从“城市看海”到“城市看江”:极端暴雨情景下福州市洪涝过程模拟与风险分析

From“looking at sea in city”to“looking at river in city”:Simulation and risk analysis of flood and waterlogging process in Fuzhou City under extreme rainstorm scenarios

受气候变化、快速城市化以及基础设施建设滞后的多重影响,我国城市面临的洪涝形势十分严峻。2021年7月17日开始,河南省遭遇持续性极端强降雨,特别是郑州市“2021.7.20”特大暴雨洪涝灾害,使得“城市看海”问题又一次出现在公众视野中,而且由于汹涌奔腾的洪水,城市街道变成了一条条水流湍急的江河,“城市看江”又成为城市洪涝灾害中新的威胁,大量的城市基础设施遭到毁灭性破坏,数千车辆化为废铁,经济损失惨重,“城市看江”的危害远远超过“城市看海”。对近年来我国城市极端暴雨洪涝事件进行了较为系统的梳理,并以沿海城市福州市江北城区为例,参考本次郑州市遭遇1000年一遇特大暴雨降雨过程,模拟计算了福州市城区管网、河道、地面在遭遇类似郑州市“2021.7.20”特大暴雨的500年一遇乃至1000年一遇强降雨下的洪涝过程。然后,基于最大淹没水深与最大流速评估城市洪涝风险。结果表明,在极端暴雨工况下,福州市江北城区淹没十分严重,“城市看江”不容小觑,应当未雨绸缪,提前做好应急防汛预案,工程措施与非工程措施并举,减少洪涝灾害对城市经济的影响,保障城市居民生命财产安全。本研究可以为城市遭遇极端暴雨时的防洪决策工作提供一定的参考。

Affected by climate change,rapid urbanization and lagging infrastructure construction,Chinese cities are facing a significant challenge from urban flood and waterlogging.Since July 17,2021,Henan Province has experienced sustained extreme heavy rainfall,especially the“2021.7.20”rainstorm and flood disaster in Zhengzhou,which made"looking at sea in the city"in the public view again.Moreover,due to the turbulent floods in the streets,the urban streets become turbulent rivers,and a large number of urban infrastructure were destructively damaged,thousands of vehicles turned into scrap metal and suffered heavy economic losses.The harm of“looking at the river in the city”is far worse than“looking at the sea in the city”.This paper systematically explores the urban extreme rainstorm and flood events in China during past years,and takes the urban area in the north of Min River,the coastal city of Fuzhou City as the study area,with reference to the 1000-years return period rainstorms in Zhengzhou City,simulates and estimates the flood process of pipe network,river channel and ground in Fuzhou City under the rainstorm with 500-years and 1000-years return periods.Then,the urban flood risk is assessed based on the maximum inundation depth and maximum velocity.The results show that under the extreme rainstorm condition,the urban area of Jiangbei is flooded seriously,and the"looking at river in the city"can not be ignored.We should take precautions,prepare the corresponding emergency flood prevention plan in advance,and take both structural and non-structural measures to reduce the loss of urban economy,life and property as much as possible.This study will provide useful reference for flood prevention decision-making when extreme rainstorms occur in urban area.