植草沟对北京市道路地表径流的调控效应

[目的]分析植草沟对北京城市道路径流的水量和水质的调控效应,为北京市雨洪管理提供参考。[方法]实地建立植草沟,并根据北京市多年降雨资料和主干道路径流水质2010—2012年的监测结果设置径流水量和水质。[结果](1)降雨历时短,降雨强度低时植草沟的调控水量的功能明显。在降雨历时为3h,降雨重现期为0.33a时,50m2的植草沟可削减50m2沥青道路上产生的66%的径流量,降雨强度相对降雨历时来说对植草沟传输入渗的影响更大。(2)植草沟对水质污染物有一定的去除效果,但达不到完全净化。建设的植草沟能够削减径流中的氨氮达20%,总磷达35%,COD达22%。(3)植被覆盖度能影响植草沟的调控能力。植被覆盖度增加60%,植草沟对0.33年重现期降雨1h的雨量入渗率提高了8%。(4)若建立与北京市城六区道路等长度、宽2m的植草沟,对1a,2a重现期24h降雨形成的道路径流削减率分别为96.3%和56.0%,但对50a极端降雨道路径流量的削减率仅为13.0%。[结论]植草沟对北京市道路地表径流具有一定的调蓄洪峰流量,延缓产流时间,减少径流污染的作用,但无法单独作为有效控制城市道路地表径流水量的管理措施。

Regulatory Effect of Grassed Swales on Road Surface Runoff in Beijing City

[Objective] To analyze the regulatory effect of grassed swales on road surface runoff in order to provide reference for managing rainfall flood in Beijing City. [Methods] The grassed swales were constructed, and the volume and quality of water flowing was designed based on the data of the average rainfall situation and water quality of road surface runoff in Beijing City recorded during 2010-2012. [Results] (1) The effect on reducing the volume of surface runoff was stronger under rain events with short durations and low intensities. When the duration of the simulated rain event was set to three hours and the return period of rainfall was set as 0.33 year, the 50 m² grassed swales can reduce 66% of the total volume of surface runoff generated from a 50 m² road section. The intensity of a rain event has stronger influence on reducing the volume of surface runoff than the duration; (2) The grassed swales could improve the water quality but could not remove the pollutants entirely. The removal rates of ammonia nitrogen, total phosphorus, and chemical oxygen demand(COD) was 20%, 35%, and 22%, respectively; (3) The vegetation cover had an impact on the effectiveness of the grassed swales. When the vegetation cover increased by 60%, the volume of infiltrated water increased by 8% for a simulated rain event with 0.33-year return period and one hour of duration. (4) If two-meter wide grassed swales can be built along all roads in the six urban districts, they can reduce the road surface runoff resulted from rain events with one-year and two-year return period in 24 hours by 96.3% and 56%, respectively. However, for extreme precipitation such as rain events with 50-year return period, the reduction of road surface runoff is only 13%. [Conclusion] The grassed swales had certain effects on reducing the peak flow, delaying the time of runoff, and improving the water quality of runoff in Beijing City, but it is not an effective management measure to control the urban road surface runoff water, when used alone.