Prediction And Early Warning Of Mountain Flood Disasters In Xihe River Basin Based On HEC-HMS Hydrological Model

Implementing and establishing an effective forecasting and early warning method(model)of mountain torrent disaster to reduce casualties and economic losses caused by mountain torrent disaster has always been the focus of mountain torrent disaster prevention and control planning.At present,it is different from the methods that used to rely on historical flood disaster data.In the field of mountain torrent forecasting and early warning technology,related technologies based on disaster formation mechanism have been gradually developed.The research on the mechanism of mountain torrent disaster and the application and popularization of forecasting and early warning technology have become a hot direction in this field.Liaoning Province has been plagued by floods since ancient times,especially in the southeastern hilly areas.Many areas in Liaoning Province are not only the place where all kinds of mountain torrents occur and bear disasters,but also the source of flood disasters in downstream areas.Benxi City is one of the areas most seriously affected by mountain torrents in Liaoning Province.Because of the concentrated distribution of mountain areas,narrow riverbed,steep slope and insufficient vegetation coverage in surface soil,mountain torrents occur frequently in Benxi City.In addition,some villages are in remote geographical location,relatively weak economic capacity,low flood control standards and poor disaster prevention measures,which make it difficult to make progress in disaster prediction.This paper takes the Xihe River Basin across Liaoyang,Dandong and Benxi in Liaoning Province as the research object,and takes the Qiaotou Hydrological Station in Benxi County as the research area.Based on the DEM digital elevation model and GIS platform of Xihe River Basin,two HEC-HMS hydrological model schemes were constructed by extracting digital watershed information such as watershed water network and sub-watershed,collecting information of land use type and soil type in the watershed.The two schemes are as follows.Scheme 1: Initial loss and post-loss method,Snyder unit line method,backwater curve method,Muskingen method.Scheme 2: SCS curve method,SCS unit line method,backwater curve method and Muskingen method.The rainfall-runoff processes of seven regular floods and five validation floods in the Xihe River Basin during 1970-2012 were simulated using the above two schemes,and the results of the two simulation were compared and analyzed.The results of the two schemes meet the requirements of the Standard for Water Forecasting.It is considered that the HEC-HMS hydrological model is suitable for mountain flood forecasting in the Xihe River Basin and can be used in practical work.The main results of this study are as follows:(1)The interannual variations of precipitation,runoff and other hydrological elements in the Xihe River Basin are large and unevenly distributed during the year.Rainfall is concentrated in April-September,accounting for about 85% of the total precipitation in the year.By comparing and analyzing the results of critical rainfall calculation,it is concluded that the critical rainfall value calculated by regional method is closer to the warning interval of the current rainfall value in the basin,and is suitable for the Xihe River Basin.Because of the poor representation of the river basin and other factors,the calculation results of single station method are generally low,and its practicability is not strong in the Xihe River basin.(2)According to the characteristics of rainwater and flood in the Xihe River Basin,the HEC-HMS hydrological model is used to generalize the rainfall-runoff process in the Xihe River Basin,and two schemes are used to simulate the historical flood process in the Xihe River Basin.The results show that the first scheme performs better on the whole,with the qualified rate of peak discharge 91.67%,the qualified rate of runoff depth 91.67%,the qualified rate of peak current time difference 100%,and the average certainty coefficient 0.79.The second scheme has a slightly lower accuracy,with the qualified rate of flood peak discharge 83.33%,the qualified rate of runoff depth 91.67%,the qualified rate of peak current time difference 83.33%,and the average certainty coefficient 0.75.(3)According to the comparative analysis of the simulation results of the two schemes,it is considered that it is more reasonable to use the method of calculating excessive seepage runoff in the Xihe River Basin.In the aspect of confluence calculation,the operation results of the two schemes show that the simulation of flood process caused by short duration heavy rainfall is more accurate.Both schemes have some errors in flood simulation with long precipitation duration in the early stage.The scheme selected in this paper is more suitable for the simulation of Flood Confluence process caused by short-duration heavy rainfall.(4)Through the analysis of the difference in the accuracy of mountain torrent simulation,it is considered that the main reasons for the poor simulation accuracy and large errors are the representativeness of hydrological data,the accuracy of image data,the influence of storage structures and some parameters,such as the value of Maskingen K.