暴雨条件下绿化屋顶产流机制研究

摘要

绿化屋顶是减轻城市洪水灾害的一种有效手段，已被世界各国广泛使用。但是，对于绿化屋顶目前仍然缺乏一个简单的基于物理过程的模型来评价其雨洪蓄滞效果。本文首先基于水量平衡原理分析降雨量P与径流量R之间的关系，讨论绿化屋顶不同的产流机理，然后通过现场试验验证了此P-R关系。本文还使用HYDRUS-1D模拟绿化屋顶的产流机理以及评价方法的适用性。模拟结果显示绿化屋顶既会发生超渗产流，也会发生蓄满产流，但超渗产流的流量在总流量中所占比例很小。这表明虽然超渗产流存在，但之前本文提出的线性模型仍然可以用于模拟包括暴雨条件在内的绿化屋顶降雨径流关系。 Green roofs (GRs) are widely employed in urban areas to mitigate the detrimental impacts by stormwater flooding. However, a simple yet physical method for assessing the hydrological performance of GR is still lacking. In this study, we first perform an analysis on the relationship between rainfall depth P and runoff amount R based on the water balance principle and discuss the different runoff generation mechanisms on GR. A field experiment is then conducted to examine the P-R relationship constructed in the previous analysis, which demonstrates good validity in estimating runoff generated on our GR. Numeric simulations via HYDRUS-1D are then carried out to investigate the runoff generation mechanism on GR as well as to examine the applicability of the proposed assessment method. The simulation results indicate that both the saturation and infiltration excess processes occurred on our GR; nonetheless, the infiltration-excess runoff accounts for only a small portion of the total runoff. This implies that the proposed linear model is applicable for estimating the runoff from GR even under heavy rainfall condition where the infiltration-excess mecha- nism is supposedly active.