低洼绿地对降低城市径流深度、径流系数的效果分析

城市径流深度、径流系数取值直接影响到城市防洪排涝安全和建设投入,针对低洼绿地不同下凹深度对降低城市径流深度、径流系数的效果进行了分析。分析结果显示:径流系数受降雨量影响,当采用较高排水标准时,应当适当提高径流系数的取值;绿地不下凹时,在降雨量大的情况下,径流深度和径流系数仍较大;绿化率35%深度为100 mm的低洼绿地,在1 h不同频率降雨条件下,可以将相同径流深度所对应的降雨频率提高1～2个标准级;在1h相同频率降雨条件下,可以将径流系数降低0.3～0.4左右,显著降低汇流比例,削减洪峰流量。因此,针对目前我国部分城市防洪排涝形势严峻的情况,为有效降低城区径流深度和径流系数,有必要大力推广设置低洼绿地,绿地设置平均深度为80～120 mm为宜。

Effect Analysis of Low-lying Greenbelt to Reduce Urban Runoff Depth and Runoff Coefficient

The sampling values of urban runoff depth and runoff coefficient directly influence the safety and construction of urban flood control and waterlog drainage.The article analyzes the effect of the different concave depths of the low-lying greenbelt to reduce the urban runoff depth and the runoff coefficient.The analysis result displays that the runoff coefficient is influenced by the rainfall.The sampling value of runoff coefficient should be properly enhanced while the higher drainage standard is adopted.The runoff depth and the runoff coefficient are still greater under the condition of heavy rainfall while the Greenland has no concave.The greening rate of 35% depth is 100-mm low-lying Greenland.Under the condition of the different frequency rainfall for 1 h,the same runoff depths corresponding the rainfall frequency can be enhanced by 1~2 standard classes.Under the condition of the same frequency rainfall for 1 h,the runoff coefficient can be reduced by 0.3~0.4.It is obviously to reduce the confluence proportion and cut down the peak flood flow.Therefore,it is necessary greatly to spread the setup of low-lying greenbelt efficiently to reduce the runoff depth and runoff coefficient of area under the current condition of severe flood control and waterlog drainage in the partial cities of China.The average depth of greenbelt to set up is properly by 80~120 mm.