Risk Identification And Early Warning Research Of Flash Flooding Disaster In Town Field Of Mountain

Flash flood is the surface runofl,which is the result of a sudden burst of rainfall caused by rain in the mountain watershed.Flash flood disaster has always been the center of attention of society because of its sudden, difficult to predict the prevention, frequent occurrence of disasters and serious losses and other characteristics. According to the statistics of the State Flood Control and Drought Relief Headquarters,in recent years,flash flood disaster caused by heavy rainfall occurred frequently in China,and the annual average number of deaths caused by mountain torrents accounted for about 80% of the total number of flood deaths, the number of people accounted for the proportion of the national flood death toll increased,it has become an important issue that limits its economic growth and sustainable development for hilly areas.For the disaster form of mountain river flood, this paper will analyze and study the identification risk zones and early warning indicators combined with a engineering example.The main contents are as follows:(1) This paper introduces the calculation methods of storm flood, such as rational method,instantaneous unit hydrograph method and hydrological model method, and calculates the design flood characteristic value of standard duration according to five typical frequencies.(2) According to the typical frequency flood peak level and population and housing distribution along the elevation , analysis and evaluation of disaster prevention object flood control capacity; put forward the classification of dangerous levels, and for disaster prevention objects to identify the risk zone.(3) Propose a typical method for determining early warning indicators: the method of watershed hydrological model based on HEC-HMS According to Arcgis and Digital Elevation Model (DEM) to extract the watershed to establish a digital watershed model,the method of watershed hydrological model is used to calculate the runoff yield , confluence, base flow and river channel evolution.By assuming the amount of rainfall, simulates flood process on control section,with continuous trial until the flood peak is equal to the critical flow rate,where the rainfall is the critical rainfall.In this paper, considering the influence of the previous rainfall, two critical values (Pa = 0.5Wm and Pa = 0.8Wm) are selected to simulate three kinds of conditions.(4) The actual engineering application.This paper is based on the small watershed of Baoshi Village in Yanbian County, Panzhihua City,Gesala Yi Township town as the typical object of disaster prevention .According to the analysis of the relationship between water level elevation, flow rate,population and other factors, building the risk zoning level of mountain torrents,analyzes the critical rainfall early warning indicators of mountain torrents disaster by using HEC-HMS watershed hydrological model,the results show that the watershed hydrological model based on HEC-HMS has a good application prospect in the determination of early warning indicators of small watershed in hilly area, and has a good promotion value.