| In recent years,with the intensification of climate change and the acceleration of urbanization,the extreme rainfall has occurred frequently,and the flood disasters have caused greater loss of life and property.At the same time,with the improvement of computing performance and computing methods,the rainfall numerical model has become an important technical approach to research flood and inundation problems.However,the fine terrain and drainage-pipe network data in urban areas is very difficult to obtain,which greatly limits the application of the rainfall numerical models.In this paper,in view of the current situation of insufficient simulation of flooding processes in ungauged catchments,a set of simulation methods that are suitable for ungauged catchments,with better accuracy,and simpler simulation methods is taken as the goal.Based on the full hydrodynamic rain and flood simulation developed by Xi'an University of Technology,a novel artificial friction approach suitable for fine terrain missing areas and an equivalent drainage method suitable for areas with missing pipeline networks are proposed.The proposed methods verified by a basic example improve the accuracy of the simulation in the catchments with missing fine topographic and pipeline data.A novel artificial friction approach based on rough DTM terrain is proposed,through theoretical analysis and formula derivation of the friction term in the shallow water equation.The sensitivity on the correction coefficient with the different parameters of unit width discharge,slope,building density and grid size are analyzed respectively.It was determined that the correction coefficient was not sensitive to grid size.The relationship between the correction coefficient and the slope,building density and unit width discharge is obtained by nonlinear fitting.The approach was verified by the flood process of the ideal urban catchment and the Toce River physical model test area.The results show that the accuracy of water depth simulation at different points and sections using the novel artificial friction approach is significantly improved.The proposed approach is expected to be an efficient simulation method for flood evolution in areas where fine terrain data is missing.Based on the principle of water balance,all area equivalent drainage approach,road equivalent drainage approach,and inlet equivalent drainage approach are proposed,and these approaches are applicable to pipe network data missing areas.The above approaches only need to deal with the rainfall source items in the two-dimensional surface model,and the inlet equivalent drainage approach can be modified according to the design pipe network standard or measured data.Three approaches were used to simulate the rainfall and runoff processes in the ideal urban catchment and the actual catchment in Fengxi New City,respectively,and compared with the results of the coupled model.The results show that inlet equivalent drainage approach has the best simulation effect,followed by the road equivalent drainage approach,and the all area equivalent drainage approach has a poor effect.Compared with the coupled model,the equivalent drainage approaches proposed in this paper is simple and effective,and can provide a theoretical basis for the simulation of the rain and flood process in the area where the urban pipe network data is missing.Combined with the available topographic data and high-precision image data,through the extraction of features such as buildings,trenches and inlets,it is possible to conduct a numerical simulation of the flooding process in a completely no data catchments.In this paper,through the construction of the surface artificial friction approach and the underground pipeline network drainage process generalization approach to carry out numerical simulation research on the rainwater and flood process in ungauged catchments,it can provide technical support for the planning,design,management,operation and maintenance of the urban area with missing data. |
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