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历史洪水资料起着延长经验频率曲线,减少成果误差的作用。处理历史洪水的关键,在于正确审定其流量数值及重现期.后者可根据历史文献,考证更远时期中洪水发生的情况来估定。实测系列的代表性,对曲线的外延也有影响.可与邻近的长期站的观测资料,进行比较分析。应用本逊(M.A.Benson)公式 P′=(a+[(N-a)/n]m)/(N+1)来调整实测期洪水的频率,具有很大偶然性.因 P′恒大于 P=m/(n+1).而实际上,P′的真值也可小于 P.不连续系列统计参数的计算,可以按 P=M/(N+1)在频率线上取样,并分组计算。也可以历史洪水及实测洪水的各自机率为权数,进行加权计算.应用克里茨基-明克里公式时,需注意 n 年系列的代表性,及 N,a,n 间应有一定的关系.
Historical flood data serve to extend the empirical frequency curve and reduce the error of results. The key to dealing with historical floods lies in the correct validation of their numerical values and their reproducibility, which can be assessed on the basis of historical documents and research on the occurrence of floods in further ages. The representativeness of the measured series also has an influence on the extension of the curve, and can be compared with the observation data of nearby long-term stations. It is quite fortuitous to use the MABenson formula P ’= (a + [(Na) / n] m) / (N + 1) to adjust the frequency of floods during the survey period since P’ is always greater than P = m / (n + 1). In fact, the true value of P ’can also be less than P. The calculation of the discontinuous series of statistical parameters can be performed on the frequency line by P = M / (N + 1) and grouped. We can also calculate the respective probabilities of historical flood and measured flood as weights, and when using Kritzky-Mekry formula, we should pay attention to the representativeness of n-year series, and there should be some between N, a, n relationship.