Analysis On Risk Assessment Of Local Flooding And Hydrological Effects Of LID Based On DS

Urban local flooding refers to the phenomenon of inundation in low-lying areas,when the precipitation is beyond the limits of the drainage capacity. The acceleration of urbanization and the dramatic global climate changes made the local flooding problems more obvious. At present, the waterlogging situation in China is austere.Based on self-dependent Digital Water Simulation(DS), the hydraulic model of drainage network was established. Risk assessment of local flooding was achieved and the hydrological effects of LID practices were analyzed.By the means of GIS, the pipeline network model was generalized, the catchments were divided elaborately, non-conventional parameters were determined,the DEM was generated and corrected, and a series of methods of hydraulic modeling were proposed, taking a district in Chenzhou as an example. By model coupled with the inland river, the drainage capacity of current drainage network was evaluated under design rainfall conditions at different recurrence intervals. By using the method of dynamical visual scenario simulation, the submerged depth, area and time were calculated based on the 2D model under the design rainfall condition in 30-years recurrence interval. Disaster risk assessment was carried out for the flooded region which had an accumulated water depth of more than 0.15 m, taking submerged depth,submerged time, regional sensitivities and regional importance as evaluating indexes.The inland river was generalized as virtual open channel. The water lever of the river was regulated by changing the discharge coefficient of the orifice. The effect of inland water level on the drainage capacity of sewer system was analyzed. The results showed that the reasonable connection between inland water and drainage network was important to the safety of drainage during the flood season.The article has carried on the systematic exposition of LID from three aspects including connotation, controlling values of planning and technical measure. The LID simulation module and its computational principles were introduced. The drainage network model was established under different land setting conditions with green roof,sunken lawn, porous pavement and vegetative swale, taking a residential district in Changsha as an example. The influence of different rainfall intensity, intervals and rain peak coefficient on the effect of stormwater control of the above LID practices,on consideration of the load capacity of the pipe network, was evaluated, providingtechnical support for design options of LID system.