Study On Shijiazhuang Rainstorm Waterlogging Fine Model And Risk Impact Index

In recent years,Shijiazhuang City suffered a gradual increase in extreme weather,and short duration of local heavy rainfall occurs more frequently.These led to large-scale urban waterlogging and serious losses.Based on the analysis of the waterlogging disaster and risk in the city of Shijiazhuang,this paper has carried out the meticulous simulation and risk impact index analysis of the storm waterlogging in the main urban area of Shijiazhuang.The main achievements are as follows:This paper studied the basic theory and method of fine simulation of waterlogging in rainstorm,and used small structured grid to establish fine urban storm waterlogging model on the base of high precision DEM data.Control equation of the model is a two-dimensional shallow water equation along the water depth based on the Navier-Stokes equation.The finite difference method is used to discretize and solve the formula.The model accurately reflects the housing construction,urban roads,interchanges,drainage canal system and other typical urban geographic elements.The model accurately simulated various phenomena with typical urban characteristics,such as the flow blocking by building construction,the rainwater outflowing from courtyards,the catchment and waterlogging in low-lying area for the instance of underpass bridges and overpass,waterlogging routing on urban roads,and flood water’s drainage by pipe network and pumping stations.Urban waterlogging area,waterlogging position and flooded roads were calculated and counted.This paper divided the waterlogging risk in Shijiazhuang into three levels,high,medium and low.Based on the simulation results of the refined model,risk analysis and risk zoning were carried out.The risk distribution rules of Shijiazhuang City in specific rainfall scenarios were analyzed and the high risk areas in Shijiazhuang City were sorted out.The research results provide the information support for the work of waterlogging disaster reduction and waterlogging risk management in Shijiazhuang City,which has important practical value.Based on the waterlogging disaster in Shijiazhuang City,the main influencing indexes of waterlogging risk in main urban area were analyzed and compared.The influence of water depth,accumulated water duration,heavy rain recurrence period and urban underlying surface were studied after comparison and optimization.According to Shijiazhuang city overall development plan,this paper designed the corresponding calculation schemes group to simulate the formation and evolution of urban storm waterlogging in different scenarios.The temporal and spatial distribution of flooding depth and waterlogging risk and the influence and rule of index change are analyzed in detail.It is found that the frequency and intensity of flood disaster are mainly determined by the rainfall intensity index.The area of the risk area increased by 44.85%,27.99%,17.89% and 7.15% respectively when recurrence interval of the heavy rain in Shijiazhuang City was 5,10,20,50 and 100 years.The change of urban underlying surface has a considerable influence on the degree of urban waterlogging.However,for the low frequency rainfall scenario,the area and distribution of the risk zone are weakened with the underlying surface elements,when hardening ratio of the underlying surface exceeded a certain extent.Finally,based on the variation of roof greening rate and permeable pavement rate in the context of low-impact development of the city,waterlogging simulation and brief risk assessment were carried out.The effect of roofing greening and large-scale permeable pavement on waterlogging reduction was discussed.With the roof greening rate and permeable pavement rate increased,the area of risk areas continued to decrease,but the decline was small;green roof in different types of areas has different effect on flood mitigation;pavement ratio increased,decline of the risk area also increased.