Simulation Study On Runoff Reduction And Control Effect In Low-lying Urban Area Of Handan City Under Comprehensive Measures

With the rapid development of urbanization and modernization in China,some cities pay too much attention to the surface buildings in the process of construction,while neglecting the defects and shortcomings of pavement and underground supporting facilities are becoming increasingly prominent.High degree of city underlying surface hardening and underground drainage pipeline construction standard and scale can’t keep up with the speed of economic development,which leads to frequent flood disasters in urban areas.How to effectively carry out early warning to reduce the impact of urban floods and economic losses has become the focus and difficult problem of urban flood management.This paper expounds the necessity of this research according to the present situation of flood disaster in China.It introduces the progress of related research at home and abroad and explains the principle of surface runoff generation and concentration.Based on the MIKE FLOOD model,a 1-D and 2-D hydrodynamic coupled urban rainwater-flood model in the east of Handan is constructed.The rainfall-flood process of design rainfall under different return periods and different rainfall peak coefficients was simulated and analyzed.The influence of comprehensive improvement measures on flood routing process in the study region was compared and analyzed from different angles,and the effect of different measures on surface runoff reduction and control was evaluated.The results are shown as follows:(1)Under the designed rainfall scenarios of different return periods,the evaluation indexes of surface runoff accumulation,runoff velocity,pipe network load and river water level and discharge increase with the increase of recurrence period.(2)The time interval between rainfall peak and flood peak and the cumulative amount of surface runoff decrease with the increase of rainfall peak coefficient in different rainfall peak coefficient design scenarios.(3)After adding wetland parks,pipeline network transformation and river corridor transformation,the evaluation indexes of surface runoff accumulation,runoff velocity,pipeline filling degree and node overflow in the study region have been improved to some extent,and the effect of runoff reduction and control has been achieved.However,with the increase of design rainfall recurrence period,the improvement effect of the evaluation indexes has been gradually reduced.(4)Based on the analysis of the process of rainwater flooding on the surface and the maximum depth of surface water accumulation,it is found that the surface water accumulation in the eastern residential area and the northern low-lying area is much higher than that in other areas,and is more prone to flood disasters.On this basis,the waterlogging-prone areas are divided to provide technical support for the prevention and control of flood disasters in the future and to reduce the loss of flood disasters.The results of the study carried out a comparative analysis of the surface runoff indicators in the study region from various perspectives.At the same time,the effects of three middle-level sponge measures on the runoff reduction and control in typical low-lying urban areas were evaluated,which provided strong technical support and decision-making basis for the construction of urban flood control projects in the process of urbanization in semi-urbanized areas of northern China.