Automatic Modeling Method Of Rain-flood Numerical Model Based On Remote Sensing Images And Topographic Data

In recent years,with the change of global climate and the acceleration of urbanization,flood disasters caused by various factors are one of the most serious natural disasters in China.However,with the gradual enhancement of people’s awareness of disaster prevention and mitigation,the research on urban flood forecasting and early warning and simulation calculation is also developing rapidly.Storm Water Management Model(SWMM)is the most widely used urban rainfall runoff simulation tool,but the model has poor connection with traditional data processing software,the early modeling process is complex and cumbersome,and many parameters need manual setting.In view of the existing problems,by analyzing the SWMM engineering calculation file format and data arrangement,the SWMM input file data construction method,parameter setting method and the connection between calculation units are mastered.An automatic modeling method based on remote sensing images and terrain data is developed.This method is based on the general digital elevation model(DEM),and the terrain grid is generalized into sub catchment units.The runoff path in the catchment area was judged by the improved D8 algorithm according to the terrain elevation and the distribution position of the rainwater inlet,and the terrain depression was corrected by the three-direction search method.The key parameters,such as the proportion of imperviousness,depression filling amount and infiltration,are determined by fu sing the data of fine land use types.Among them,the land use types in the study area are classified and identified by DeepLab V3+model based on computer deep learning semantic segmentation.The classified labels of remote sensing image data are transformed into numbered information files of different land use types as one of the input data of this method.Based on Visual Studio platform,C++ program is designed and implemented to read basic data,calculated model parameters and generate model engineering input files.By automating the model construction process,the modeling time is greatly shortened,and some parameters of hydrological and hydraulics in the calculation engineering documents can be preset,which further reduces the setting and calibration time of parameters in the simulation calculation process,and overcomes the shortcomings of incompatible basic data of traditional modeling,uncertain parameter values,and time-consuming and labor-consuming modeling process.Taking Tianfuheyuan District of Xi’xian New District as the study area,the method is verified according to the measured rainfall runoff data from September 16,2017 and September 26,2017.The relative error of peak flow and Nash efficiency coefficient of discharge process are used as indicators to evaluate the method.The results show that under 0916 rainfalls,the relative error of peak flow is 1.32%and the Nash efficiency coefficient is 0.881 compared with the measured flow process.Under 0926 rainfalls,the relative error is 1.19%and the Nash efficiency coefficient is 0.852.The error between the simulation results and the measured results is small,indicating that the automatic modeling method is effective.This method is further applied to the sponge demonstration area of Feng’xi New Town,and the comparison and analysis between this method and the traditional modeling method are carried out.The results show that under the condition of 24 h rainfall once a year,the relative errors of each discharge between the rapid modeling method and the traditional modeling method are within±2%,and the calculated Nash efficiency coefficient is greater than 0.8.Under the condition of 24 h rainfall once in five years,the relative errors of each discharge between the rapid modeling method and the traditional modeling method are within±5%,and the calculated Nash efficiency coefficients are all greater than 0.8.The fitting results of the calculation results under both conditions are good.Through the above examples and applications,the accuracy and reliability of the calculation engineering documents obtained by this method are verified.At the same time,this method greatly reduces the time of pre-modeling and greatly saves the labor cost of pre-modeling,which is of great significance in the rapid simulation of urban stormwater.