影響下における風の取扱いの妥当性には自ずと疑問が生じる．本研究では，洪水流と暴風の同時生起を想定した三次元流動計算を行うことで，風が流動に与える影響を定量的に評価した．その結果は，今後の河川流計算における風影響の考慮の重要性を示唆した．