华南中小流域洪水频率计算方法及其对频率曲线拟合的影响

Calculation Method of Flood Frequency and Impacts on Frequency Curve Fitting of South China

针对华南地区中小流域不同经验频率计算方法引起设计洪水不确定性的问题,选取5种公式计算曹江流域、北江流域典型站点洪水经验频率,采用P-Ⅲ型分布和广义极值概率分布方法,对比不同经验公式计算点据及对分布拟合程度。结果表明,经验点据位置与所取公式的a值有关,其在不同频率内的影响相异;推荐华南中小流域洪水设计时,在低频率区间选择海森公式或Cunnane公式计算经验点据,在高频率区间选用数学期望公式;推荐采用数学期望公式作为P-Ⅲ型分布的适用公式、Cunnane为GEV分布的适用公式;典型流域洪水经验点据分布均存在跳跃现象,增加了拟合的不确定性。

Aiming at the problem of design flood uncertainty caused by different empirical frequency calculation methods in small and medium catchments in South China,five formulas were selected to calculate the flood empirical frequency of the typical stations in the Caojiang River Basin and Beijiang River Basin.The P-Ⅲtype distribution and generalized extreme probability distribution methods were used to compare the calculation points of different empirical formulas and the degrees of distribution fitting.The results show that the location of the empirical data is related to the value of the formula taken,and its influence in different frequencies is different.It is recommended to choose the Hazen formula or the Cunnane formula in the low frequency interval to calculate the empirical data in the flood design of the small and medium-sized basins in South China,and the mathematical expectation formula in the high frequency interval.The mathematical expectation formula is recommended as the applicable formula for the P-Ⅲtype distribution,and Cunnane is the applicable formula for the GEV distribution.At the same time,it is found that the distribution of flood experience points in the typical river basins has a step change,so that the uncertainty of fitting is increased.