Comprehensive Evaluation Method For Urban Flood Warning In Zhengzhou

Urbanization is one of the powerful factors that cause the change of the natural environment.The process of urbanization increases the interaction between human society and the environment.With the development of the city,the runoff generation mechanism caused by the changed city underlying surface change into artificial materials with cement and asphalt waterproof ability.The natural flow concentration path has been changed when the building density and impervious surface increased.In the same time,the confluence of slope hydraulic condition has been changed in accordance with the bus pipeline,the slope of combining form into the river and other process of city area changed.Thus,the hydrograph in city area are higher and thinner than before,and more drainage pressure for the city and downstream are increased.It is important that the forecasting accuracy in simulating storm-flood process are enhanced.The storm flood management model of Zhengzhou city was set up based on analyzing the characteristics of runoff generation of the storm water management model(SWMM)in accordance with the underlying surface runoff and drainage characteristics of the study area network.Storm-flood model was built for different concentration unit in the study area.The concentration unit were reconmended in the drainage network and underlying condition.The fuzzy comprehensive evaluation method are used to evaluate the storm-flood grade of the Zhengzhou city based on the selected evaluated indices.The main research contents and results are as follows:(1)The studied content were identified when I summarized the research status of the storm-flood forecasting in the city.The technologic route for the study were established.(2)The storm-flood forecasting model were established based on the SWMM model according to the Zhengzhou city status which the function of data handling and space analysis in GIS was used to draw the average slope and impervious.The drainage network was generalized with the space topology relationship of thenetwork.(3)The concentration units were divided according to the topography,drainage network and draining rainwater handy.The storm-flood models which the average area of concentration unit are 0.09km2,0.16km2,0.25km2,0.36km2,0.64km2 and 1km2were set up,respectively.The models were simulated by used different return period and observed precipitation.The results showed that there are closed relationship between the concentration unit and water hazard.The number of concentration unit area is 2200(the average area 0.25km2)grid simulation water points closer to measured water points through the simulation of the actual rainfall with the networks and underflying conditions.,(4)Four indices of 3h cumulative rainfall,submergence deep,waterlogging disaster degree and comprehensive management efficiency for waterlogging were selected as the evaluation index based on the DPSIR(driving forces?pressure?state?impact?response)model.The index weight was determined by using the AHP method.Storm-flood forecasting degree of the study area were evaluated used the fuzzy comprehensive evaluation method.The results showed that level 1 warning will be started in Zhengzhou when the designed rainfall return period exceeds the five-year term.Thus,Zhengzhou will be faced with waterlogging disaster at different levels.