Urban flood risk simulation and assessment in cities based on multi rainstorm scenarios

Abstract

[Objective] Flood simulation and risk assessment are recognized as of great significance in addressing urban flood disasters. Utilizing regional hydrological hydrodynamic models to analyze rainstorm scenarios has become a predominant approach in current research. This method aims to improve the computational accuracy of hydrological and hydrodynamic models, thereby enabling more effective multi-scenario analysis. [Methods] Jiangyin City was selected as the study area, and a nested model of the Taihu Lake area model and Jiangyin City flood model were employed to conduct multi-scenario simulations and assessment of urban flood. Considering the three typical rainfall characteristics of long-duration plum rain type, short-duration heavy rainfall, and typhoon rain, a total of 10 working conditions were established across three key scenarios: the “July 20 rainstorm in Zhengzhou, ” extremely heavy rainstorm, and water conservancy design rainfall. A flood model coupled with hydrological and hydrodynamic forces and a two-dimensional river network management network in the study area was constructed. Detailed simulations and analyses of surface waterlogging and associated risk distributions were enabled. [Results] The result indicated that under the scenario of “July 20, Zhengzhou, ” the risk area experienced a rapid rise in water level reaching high peaks, and a prolonged receding process. When subjected to the maximum rainfall magnitude, the inundated risk area within the study area accounts for 37.32%. In the case of the extremely heavy rainstorm scenario, the submerged area were jointly influenced by the total rainfall and the maximum hourly rainfall. At the maximum rainfall intensity, the total risk area accounted for 13.2%, and the submerged water depth reached 0.60 m. Under the rainfall scenario of water conservancy design, the proportion of medium-risk areas was the highest. With the increase of design rainfall, the submerged area of medium-risk and high-risk areas significantly increased. Surface waterlogging in the study area was jointly affected by local rainfall and surrounding rainfall conditions. [Conclusion] The research result revealed the adaptability of Jiangyin to encounter extreme rainstorms and predicted the risk factors under different rainfall scenarios, which can provide a decision-making basis for Jiangyin to formulate targeted countermeasures and measures, thereby enhancing the city's capacity to cope with extreme rainstorm and flood disasters.

Keywords

situational analysis method / flood simulation / risk assessment / Jiangyin City / climate change / rainfall / urban waterlogging / hydrological and hydrodynamic model