Simulation And Research Of Mountain Flood Early Warning In Typical Small Watershed In North China Based On HEC-HMS Model

China is a country with frequent mountain torrents,especially mountain areas,and the high frequency of mountain torrents has seriously threatened the economic development of mountain areas.In addition,monitoring hydrological stations is lacking in mountainous areas where flood disasters occur,which results in the lack of prediction data,and increasesing the difficulty of early warning and prediction of mountain torrents.This paper mainly uses the hydrological model HEC-HMS to study the flood simulation of the Tongtian River Basin in Laicheng District of Laiwu City,exploring the hydrological process characteristics of the mountain basin,simulating and analyzing the early warning indexes of the key research objects in the study area,testing and analyzing the early warning indexes according to the measured rainfall data.The main contents are as follows:(1)Summarizing the significance and background of this research,and analyzing the research progress of hydrological models and HEC-HMS models at home and abroad.The rainfall data of the study area are collected to analyze the hydrological characteristics of the basin.The precipitation in the study area is concentrated in the flood season,the distribution is nonuniform in the year,the rainfall in the flood season accounts for 74.7%,the non flood period accounts for 25.3%.The characteristics of flood process in the study basin is that the flood volume is not large,the flood duration is not long,and the runoff is fast.(2)According to the DEM data of 30m*30m in the research area,the HEC-GeoHMS module is used to calculate and analyze the DEM data,creating the digital water system map of the study area,and establishing the HEC-HMS hydrological model of the study area.the initial and constant method,the Synder unit hydrograph,the recession curve and the Muskingum method are adopted respectively in the 4 stages of flood simulation in the study area.using 10 rainfalls and floods to simulate and analyse,among which of 7 use to analyse calibration model,and 3 use to validate model.The model is applied in the key small watershed of number 2 subbasin,obtaineding the peak discharge of key research subjects.(3)Taking number 2 subbasin as an example to calculate and analyze the early warning index,determining the early-warning period of the research objects,and analyzing the soil water content in the study area.According to the measured cross-section,the flood waterlevel and Manning formula to analyze the relationship between water level and flow,and obtaining the critical flow of the research object.According to the HEC-HMS model and the critical flow to backstepping calculate,obtaining the critical rainfall in three cases of dry,general and wet soil water content.Three kinds of critical rainfall are treated with "reduction" treatment,that is critical rainfall is treated with ±10%,to get ready transfer early warning index and immediate transfer of early warning index.(4)Selecting 4 typical floods to check and analyze the early warning index.The critical flow check is mainly to check the water level flow process,including checking the water level flow calculation method,the river roughness and the river specific drop,the results of the critical flow test in the 4 test objects are all reasonable.The flood process mainly check the applicability of the model and the rationality of the parameters.Using the 20160722,20120708,20030904 and 19960730 flood to analyse and check the early warning index:from the critical rainfall deviation analysis,the early warning index of the Guanzheng village was larger,The early warning index of the Fanggan village is between the 19960730 rainfall and the 20160722 rainfall intervals,the index of early warning of Anziwan is smaller;From the rainfall frequency of critical rainfall interval analysis,the early warning index of 3 research objects are in a reasonable range.According to the simulation results of this study,the HEC-HMS hydrological model has a good applicability in the hilly area,and it can be applied to simulate the early warning index of the actual Mountain Hilly Basin;According to the analysis of the results of 4 typical rainfall flood to verify early warning indexs in this study,the analysis of early warning index in conditional areas can use multiple rainfall floods to repeatedly verify to accurate the range of early warning indexs.