LID Facilities For The Analysis And Research Of The Rainwater Utilization In The Residential Area

With the development of social civilization,the pace of urbanization is getting faster and faster.Due to the increase of impervious area,it is difficult for rainwater to rapidly infiltrate,so that the speed of runoff collection is quickening,traffic volume is increased,and the emergence time of flood peak is ahead of schedule,which increases the catastrophic nature of flood.Cities are faced with many problems like runoff pollution,frequent waterlogging,and shortage of water resources;Based on the literature review of low impact development technology at home and abroad,taking a building community in Xi'an as the research object,the SWMM model is used to generalize the rainwater pipe and rainwater well into SWMM model,and build low impact development facilities in the district simulation:(1)Green plants are added to the roof of the building to create green roofs;(2)Reduce the height of the small garden in front of the building,and simulate the concave green space;(3)Using permeable concrete instead of the pavement;(4)pervious bricks are laid in the parking lot on the ground to increase the amount of infiltration of rainwater.Establishing the model of with or without LID facilities to compare the differencies with no LID facilities single LIDfacilities and four LID facilities.Meanwhile,Analysing the differences of three different situations for rainwater collection and utilization and water quality.The relationship between the runoff,the runoff coefficient and the infiltration capacity of the four rainstorm recurrence periods is obtained.The results of the study are showed that:(1)The difference between system runoff:When the LID facilities were not added,four kinds of rainstorm recurrence period(P=1a,2a,5a,10a),and the value of system runoff were 33.73 LPS,49.51 LPS,73.91 LPS,105.22LPS;After set the facilityof green roof,the runoff of the system is 17.88 LPS,25.92 LPS,38.87 LPS and 55.7LPS,and the reduction rate of the runoff is 46.99%,47.64%,47.41% and 47.06%;Under the condition of concave green roofs,the runoff reduction rates are 0.21%,1.37%,1.81%and 2.61%;When the permeable pavement was installed,t the runoff reduction rates were 53.42%,53.22%,52.65% and 51.56%;When the three LID facilities were arranged at the same time,the runoff reduction rates were 80.13%,80.36%,80.04%and 79.54%;(2)the difference between the infiltration quantity: When the LID facilities were not added,four kinds of rainstorm recurrence period(P=1a,2a,5a,10a),The value of the system permeability is 1.51 LPS,2.03 LPS,2.74 LPS and 3.23LPS;Under the condition of concave green roofs,the increasing rate of infiltration is 5.3%,5.42%,5.45% and 5.02%;When the permeable pavement was installed,the increase rate of infiltration rate was 47.02%,42.86%,39.05% and 37.77%;When the three LID facilities were arranged at the same time,the increasing rate of infiltration rate was80.13%,80.36%,80.04% and 79.54%;(3)the difference between the runoff coefficient : When the LID facilities were not added,four kinds of rainstorm recurrence period(P=1a,2a,5a,10a),The runoff coefficient of each sub catchment area of 0.6,0.65,0.7 in volatility,near 0.75;Under the conditions of green roof,lower concave green space and permeable paving,the runoff coefficient of the corresponding area in the model is obviously reduced;Three kinds of low impact development facilities set,four kinds of four kinds of rainfall return period rainfall return period(P=1a,2a,5a,10a),the runoff coefficient sub catchment areas in0.08,0.09,down 0.11,near 0.12.(4)the difference in the water quality: for the SS,the reduction rate of the concave green space is the highest,up to 60%,and the green roof has the lowest reduction rate to the SS,about 20%;For the pollutant COD,the green roof and the lower concave green space are all obvious,all of which are more than 60%,and the water permeable paving to reduce the level of COD is about 30%;For pollutants TN,concave green space has the highest reduction effect,up to 60%,followed by green roof,and the effect of permeable pavement is the least obvious;The reduction rate of the pollutant TP was67%,65% and 20% respectively in the lower concave green space,green roof andpervious pavement,and the effect of reducing the concentration of pollutants in the lower concave green space was outstanding;To sum up,LID facilities play a prominent role in reducing flood peak,reducing flood and waterlogging,reducing pollutants and relieving water pressure.