“23·7”特大暴雨洪水北京山洪灾害风险预报复盘分析

"23·7"extremely heavy rainstorm flood:A review of Beijing mountain flood disaster risk forecast

受台风“杜苏芮”减弱低压环流和冷空气共同影响,2023年7月29日至8月2日北京市出现特大暴雨。强降雨引发北京西部南部山区发生严重山洪灾害,多条山洪沟出现历史最大洪峰流量。本文在梳理“23·7”山洪风险研判过程的基础上,对基于雨量阈值的山洪风险研判结果开展复盘分析。全市实际发生山洪沟道158条,雨前7月29日17时山洪风险研判有106条山洪沟道为红色风险预警提示,预报准确率为67%。雨后根据实测降雨复盘,全市红色风险沟道有144条,预报准确率为91%,结果可为山洪灾害风险研判、预报预警等非工程防治措施提供参考。

Extremely heavy rainstorm occurred in Beijing from July 29 to August 2 at year 2023 because the combined influence of the weakened low-pressure circulation and cold air induced typhoon"Doksuri".The heavy rainfall triggered severe mountain torrents in western and southern Beijing,many of which were deemed as the largest flood flow in history.On the basis of reviewing the risk assessment process of"23·7"flash floods,this article conducts a retrospective analysis of the results of flash flood risk assessment based on rainfall threshold.There were actually 158 mountain flood channels in the city,and on July 29th at 17:00 before the rain,106 mountain flood channels were identified as red risk warning signs,with a prediction accuracy of 67%.After the rain,according to the actual rainfall measurement,there are 144 red risk channels in the city,with a prediction accuracy of 91%.The rainfall threshold method has played a good warning role.The results could provide a good reference for non-engineering prevention and control measures for risk assessment,prediction,and warning of mountain flood disasters.