The Optimisation Method Of The Storm Water Management System In The River Network And High Density Build-up Region

With the process of urbanization,the hydrological conditions of cities have changed a lot.Development may reduce the permeability of the land surface by replacing it with impermeable roofs,roads,and paved areas,and it leads to urban flooding in recent years.Meanwhile,due to the increasing number of urban population density and factory,more and more sediment and pollution accumulate during dry period.Those sediment and pollution are eroded by first flush runoff and then transported into rainwater pipe network,finally discharged into river courses.So the first flush runoff pollution problems are aroused general concern.The article takes Lingang Logistics Park,Shanghai as the object of the research,does simulation analysis of the study area with the software Infoworks ICM.In order to solve the problems of urban flooding and first flush runoff pollution,it takes measures in source,midway and terminal period of the rainwater route.For the source treatment,the LID facilities bio-retention system,green roof and permeable pavement are chosen with the consideration of actual situation.According to the different area of each facility,three schemes are proposed and studied for optimal selection.LID facilities absorb and infiltrate rainwater at its source,the vegetation layer and soil microorganism purify and treat the runoff pollution.During the midway,intercepting well is taken into consideration to decrease first flush runoff pollution.The intercepted runoff goes into sewer network and finally is transported into wastewater treatment plant,the un-intercepted runoff are transported to rainwater storage tank.In the article,a method is proposed to calculate first flush runoff intercepted amount based on the diameter of downstream sewer pipe.At last,the volume of rainwater storage tank will be confirmed.It is related to runoff coefficient and intercepted amount of the study area.In the article,the reduction rate of each pollutant is confirmed.By modifying the intercepted amount,the appropriate value of the intercepted amount will be got.