摘要
2022年8月18日凌晨,青海省西宁市大通回族土族自治县发生山洪灾害,导致 26 人死亡、5 人失联,这是典型的小溪小河发生灾害造成多人伤亡事件.降雨叠加是此次山洪灾害的直接原因,前期连续降雨使土壤含水量达到或接近饱和,2022 年 8 月 17 日晚超历史记录局地短时强降雨难以通过土壤下渗或被植被截留,形成山洪灾害.综合分析遥感数据、数字高程模型、现场数据和媒体数据发现,山洪区具有汇水面大、河谷狭窄、相对高差大、河道较浅、障碍物多等特征,造成山洪势能大、运动距离长、局地雍水外溢严重,致使沟道两侧部分房屋、农田、道路等被冲毁.全球变化背景下,西北干旱区、青藏高原等山洪低风险区降水量显著增加,局地短时强降水时有发生,小溪小河发生山洪甚至特大山洪风险形势日益严峻,如再次遭遇强降雨灾区存在山洪灾害复发风险.
Abstract
In the early morning of August 18,2022,a flash flood occurred in Datong Hui and Tu Autonomous County,Xining City,Qinghai Province,resulting in 26 deaths and 5 missing.This flash flood is a typical event of multiple casualties caused by a creek disaster.The superimposed effect of rainfall directly led to this flash flood.The early continuous rainfall caused soil moisture content to reach or approach saturation.On the night of August 17,2022,local short-time heavy rainfall smashing historical records,which could not infiltrate into the soil or be retained by vegetation,resulted in a flash flood.As revealed by the comprehensive analysis of remote sensing data,digital elevation model,field data,and media data,the flash flood area exhibited a large catchment area,a narrow river valley,a high relative height difference,a shallow river channel,and many obstacles.Consequently,the flash flood manifested high potential energy,a long movement distance,and locally severe backwater overflow,destroying some houses,farmland,and roads on both sides of the river channel.Against the backdrop of global changes,low-risk areas of flash floods,including the arid region of northwest China and the Qinghai-Tibet Plateau,display significantly increased precipitation and frequent local short-time heavy rainfall.Hence,creeks in these low-risk areas are exposed to increasing risks of flash floods and even catastrophic ones.Additionally,heavy rainfall might induce the recurrence of flash floods in disaster areas.
万方数据