The Flash Flood Forecasting Model Under Different Soil And Water Conservation Engineering

Under the influence of rainfall intensity,antecedent soil moisture,underlying surface types,vegetation and land use types,human activities,flash flood disasters occur frequently,and brings serious damages to ecology,environment,social and economic development.Therefore,how to analyze the change law of the flood,establish the optimal prediction model,and forecast the flash flood disaster in time,these become an important subject for hydrological scholars.The data covering from 1964 to 2016 at twelve precipitation stations(Li zhuang,Zhongcun,Xishangcun,Baquan,Beizhangdian,Cuijiazhuang,Xiaanzhuang,Wuer,Guojiazhuang,Wangjiawan,Nanpo,Fangcaogou)and one hydrologic station(Beizhangdian)in Beizhangdian watershed of the Jianghe River in Changzhi city are used as case studies.This paper investigates the characteristics of the flood in watershed and the change law of the flood in different time,analyzes the flood rule using the specific method under the various soil and water conservations.The article selects the flood forecasting method and establishes the forecast model,calibrates and optimizes the parameters,analyzes the sensitivity of the parameters,simulates part of the flood,and the rest of the flood to be used as verify the model.The article analyzes the runoff parameters under the soil and water conservation,consequently achieve the related parameters.The influences on the runoff yield and concentration under the various soil and water conservation engineering,analyze the parameter value in specific model.This paper also studies the parameters of flood forecasting model under the various soil and water conservation engineering.The main contents and results in this study were as follows:(1)The characteristics of the flood in Beizhangdian basin.The paper analyzes the annual variation trend of flood peak,based on the frequencycurve,the flood can be divided into deluge,middle,small three levels.The deluge occurred in the 1960 s,the middle flood occurred in the 1970 s and the frequency was 33.3%.From the1980 s,the small floods frequency gradually increased,the probability of the flood up to94.4%.Analysis of peak flow changes during the year,a small flood mainly occurred in July to August,the flood occurred mainly in July,the main flood occurred in 6,7,8 months.After the implementation of water conservation measures,the flood volume and the peak flow attenuating rang were 10.7% to 42.7% and 19.3% to 75.9%,the attenuating range of the lag time was 100%.It can be seen that the water conservation measures have a significant effect on the reduction of flood volume and peak flow,it can extend the lag time.(2)Model construction of the HEC-HMS in Beizhangdian watershed.According to the Beizhangdian watershed,using the method of numerical simulation based on the model,establish the runoff calculation.Via the model principle,the basin mainly establish the HEC-HMS model,the model used the method: SCS curve number method,SCS unit hydrograph method,index regression base flow method,Muskingum routing method.Construct the scientific and rational hydrological model can lay the foundation for the later flood forecast in basin.(3)Example analysis of the flood forecast in Beizhangdian watershed.From 1964 to 2016,in order to rate the model parameters,combined the objective function method and artificial trial and error method,the paper use the Nelder and Mead algorithm to optimize the parameters,analyze the sensitivity with perturbation method,according forty-four flood series to verify the model.The sensitivity parameters from large to small can be divided into the runoff curve number CN,the Lag Time.As the CN increase,the flood peak and the flood volume increase also.During the period of verify simulation model,the qualified rate was 77.3%,the results can be regarded as standard B,it have great reference value for the future flood forecast.(4)Study the parameters of flood forecast model under the various soil and water conservation in Beizhangdian Watershed.Study the runoff parameters under the soil and water conservation,under the different soil and water conservation engineering,calculate and analyze the runoff,analyze the parameter's value in specific model.From the qualitative influence to see,after the fish-scalepits measure,the sub-basin area increase 15%,CN reduce 3.75%,the production flow ability decline;after the check dam add 15,the lag time extended by 9%,thus delaying the convergence process of the river.