Simulation And Optimal Regulation Of Rainwater Runoff Reduction In Green Space In The South Lake Catchment Area Of Wuhan

The rapid urban expansion brings about the increasingly serious urban waterlogging problem,which causes inconvenience to the daily life of urban residents.In recent years,the traditional idea of using grey infrastructure such as canals and pumping stations for stormwater management has changed,and the stormwater regulation and storage function of urban green space has been paid more attention.In this study,Wuhan South Lake Catchment area is selected as the research object.Based on the current situation,the planned urban pipe network system and topographic data,the SWMM rain-flood model of South Lake Catchment area is established.The rainwater flood regulation and storage situation of the catchment area is simulated and analyzed according to different rainfall events.Corresponding to 20% and 80% of the sponge green space reconstruction areas in the South Lake Catchment area,the runoff control situation in the South Lake Catchment area under different green space construction scenarios was simulated,and the appropriate green space layout strategy for the South Lake catchment area was quantitatively analyzed from two perspectives: annual runoff total control and runoff flood peak reduction.The specific results are as follows:(1)Construction of SWMM Rainwater Flood Model and Simulation of Current Situation of Runoff Control in the South Lake Catchment AreaBased on the grey-green coupling perspective,the current situation of the rainwater runoff reduction effect of green space in the South Lake Catchment area was analyzed.From the perspective of annual runoff control rate,the current overall annual runoff control rate of the South Lake catchment area is 33.32%,and there are only 21 sub-catchment areas with an area of 86.46 ha that meet the planned annual runoff control rate of 65%.The standard area accounts for 2.9% of the total area of South Lake catchment area(excluding water bodies).Combined with the spatial distribution of stormwater runoff in South Lake Catchment area,it can be seen that the pipeline pressure in the southeast and northeast of South Lake is relatively large,especially in Optics Valley area,Xiongchu Avenue of Guanshan Avenue and the southern section of Minzu Avenue.The overall performance is that the higher the green rate of sub-catchment area,the higher the runoff control rate.(2)Short term target scenario simulation and optimized regulation of green space layout in the South Lake catchment areaUnder the near-term target scenario,sponge reconstruction was carried out according to 20% of the South Lake catchment area.The results showed that some of the catchment areas reached the standard,but the whole catchment area failed to reach the planned annual runoff control target of 65%.The comprehensive simulation results show that the design of20% to 30% green plot rate in the lower concave can achieve the efficient reduction effect of stormwater runoff with a small reconstruction area.The effects of complex concave green space(with aquifer and drainage pipe)and simple concave green space(without aquifer and drainage pipe)on a single rainfall event are not different,but the performance of complex concave green space under long duration and multiple rainfall events is better.In terms of concrete implementation,it is suggested that complex The concave greenbelt construction should be carried out in sub-catchment area with green space rate less than45%,and simple The concave greenbelt construction should be carried out in subcatchment area with green space rate greater than 45%.(3)Simulation and optimization of long-term target scenarios for green space layout in the South Lake catchment areaUnder the long-term target scenario,sponge transformation was carried out in 80% of the area of South Lake Catchment area,including sponge transformation of public management and public service land,residential land area,green land and square land in the catchment area.The result showed that 20% concave green land rate + roof greening in each sub-catchment area was not up to the standard.The method of 30% lower concave green land rate plus roof greening can reach the target of 65% annual runoff control rate,which is a suitable way for the green space sponge transformation in South Lake catchment area.To further increase the sponge reconstruction area in the South Lake Catchment area,the sponge reconstruction in the whole area of the South Lake catchment area can reach the control rate of 81.25% of the total annual runoff by using the method of 30% concave green land rate + roof greening.