都江堰市暴雨强度公式推求研究

Study on Rainstorm Intensity Formula in Dujiangyan City

暴雨强度公式是城市雨洪工程设计的主要依据,其对科学规划设计城市排水设施、提高城市排水防涝能力和降低城市内涝风险均具有重要指导意义。基于年最大值法,通过对都江堰市42年暴雨样本的统计分析,分别基于皮尔逊Ⅲ(P-Ⅲ)型频率分布曲线和耿贝尔频率分布曲线对暴雨样本进行趋势性拟合调整,并求得了暴雨强度公式中满足精度校检要求的参数值。结果表明,耿贝尔频率分布曲线拟合效果较好。应用结果表明,当降雨历时t<15 min时,采用都江堰市暴雨强度公式计算所得暴雨强度值略小于采用成都市暴雨强度公式计算所得暴雨强度值;当降雨历时t>15 min时,采用都江堰市暴雨强度公式计算所得暴雨强度值大于采用成都市暴雨强度公式计算所得暴雨强度值,且随着降雨历时的增加,相应暴雨强度值的差异变化幅度越来越大。因此,当涉及长历时降雨雨水流量计算、需要对诸如排涝及相关调蓄设施进行规划建设时,建议采用笔者推求得到的都江堰市暴雨强度公式进行计算,这将更有利于都江堰市城市防涝安全。

The rainstorm intensity formula is the main basis for urban rainstorm engineering design,which is important for scientific planning and design of urban drainage facilities,improving the ability of urban drainage and reducing the risk of urban waterlogging.Rainstorm samples of Dujiangyan for 42 years are counted and analyzed by annual maximum method.The samples are trendly fitted and adjusted by PearsonⅢ(P-Ⅲ)frequency distribution curve and Gumbel frequency distribution curve,and the parameters in the rainstorm intensity formula that meet the requirements of accuracy calibration are obtained.The results show that the fitting effect of Gumbel frequency distribution curve is better.Application results show that the rainstorm intensity value calculated by Dujiangyan rainstorm intensity formula is slightly less than that by Chengdu formula when the rainfall duration t is less than 15 min;When the rainfall duration t is greater than 15 min,one of Dujiangyan rainstorm intensity formula is greater than that of Chengdu formula.With the increase of rainfall duration,the changing range of corresponding rainstorm intensity difference is increasing.Therefore,when rainwater flow of a long rainfall period is calculated,drainage and relevant regulation and storage facilities should be planned and built,Dujiangyan rainstorm intensity formula will be suggested,which is more conducive for urban waterlogging prevention safety of Dujiangyan City.