Research On Early Warning Rainfall Of Mountain Flood Disaster Based On HEC-HMS Model And Characteristic Rain Pattern

Aiming at the problem that the only rainfall pattern specified in the hydrological manual in the study area is not in line with the diversified rainfall process in practice,this paper deeply explores the characteristics of rainfall time distribution in the Xiaoli River Basin,and constructs 6 types based on rainfall characteristic parameters.Diversified characteristic rain patterns,input 6 kinds of characteristic rain patterns into the HEC-HMS model and use the hydrological model method to solve the planned early warning rainfall and emergency early warning rainfall and conduct a comparative analysis.The main research conclusions are as follows:(1)Analyzed the characteristics of the time-history distribution of the secondary rainfall in the Xiaoli River Basin,based on the joint control of rain-type characteristic parameters to construct the front centralized type,front decentralized type,center centralized type,center decentralized type,rear centralized type,and reliable There are 6 types of post-decentralized rain patterns,and it is concluded that the most likely rain type in the Xiaoli River Basin is the later decentralized type,followed by the later concentrated type.(2)The HEC-HMS model of the Xiaoli River Basin was established.Under the conditions of dry,normal,and humid soil water content,the Nash efficiency coefficients of the regular and verification periods of the secondary flood simulation were greater than 0.8 and 0.7,and the pass rate was 95%、100%,reaching the second-level forecast accuracy,indicating that the model can be used for secondary flood simulation in the Xiaoli River Basin.Sensitivity analysis of model parameters by Morris screening method shows that the main sensitive parameters are CN,storage constant K,basin lag time LLag,and receding point ratio.Among them,CN is the most sensitive parameter,which has a greater impact on flood peaks and flood volume;The basin lag time LLag is very sensitive to the peak present time,and other parameters have no effect on the peak present time.(3)Based on the hydrological model method,the influence of soil water content,rain pattern characteristics,and early warning period on the planned early warning rainfall and emergency early warning rainfall has been deeply studied.The results show that:① As the early warning period increases,the planned early warning rainfall gradually increases,And the emergency early warning rainfall gradually decreases;②The planned early warning rainfall in each early warning period decreases with the increase of the soil moisture content in the previous period,while the emergency early warning rainfall is the opposite;③The earlier the rain peak is,the planned early warning rainfall and emergency early warning are obtained The greater the rainfall;④Under the same soil moisture content and the same early warning period,the larger the catchment area of the basin,the greater the early warning rainfall;⑤ As the early warning period is longer,the comprehensive impact of shape characteristics and rain peak position on planned early warning rainfall and emergency early warning rainfall is more serious,far greater than the impact of soil moisture content on the early warning rainfall.