Flood Event-based Scaling Study In Daqinghe River Basin

Flood is one of the most common natural disasters.Flood forecasting is a key non-engineering measure for flood control and disaster reduction.However,in many parts of the world,flood data can't meet the requirements of flood forecasting because of data scarcity.Therefore,the problem of flood forecasting in the ungauged and poorly gauged basins is always a difficult problem to be solved urgently in the field of hydrology.Flood scaling study is an important means to solve the problem of flood forecast in those basins.Taking the mountainous area of Daqinghe River basin as the research object,this paper analyzes the event-based flood scaling.The main research contents and results are as follows:?1?Flood similarity analysis in Daqinghe River basin.Firstly,the flood characteristics of the basin are analyzed,and then the flood similarity of each sub-basin is calculated by principal component analysis.It is found that the similarity between the floods of each sub-basin in the Daqinghe River basin is more than 75%,which has a significant similarity.?2?Flood scaling study in mountain area of Daqinghe River basin.The same flood events of 7 sub-basins in Daqinghe River basin were selected,and the flood peaks after the change point?1979?were reconstructed based on rainfall-runoff relation without the impact of human activities.The regression analysis of the flood peak discharge before and after the change point and sub-basin area was carried out.It was found that the flood scaling existed.The flood scaling exponent was between 0.6545 and 1.3798,and the determination coefficient R² was between 0.5170 and 0.8096.In the regression equation,rainfall depth and rainfall spatial distribution were taken into account in addition to basin area,and it was found that the flood scaling was obviously enhanced.?3?Flood scaling analysis based on hydrological model simulation.Using DEM,soil type,land use type and hydrometeorological data of Zijingguan basin,the HEC-HMS hydrological model was established to simulate the rainfall-runoff process of Zijingguan basin,and model calibration and validation were carried out.The results showed that the relative errors of peak discharge and flood volume were within 20%,the qualified rate of peak time error was 78.6%;and the average Nash efficiency coefficient was 0.77.The model could be used in the Zijingguan basin and had good applicability and high accuracy.Regression analysis was performed on the flood peak discharge of each sub-basin in Zijingguan basin simulated by HEC-HMS hydrological model and the corresponding sub-basin area,and the flood scaling exponent was0.5396⁰.9922.The flood events under two ideal scenarios of uniform rainfall spatial distribution and land surface conditions were simulated,and flood scaling significantly enhanced.The determination coefficient R² was as high as 0.9993,flood scaling exponent under uniform rainfall spatial distribution was 0.5884⁰.9425,while 0.5360⁰.9420?CN=45?,and 0.7105⁰.9450?CN=65?under uniform land surface conditions;The 630806 rainfall event process was selected as the typical one to be amplified using same multiple amplification method.It was found that when the CN value was the same,the scaling exponent increased with the increase of the maximum1h rainfall depth P₁,when the maximum 1h rainfall depth was the same,the flood scaling exponent?increased with the increase of CN value,and finally tends to be fixed at 0.95.