Urban Flood Hydrological And Hydrodynamic Model Construction And Flood Management Key Issues Exploration

Floods are natural hazard that happen most frequently in the world.Flood-hit popupation and property loss are increased as the urbanization development and resource gathering to the cities.Due to the hazardness and frequency of urban flood,urban flood has been the current research hotspot and urban flood management has even become the focus issue in urban flood research.As the development of computer technology and numerical technique,numerical modelling has become an important tool for the researches in urban flood.There are lots of researches have been done to enhance the development and progress of urban flood management.Based on the previous researches,this paper summarized some deficiencies of current researches and some questions deserving research,and built a coupled one dimensional(1D)and two dimensional(2D)urban flood model.Through numerical modelling,the formation and development of urban flood,and the advantages and disadvantages of flood management methods are researched and some valueable results are concluded.(1)Based on the deeply research on the calculation theories of SWMM model and SWM model,this paper discussed the coupled methods between these two models,proposed a DLL-based convenient coupled strategy,and successfully constructed the coupled 1D and 2D model.The coupled model was verified through three theoretical cases and two practical cases.Results showed that the coupled model had pretty good performents in five cases,which indicated that the coupled model had high accuracy and good robustness in flood modelling.(2)This paper researched on the running state of drainage system and the variation of urban inundation through coupled model modelling under different rainfall scenarios.To explore the relationships between running states of drainage system and the variation of urban inundation,the main aim was to dig out the urban inundation response for rainfall intensity and rainfall type.Results showed that rainfall types had a great effect on urban inundation.With a later rainstorm peak arrival time,inundation would become more severe(reflected in inundation volumes,depths,and extents).The time lags between the rainstorm peak and inundation volume peak would be shorter with later rainstorm peak arrival times.The main reason was that the drainage capacity became more and more insufficient as the rainfall peak arrival time became later.This study also indicated and reconfirmed the appropriateness of the position coefficient value of design rainstorm peaks in China.(3)Through the coupled model simulation,this paper analyzed the rainfall-induced urban inundation,and researched into the advantage and deficiency of the grey infrastructures such as pipe network improvement and deep tunnel construction.Results showed that both deep tunnel and pipe network improvement could help mitigating urban inundation.However,a deep tunnel could only be used to prevent the inundations that were caused by the backwater effect,whereas enlarging pipe diameter was the solution for the inundations caused by insufficient pipe capacity.Drainage network improvement may lead to higher flood prevention pressure for the downstream area.Source controls of rainwater and increasing pump station capacity were also important for inundation management in riverine cities.(4)Combined with sponge city construction,this paper researched into the hydrologic characteristic and analyzed the runoff control effect of LIDs.Results showed that LIDs could reduce the urban runoff and runoff peak flow effectively.But as the rainfall intensity increased,the reduction efficiency decreased.In the rainfalls with similar rainfall volumes,LIDs would have better reduction rates in the rainfalls with longer duration and lower intensity.In future scenarios,the number of bioretentions and wet pond should increase while the number of green roof and swale should be reduced.And the number of porous pavement and rain barrel had a little change.