Study On Comprehensive Performance Evaluation System Of Sponge City LID Measures Based On FCE

The rapid development of economy has continuously raised the urbanization,with the permeable surface area decreased constantly,resulting in weakness of underlying surface on interception and infiltration capacity,loss of rainfall resources and increasing of urban flooding risk.In the context of sponge city construction,taking the newly-built area(located in Xixian new area,Fengxi new city)and built-up area(Located in Xi'an,Chanhe basin)as the objects,urban hydrologic,hydraulic and environmental effects of different layout conditions for LID measures in newly-built area and optimization schemes of different drainage systems in built-up area were studied combined with field monitoring,model simulation and comprehensive evaluation methods.The following conclusions are drawn:(1)The S WMM models of newly-built and built-up area were established for revealing urban hydrologic,hydraulic and environmental effects under different recurrence periods.With the increasing of recurrence periods,the parameters such as runoff coefficient,runoff and load reduction rates were increased and the amplification gradually decreased when the rainfall duration was a certain value.In process of rainfall scouring,the pollutant amount washed out by high intensity rainfall was close to the maximum cumulative amount,the scour amount tended to be saturated,and the increase of peak concentration decreased.In the later attenuation process,the larger the recurrence period was,the shorter the time reached the stable concentration and the smaller the stable concentration was.(2)The influences of different recurrence periods and different layout conditions for LID measures(Different combinations,locations and areas)on the rainfall runoff and non-point source load were simulated and quantified.Scheme 1(rain garden+permeable pavement+green roof)had the best effect of runoff and pollution load reduction,in which rain garden was the most effective single measure on runoff and pollution load.When LID measures were placed downstream of the drainage system,,the reduction effects of runoff and pollution load was the best.When the LID measure layout area was 20%of the newly-built area,the effects of runoff water and pollution load reduction was the best,but which would not change when the area increased to a certain extent.(3)The influences of different recurrence periods and different retrofit scheme(Enlarge pipe diameter,add LID measures and combine the two)on the rainfall runoff and non-point source load were simulated and quantified.The effects of runoff coefficient,runoff and pollution load reduction of each scheme were ranked as:scheme 3>scheme 2>scheme 1.Both enlarging the pipe diameter and adding LID measures could reduce overflow,so that more water could be discharged through pipe network.LID measures had a good effect on rainfall runoff interception,storage and reduction.Increasing the pipe diameter haD almost no effect on the pollution load reduction,while adding LID measures can obviously improve the pollution load reduction effect.(4)Based on the fuzzy evaluation(FCE)method,the comprehensive performance of LID measures under different layout conditions in the newly-built area was comprehensively evaluated.Under different LID measure combination conditions,each scheme were affiliated with ?.The score and comprehensive efficiency of scheme 4(green roof+permeable pavement+vegetative swale)were the highest.The order of comprehensive performance of each single LID measure was:permeable pavement>green roof>vegetative swale>rain garden.Under different LID measure location conditions,each scheme were affiliated with V.When LID measures were arranged downstream of drainage system,the comprehensive score and efficiency were the highest.Under different LID measure area conditions,each scheme were affiliated with V.When the layout area of LID measures was 20%,the comprehensive score and efficiency were the highest.In the sponge construction,priority should be given to the combination of different measures.Secondly,,LID measures should be laid out as many as possible under land conditions and standards,and LID measures should be placed close to the downstream of the drainage system.(5)Based on FCE method,the comprehensive performance of different retrofit scheme in built-up areas was comprehensively evaluated.The score and comprehensive efficiency of scheme 1(Enlarge pipe diameter)were the highest.In the reconstruction of drainage system in built-up areas,priority should be given to increasing rainwater pipe diameter,and then LID measures should be added to the available land.