Research And Application Flood Forecasting Based On HEC-HMS And Double Super Model Of Small Watershed

With the continuous intensification of climate change and human activities in recent years,the frequency of mountain torrents in China is increasing day by day.Especially in small watersheds,floods in small watersheds are characterized by sudden rises,falls,sudden arrivals,and short time.It is extremely easy to collapse the levees and cause floods that are difficult to avoid in time.Therefore,research on flood forecasting in small basins is of great significance for prevention and control of mountain floods.It is an opportunity for the emergence of watershed hydrological model to reveal the basic laws of hydrological processes.Domestic and foreign scholars have developed a large number of hydrological models for flood forecasting.However,due to the simple structure of the traditional black box model and the conceptual model,most of them ignore the spatial variability of the model parameters and variables,which cannot reflect the characteristics of the production and sink flow during the formation of storm floods.The application scope of the model is small and the simulation accuracy is low.The distributed hydrological model based on high-precision DEM takes into account the effects of factors such as the underlying surface of the basin and the spatial inhomogeneity of rainfall distribution on the characteristics of the basin's production and sinking characteristics.Therefore,more accurate simulation and prediction of flooding occurred in the vast areas.The HEC-HMS semi-distributed hydrological model and the double super distributed hydrological model are typical representatives of this model.In this paper selected the typical small watershed in Shanxi Province—Beizhangdian Small Watershed as the study area.Through the processing of spatial distribution data such as DEM data,land use and soil types in the study area,extracting digital watershed information from the study area.based on this,a flood forecasting model based on the HEC-HMS model and the double-super model is established,At the same time,20 representative floods in the Beizhangdian Small Watershed Series(1964-2013)were used to parameterize and verify the parameters of the two models,and the flood simulation accuracy and applicability of the two models were obtained respectively,finally,the simulation results of the two models are summarized for further comparative evaluation and analysis of the reasons.The main research contents and achievements are as follows:(1)Construction of Digital Drainage Basin in Beizhangdian Small Watershed.With the aid of the ArcGIS platform,the digital elevation model(DEM)of the study area was sequentially subjected to terrain pretreatment,water flow direction determination,calculation of cumulant amount,extraction of river network,and sub-basin classification.In the end,the Beizhangdian small watershed was successfully divided into 13 areas.Sub-basin.On this basis,continue to process land use and soil type data and use Tyson's polynomial method to calculate the area weights of each rainfall station,establish soil properties and related spatial distribution databases,and complete the construction of a digital watershed.(2)Establishment and Application of HEC-HMS Flood Forecasting Model.Based on the analysis of the mechanism of production and convergence of the HEC-HMS model,SCS curve method(SCS-CN method),SCS unit line,exponential decay base flow,and Mussingn method are selected in order to complete the calculation of the production flow,slope confluence,base flow and river confluence in the small watershed.Combined with the constructed digital watershed,a HEC-HMS flood forecasting model was established.Use LH-OAT method analysis Sensitivity of model parameters,the sensitivity analysis results show that the CN value is the most sensitive parameter in the model and has a positive correlation with the peak flood flow and total flood volume.The second most sensitive parameters are the Lag time and the slope K of the storage curve,and both of them have a negative correlation with the peak discharge,total flood and peak present time.Based on the results of sensitivity analysis,the parameters of the model were optimized and the representative 20 well floods were selected from the long series of data in the study area(1964-2013)to parameterize and validate the parameters of the HEC-HMS model.12 of them are used for model parameter calibration and 8 are used for model simulation verification.The simulation results show that the HEC-HMS model achieves good simulation results in both regular and validation periods,and the model simulation accuracy reaches class B.(3)Establishment and Application of Double Super Model Flood Forecasting Model.Based on the analysis of the production mechanism of the double-supermodel,based on the extracted digital watershed information and the spatial distribution data after processing,a double-supermodel model for flood forecasting was established.The Nash instantaneous unit line method was adopted for the confluence model,and the water was used for river channel flood calculation.Literary model SWAI1.At the same time,the sensitivity of the model parameters was analyzed by LH-OAT method.The results of sensitivity analysis showed that the maximum infiltration rate Sr,soil saturated hydraulic conductivity KS,and watershed normalized curve index b were all three parameters.The sensitivity parameters,and the parameters Sr and KS are negatively correlated with the peak discharge and the total flood;the parameter b is positively correlated with the peak discharge and total flood.According to the results of parameter sensitivity analysis,the 20-flood floods of the same series as the HEC-HMS model were selected from the long series of hydrological data(1964-2013)in the Beizhangdian small watershed for parameter verification and verification of the double-super model,of which 12 were used The parameters of the model are determined.Eight fields are used for the simulation of the model.The simulation results show that the double-super model achieves a good simulation effect both in the periodic rate and the validation period,and the model simulation accuracy also reaches class B.(4)Comparison of HEC-HMS model and double-supermodel simulation results.According to the criterion for the classification of floods in the "Code for Forecasting Hydrological Information"(GB/T 22482-2008),the 20 floods selected will be divided into three types: large,medium and small.On the one hand,the simulation results of the two models are analyzed as a whole.In calibration period 12 flood simulations,both the HEC-HMS model and the double-super model are qualified in 9 fields,the qualification rate is 75%,and the qualification rate reaches the level B accuracy;During the 8-phase flood simulation period of the verification period,the HEC-HMS model and the double-superheat model all qualified 6 fields,the qualification rate was 75%,and the qualification rate reached Grade B accuracy.The simulation results show that the simulation accuracy of both the HEC-HMS model and the double-super-model has reached the second-grade standard as a whole,and both of them have achieved good applicability in the Beizhangdian small watershed.On the other hand,from the perspective of different types of floods,the simulation results of the flooding of the two model rates in calibration period and verification periods were analyzed.The analysis results show that the two models have obvious differences in the simulation accuracy and applicability of different types of floods,Among them,the HEC-HMS model has poor simulation accuracy for large-scale floods,but the simulation accuracy for small-scale floods is higher than that for double-supermodels,and the double-supermodel model has higher overall simulation accuracy for large and medium-sized floods than the HEC-HMS model.