Optimisation Of The Scale And Pre-evaluation Of The Environmental Benefits Of Sponge Facilities On Water-prone Sites

As one of the core technologies in the construction of sponge cities,sponge facilities have multiple functions such as collecting,retaining,purifying and utilizing rainwater,which are important means to achieve sustainable urban development.However,in the actual construction process,designers find it difficult to integrate sponge facilities into the entire site due to limitations in investment and land use.Therefore,determining a reasonable scale for sponge facilities and achieving sponge transformation of water-prone sites at a fine scale has become an urgent issue to be addressed in the construction of sponge cities.Initially,this study took a water-prone site in Xi’an as an example to construct a SWMM model for the study area.Through the design of short-duration rainfall scenarios with rainfall amounts of 17.4mm and recurrence intervals of 3a,5a,and 10 a,the surface runoff and drainage capacity of the site’s drainage system were simulated.Based on the overflow of nodes and overload of pipe segments,waterlogging points on the site were identified accurately.The results showed that the drainage capacity of the existing rainwater drainage system on the site failed to meet the standard of the 5a recurrence interval,and there were five waterlogging points on the site.Subsequently,a qualitative analysis was conducted on the selection of sponge facilities for water-prone sites,taking into account factors such as the functions of sponge facilities and land use type.An optimization model was constructed with the area of sponge facilities as the decision variable,the annual total runoff control rate,the comprehensive runoff coefficient,and the area of sponge facilities as constraints,and the rainwater control volume and total cost as the objective function to quantitatively analyze the scale of sponge facilities.The optimal layout of sponge facilities was then determined based on the distribution of waterlogging points on the site.The results showed that the refined sponge facility transformation of waterlogging points on the site reduced the overflow nodes by 48.5%to 100% and the overload pipe segments by 29.3% to 65.4%.Finally,an evaluation system was established to pre-evaluate the environmental benefits of the site’s sponge facility transformation,including three major categories and seven sub-indicators: rainfall runoff control effect,surface source pollution reduction effect,and human comfort improvement effect.The results showed that the ecological environment of the site improved significantly after the transformation,but the rainfall runoff control effect and surface source pollution reduction effect of sponge facilities gradually decreased with increasing rainfall intensity.The research results on the optimization of sponge facility scale and pre-evaluation of environmental benefits for the site provide a reference for the sponge transformation of water-prone sites,and have certain theoretical significance and practical value.