Study On Calculation Of Rainfall-Runoff In Dataless Watershed

With China enters the sprint period of the first hundred-year struggle goal,all the preparatory work in the country is in full swing.However,the frequent social activities of human beings are bound to have certain impacts on the natural environment,including the lag of urban flood control and drainage planning.Urban construction runoff,urbanization effects,and flood risks are increasing due to unreasonable construction layout and increased impervious surface.In recent years,the national climate anomaly,flooding caused by heavy rainfall has become one of the severe water problems facing the rapid development of China's urban economy.Therefore,the water problem caused by “rainfall-runoff-flood” in major cities has become Hydrological prediction(PUB),which is a very urgent and important research topic,and where there is no data or scarcity of information,is a hotspot and a difficult point in hydrology and water resources research.Because the data-free areas usually lack the measured runoff data,and can not provide effective data for hydrological prediction,so for the domestic data-free watershed,the hydrological prediction results are often inaccurate and consistent with the actual situation,especially the vast majority of seasonal small watersheds in the northwest.It is even more powerless.Therefore,exploring new ideas,finding new methods,and improving prediction accuracy are important contents for future hydrological prediction research in non-data areas.The project takes the Lanzhou New Area as a research area and conducts a simulation study of the “rainfall-runoff” process.Because the main source of runoff flood in Lanzhou New Area is the natural sand ditch in the upper reaches of the basin,the flood formation is mainly caused by heavy rain.However,there is no historical flood data of the main channel in the basin of Lanzhou New Area,and the rainfall observation is also very scarce.Therefore,the study area is a hydrological analysis of data-free areas.The main contents are as follows:(1)Based on ARCGIS-DEM,the digital characteristics of the Lanzhou New Area water system under natural conditions were extracted,and the basin area was divided with the relevant data,and the typical hydrological control section was selected.(2)Calculation of production flow and convergence(design flood)in Lanzhou New District.Firstly,the rainstorm parameters of Gansu Province were used to check the storm parameters.Combined with the ~face-deep(%)relationship and the watershed shape coefficient curve,the typical hydrological control sections of each area were calculated for 1h,3h,6h and 24 h.The frequency is 0.33%,1%,2%,5%,10%,20%,30%,40%,50% rainfall.Secondly,according to the size of the catchment area of the hydrological control section,the main rain peak distribution type is selected,and then the rain-type table is integrated with thegeneralized time-history of the Yellow River tributary area,and the main rain peak external rainfall is controlled with the same frequency to obtain the flow of different frequencies.Finally,the instantaneous unit line method,the inference formula method,and the multi-factor empirical formula method of small watershed design flood are used to calculate the flooding of different frequencies.(3)Production and sink calculation based on SCS-CN hydrological model.The sensitivity of the model parameters was analyzed using the LH-OAT method.Based on the relevant research results,considering the topographical features and underlying surface conditions,combined with the SCS runoff model and GIS-DEM technology,the typical hydrological sections in the basin area are taken as the research unit,and the model parameters suitable for the Lanzhou new area runoff calculation are recommended and obtained.A more reasonable flow results and convergence results.At the same time,compared with the production and confluence obtained in(2),the analysis shows that the model simulation accuracy is ideal,which is basically in line with the actual rainfall-runoff process in Lanzhou New District.Based on the comparison results,the ideal production flow rate and peak flow rate are recommended.(4)According to the current mountain flood prevention measures and major problems in Lanzhou New Area,the idea of “upstream interception,mid-stream detention,downstream discharge” should be adopted as a whole,and the engineering measures and non-engineering measures are proposed.Simple flood control measures.