Optimization Of Technical Solution For Low Impact Development Of Sponge City Under Annual Runoff Control

The use of low impact development facilities in urban construction and transformation can effectively reduce runoff,peak flow and runoff pollution.Based on the theory of sponge city construction and the analysis of the application effect of low impact development technology,this paper completes the optimization model of low impact development in the study area,and simulates the generation of rainwater runoff and drainage of pipeline network in this area.The calculation method of annual total runoff control rate for sponge city runoff control is established,and the simulation and analysis of low impact development and construction are carried out on this basis.The main research contents and achievements are as follows:According to the three control indexes of total runoff,peak runoff and runoff pollution in sponge city construction,the characteristics and application scope of low-impact development technology,the mitigation ability of heat island effect and the effect of carbon emission reduction were constrained.A linear programming model was established to achieve the allocation and optimization of low-impact development measures in sponge city construction area with the lowest cost as the objective function.Under the optimal allocation of measures,compared with traditional development,runoff generation decreased by 48626 m~3,total TSS removal rate in runoff reached 65%,average surface temperature decreased by 5 degrees,and annual carbon dioxide emissions decreased by 1374044 kg for the three-year rain event.The control effects of runoff,peak runoff and runoff pollution in different rainfall event areas under the traditional development mode were analyzed.The calculation method of‘annual total runoff control rate'for sponge city runoff control was established.Based on the results of optimal allocation of linear programming model,a low-impact development drainage system model was established in combination with the study of regional rainwater pipe network system.The hydrological effects of drainage system under low impact development mode,under different rainfall intensities,rainfall patterns and rainfall duration were studied from four aspects:total runoff discharge of pipeline network,regional comprehensive runoff coefficient,peak discharge of drainage outlet and water quality pollution.The results of runoff control in the construction area of sponge city were compared under the conditions of total annual runoff control and expected rainfall control.It was found that total annual runoff control was more accurate but more complex.When choosing the control conditions of sponge city construction,the local natural,economic and technological conditions should be fully considered.