| In the face of global warming and the frequent occurrence of extreme weather,the flood disaster in urban areas is becoming increasingly prominent.At the same time,rapid urbanization and human activities have changed the original natural water cycle process,which leads to a series of problems such as hardening of the urban underlying surface,increase of surface production and flow,serious soil erosion,reduction of flood discharge and flood storage capacity.The phenomenon of "flood must be flooded in rainy season" is becoming more and more serious.To effectively alleviate the problem of urban waterlogging,we need to simulate the urban hydrological process comprehensively and scientifically,and provide strong technical support for urban flood control.This paper takes Fengxi New City,Xixian New Area,the first batch of sponge city construction pilot area in China as the research object,simulated the current situation and the changes of urban waterlogging after adding Low Impact Development(LID)measures,evaluated the construction effect of sponge City,analyzed the causes of waterlogging and put forward countermeasures.The main results are as follows:(1)The pipe network model and surface flow model of Fengxi New City sponge city core pilot area are constructed and coupled by MIKE FLOOD.The model is calibrated and verified by the measured data of the network discharge process and water depth of waterlogging points.The results showed that the model results fit well with the measured values,which shows that the model has good applicability in the analysis and application of urban waterlogging and sponge city construction,and can provide scientific and technical means for engineering practice.(2)Different rainfall scenarios are designed according to the rainstorm formula of Fengxi New City,the influence of different frequency rainfall on the urban flood process is analyzed,and the drainage capacity of the existing network is evaluated.The research showed that the surface runoff and the number of overflow inspection wells increased significantly with the increase of rainfall intensity,and the rainfall intensity is the main factor leading to the increase of surface runoff and node overflow.70% of the rainwater pipeline design standards can meet the drainage requirements of 1～5 years return period rainfall.(3)The simulation results of surface water accumulation showed that the depth of surface water mainly concentrated in 0.05～0.15 m,and the spatial distribution of water depth in the different recurrence periods was generally consistent.The risk of waterlogging in the whole area was mainly caused by slight water accumulation.The areas with more serious waterlogging risk were mainly concentrated at the intersection of Wu Ben Road and West Wutong Road,Siyuanhuan South Road and Fengxi Road,Qinhuang Road and Kaiyuan Road,the Kangding Road and Baimahe Road.(4)The mitigation degree of waterlogging in the study area is analyzed by increasing a certain proportion of LID measures.The results showed that: the runoff control rate is significantly improved compared with the current situation under LID mode,the overflow quantity of inspection wells is reduced by 10.66%～100%,the inundated areas of different water depth classification and flood duration are reduced by 29.38%～58.82% and 39.08%～69.31%,respectively,and the inundated areas of different levels of waterlogging risk are reduced by28.59%～59% 52%,the results show that LID measures have a good control effect on urban waterlogging,but the effect of LID measures will decrease with the increase of rainfall return period.(5)According to the simulation results and the detailed investigation of waterlogging pond points,the main causes of waterlogging in the study area include frequent extreme weather,urban development and construction,limited drainage capacity of pipe network and improper infrastructure management.Meanwhile,in view of the existing problems,this paper puts forward the solutions to the flood disaster,to enhance the overall flood prevention ability of the city. |
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