北京地区不同设计暴雨强度下凹式绿地的减流效果

目的]研究不同汇水面积的周边外来雨水径流,计算绿地产流过程的动态径流系数以及对径流的削减率。方法]采用人工模拟的下凹式绿地,模拟绿地的不同暴雨强度。结果](1)30%下凹式绿地面积比基本可以拦蓄3年,5年一遇暴雨,稳定后径流系数在0.30以下;(2)下凹式绿地面积比为20%时,雨水口高8cm和5cm时对3年,5年一遇暴雨产生的径流削减率均在40%以上,稳定后的径流系数均在0.90以上,且两种雨水口高度下的削减率差异不明显,相比之下5cm雨水口高度设计较8cm更为合理;(3)绿地的产流速率变化过程曲线呈"几"字形,汇水面积越大、暴雨强度越大,产流速率稳定时的峰值就越大,产流历时也越长。结论]下凹式绿地对暴雨条件下产生的径流有很好的削减作用,其所占面积比越大,削减效果越好。

Runoff Reduction Effect of Sunken Lawn Under Different Designed Rainstorm Intensity in Beijing Area

Objective] This paper studied surrounding rainwater runoff of sunken lawn by calculating the dynamic runoff coefficient of runoff process and the runoff reduction rate.Methods] The sunken lawn was artificial made to simulate their occupied area proportion, and the surrounding rainwater with different intensity was simulated.Results] (1) 5 cm height designed gullies can intercept 3-year, 5-year recurred storm runoff basically when sunken lawn area ratio was 30%, and the runoff coefficients was 0.30 when it were stable; (2) When the sunken lawn area ratio was 20%, the lawn with 8 cm and 5 cm height gullies could reduce runoff rates of 3-year, 5-year recurrence storm over 40%, and the stabilized runoff coefficient was 0.90. The difference of reduction rate between the two designed gully-height lawns was not significant, and 5 cm height gullies design was more economically reasonable than the one with 8 cm gully; (3) The runoff rate from the lawn was a temporal unimodal curve. The peak flow rate was bigger and runoff duration was longer when the catchment area or the rainstorm intensity was greater.Conclusion] Runoff reduction of sunken lawn was obvious, which was greater when the area ratio was higher.