暴雨分布对LID设施设计深度及径流削减效果的影响

Influence of rainstorm distribution on the design depth of LID and the effect of runoff reduction

目前在确定低影响开发(LID)措施的设计深度以及对径流削减能力的方法时,一般借鉴城市排水规范中的设计暴雨法,暴雨强度采用整个历时上的平均值,但其与实际暴雨分布有一定差别。针对不同暴雨分布对低影响开发措施的两个关键指标,首先分析了雨强分布对LID设施蓄水深度的影响,然后针对一定设计标准,研究了不同暴雨分布下,LID设施削减雨水径流的效果。结果表明,针对典型设计情况,暴雨分布对于LID设施蓄水设计深度影响不大,相对差别在15%左右。而针对一定设计,暴雨分布对于计算径流削减效果影响较大,在降雨分布十分不均的情况下可达21.5%,暴雨分布越不均匀差异越显著。在设计LID设施时可以采用平均雨强,但是在确定对变化显著的极端暴雨的削减效果时,不宜采用平均雨强,应尽可能采用接近实际暴雨过程的计算方法。

At present,design rainstorm method in Urban drainage code is usually used to calculate the design depth of low impact development(LID)measures and the ability to reduce runoff,adopting average rainstorm intensity in whole rainstorm duration,which differs from actual rainstorm intensity.Aimed at the two indexes LID,this paper analyzes how storm intensity make contributions to water storage design depth of LID firstly,then doing research on the result of LID cutting runoff in different rainstorm intensity,aimed at certain design criteria.The results show that the rainfall distribution has little influence on the water storage design depth of LID for typical design situations,and relative difference is about 15%.However,rainfall distribution has a great effect on calculating runoff reduction for certain designs,reduction rate can reach 21.5%in case of rainfall distribution very uneven,the more uneven the distribution of rainfall,the more remarkable the difference.Although the average rainstorm intensity can be used in designs of LID,but to use a calculation closed to actual process when determining the effect of drastic rainstorm's reduction instead of using average rainstorm.