Research On Urban Flood Refined Simulation System

Under the background of global climate change and the rising level of urbanization in China,the flood problem has become one of the most important natural disasters which affecting the normal operation and development of the cities.With the continuous improvement of the urbanization level,flood disasters often cause serious casualties and huge economic losses.The public has put forward higher requirements on urban flood management.How to reduce casualties and property losses caused by urban flood through fine urban management has attracted much more attention.As an important technical measurement tackling with the urban flood research,how to support the scientific decision-making of the urban flood control by constructing a refined urban flood model has become one of the most urgent technical problems in the field of hydrology and disaster prevention&reduction.Focusing on the current problems of urban flood simulation,such as the current situation of widely used over-generalization method of urban flood simulation,the paper constructs a physically-based city flood refined simulation technology system from the aspects of net rain production,slope flow concentration,river channel routing,pipe network flow routing,and flood control structure operation.In order to simulate the physical processes of stratified flow generation and concentration of complex multi-layer structures in urban areas,the research on the grid-based layered computing technology was carried out.Facing with the complex situations of urban municipal pipe network data conditions and the difficulty in obtaining pipe network data inside the block,combined with the physical mechanism and the generalization method of drainage,this paper gives a method for simulating urban surface drainage under different conditions of different blocks and roads.Combined with the complicated drainage processes of urban surface,five basic urban catchment areas with static concept and the flow concentration area of any location on the surface of the dynamic concept are proposed,and the division method is studied.From the point view of the complex real-world problems such as urban flood data and boundary conditions,this paper proposes the urban flood refined model integration technical framework from model nesting simulation method and modular modeling.Furthermore,it is applied to the case study of refined urban flood model under four different surface drainage methods.The paper mainly achieved the following results:(1)Combining the flood simulation principle and method,the urban flood refined simulation system with physical mechanism is studied.Combined with the current situation of urban surface runoff production and flow concentration method,this paper puts forward the construction method of surface runoff production and refined model from the aspects of surface grid model construction with real physical meaning,flow concentration model construction and terrain model construction.The river channel refinement model construction method is given from two aspects:high-precision data acquisition and processing method and refined river routing model construction.The research on the refined construction method of the pipe network model from the rainwater inlet,rainwater inspection well,pipe network outlet,underground storage water body and rainwater drainage pipe(channel).A method for constructing the relative "water level-capacity" relationship of water bodies under the condition of ungauged basin is proposed.Finally,a detailed simulation method for urban flood engineering scheduling is proposed from the aspects of dam operation,pumping station scheduling and joint scheduling.(2)The surface multi-layer modeling technology is proposed from the aspects of grid layer construction,surface layered runoff production,surface layered confluence,grid-to-pipe network layered coupling and upper-layer drainage.The accurate real physical model of complex rainfall runoff production and surface confluence of multi-story structures such as overpasses and underground spaces has been implemented.The surface layered grid modeling method is applied to the calculation of overpass water,and the calculation result is proved obviously better than the single layer grid model.(3)The research on urban surface drainage simulation methods under different data conditions is carried out.Based on the physical surface drainage model of "surface-rainwater inlet-pipe network",two generalization methods are proposed:the "surface-pipe" based on the rainwater catchment area of inspection well or rainwater inlet,the "surface-river" based on the rainwater catchment area of pipe network outlet.Combined with the key factors affecting the drainage calculation of the pipe network model,the comprehensive evaluation method of pipe network data quality is given from the point view of the completeness and accuracy.Based on the above-mentioned studies,the calculation method of road drainage under different pipe network data quality conditions is proposed.Finally,from the point view of the current situation that the pipe network data inside the block is difficult to obtain,combined with the data conditions of rainwater municipal pipe network and the method of road inundation modeling,the generalization method of surface drainage calculation in urban blocks was further proposed to make up for the surface drainage capacity under the condition of the missing pipe network data in the block area.(4)Combining the complex process of urban and rural surface runoff production and confluence,the dynamic concept of urban rainwater catchment area and the refined method of static concept are studied.On the basis of data collection and standardization processing,pipe network connectivity analysis,surface watershed analysis,etc.,according to the principle of"smallest catchment route",combined with virtual inspection well technology to integrate water system,water body(lake,stagnation water body)and terrain(multi-factors such as water-blocking roads,drainage works(pumping stations,etc.)improve the existing method of dividing the catchment area.The dividing method of the static concepts of these five basic watersheds in cities is proposed.Then,combined with the physical process of urban surface confluence,with the help of urban flooding refinement model,based on the concept of instantaneous water accumulation contribution and cumulative water contribution,the dynamic concept of the rainwater catchment area at any location on the surface is proposed and applied in analysis of waterlogging in the city.Finally,the extraction method of pumping station drainage service area is introduced.(5)From the two aspects of nested simulation method and modularized modeling method,the framework of urban flood refined model integration technology is proposed.The nesting simulation method of urban floods is studied from three aspects:model mechanism,coupling mode between models and spatial scale of computing objects.A modularized modeling method is proposed for the more complex Surface Hydraulic Model and Pipe Network Model in urban flood calculation.Finally,based on the urban flooding refined model integration technology,the flood model of the Shenzhen River Basin where the Luohu Community is located is the full basin model and the flood drainage model of the four different cities in the Luohu Community.The comparative analysis of the calculation results shows that the refined degree and precision of the calculation results of the urban flood model of the mixed surface drainage mechanism in the neighborhood are optimal.