Study On The Optimization Of Roofs Runoff Control In Green Building

Rainwater plays a key role in adjusting and supplementing urban water resourcesand improving the ecological environment, it is an important part in the urban watercirculation system. Built-up areas are the starting point of the urban rainwater drainagesystem, ordered emissions and efficient use of rainwater plays an important role torealize rainwater utilization as resource, it determines the merits of the city’s stormwatersystem.. In recent years, with the continuous development of urbanization, the area ofthe impervious surface is increasing, the runoff cefficient is increasing, and theconcentration time is decreasing, the problems of the stormwater flood and waterpollution which the rainwater brought about are more and more prominent. Low ImpactDevelopment (LID) is based on source control, green roofs play an important role inLID, are the starting point of the green building and community.Based on the low-impact development, combined with green building andcommunity ecological planning and building needs, to research two green roffs factorssuch as soil thickness and type of soil in Shenzhen Yuxin School and select theappropriate green roof technology in Shenzhen. The main results were as follows:Increasing the soil thickness of green roof could significantly delay the time ofstormwater runoff and the time of stormwater runoff end, cut runoff peak and the totalrunoff. Increasing the soil thickness of green roof was conducive to stormwater runoffreduction. There was a positive correlation between soil thickness of green roof and therequired time of maximum soil water content, there was an inverse correlation betweensoil thickness of green roof and increasing amount of soil water content afterrainfall.Storm intensity had little effect on stormwater runoff from green roof with lagersoil thicknes. With the increase of the soil thickness of green roof, green roofstrengthened the capacity to resist the impact of heavy rains.The length of proceedingdry period had significant effect on stormwater runoff from the green roof with lagersoil thicknes. With the growth of length of proceeding dry period, green roof with lagersoil thicknes strengthened the capacity to control stormwater runoff.The green roofs with deffient soil thickness had good neutralizing ability andnitrification ability, showed release of phosphorus. As the soil thickness increasing, theneutralizing ability is better, and the green roof has better control effect on the TN andNO3-N, while the control effect on phosphorus was not significant. The loads reductionis dependent on the water volume reduction within the green roof.As the soil thickness increasing, the nitrogen, phosphorus and organics pollution loads in stormwater runoffbecome more decrease, the reduction rates become more increase.The perlite green roof could significantly delay the time of stormwater runoff andthe time of stormwater runoff end, cut runoff peak and the total runoff. The perlite greenroof was conducive to stormwater runoff reduction.The perlite green roof could increasethe required time of maximum soil water content and amount of soil water content afterrainfall.Storm intensity had little effect on stormwater runoff from the reclaimed brickgreen roof. The reclaimed brick green roof could strengthen the capacity to resist theimpact of heavy rains.There was a significantly regularity between length of proceedingdry period and stormwater runoff from the green roofs with different soil type. Thelength of proceeding dry period had significantly effect on stormwater runoff from theperlite green roof. With the growth of length of proceeding dry period, the perlite greenroof strengthened the capacity to control stormwater runoff.The green roofs with deffient soil types had good neutralizing ability andnitrification ability. The reclaimed brick green roof has better control effect on nitrogen,the TN and NO3-N pollution loads in stormwater runoff become more increase, whilethe perlite green roof has better control effect on phosphorus, the TP pollution loads instormwater runoff become more increase.The water loads reduction is dependent on the water volume reduction within thegreen roof. There was a positive correlation between soil thickness of green roof and thewater volume reduction within the green roof. Soil water content had potential capacityto characterize the he water volume reduction within the green roof. The perlite greenroof has better control effect on water volume, organics and phosphorus, while thereclaimed brick green roof has better control effect on nitrogen. So, for Shenzhen, theperlite green roof with200mm soil thickness should choose to control stormwaterrunoff and phosphorus, and the reclaimed brick green roof with200mm soil thicknessshould choose to control organics and nitrogen.The researchs of green roofs in green guilding and community have importantrealistic meanings. It will offer technological support to control and utilize green roofsstormwater runoff in green guilding and community, select the appropriate green roofsfor Shenzhen.