降雨场次划分方法对降雨控制率的影响分析

Influence of Rainfall Division Method on Capture Ratio of Rainfall

年降雨总量控制率是海绵城市建设的主要考核指标,降雨场次划分方法是影响降雨总量控制率计算的重要因素。以北京城市副中心海绵城市试点区为例,系统分析了降雨场次划分方法对降雨总量和降雨场次控制率的影响作用规律。结果表明,最小降雨间隔时间是影响降雨场次划分结果的重要因素,随着最小降雨间隔时间的增加,小量级降雨事件与邻近降雨事件进行合并,增加了中等和强降雨事件的发生频率与降雨总量;降雨场次划分方法对降雨控制率的影响程度随设计降雨量的增加而减少,且对降雨总量控制率的影响程度高于对降雨场次控制率的影响程度;与《海绵城市建设技术指南低影响开发雨水系统构建(试行)》中选取的日降雨数据相比,场次降雨数据更能反映实际的降雨特征,在最小降雨间隔时间取6 h和24 h时,日降雨数据计算得到的设计降雨量分别偏低19.81%和35.10%。因此,在实际的海绵城市规划设计和工程建设中,应收集短历时场次降雨数据用以计算设计降雨量,从而保证设计目标(径流总量控制率)与实际建设效果的一致性。

The volume capture ratio of annual rainfall is the main assessment index for the construction of sponge city, and the rainfall division method is an important factor affecting the volume capture ratio of annual rainfall. Taking the sponge city pilot area of Beijing sub-center as an example, the influence of rainfall division method on the volume capture ratio of rainfall and the event capture ratio of rainfall was systematically analyzed. It was found that the minimum interval of rainfall was an important factor affecting rainfall division results. With the increase of the minimum rainfall interval, small rainfall events were combined with adjacent rainfall events, which increased the occurrence frequency and the volume of moderate and heavy rainfall events. The influence of rainfall division method on the capture ratio of rainfall decreased with the increase of the designed rainfall volume, and its influence on the volume capture ratio of rainfall was much higher than the influence on the event capture ratio of rainfall. Compared with the daily rainfall data in Sponge City Development Technical Guide: Low Impact Development, the event data could better reflect the rainfall characteristics. When the minimum intervals of rainfall were 6 h or 24 h , the designed volume of rainfall calculated by daily rainfall data decreased by 19. 81% and 35. 10% respectively. Therefore, event rainfall data should be collected to calculate the designed volume of rainfall during the design and construction of sponge city, in order to guarantee the consistency of design goal ( volume capture ratio of annual rainfall) and practical construction effect.