On the role of the runoff coefficient in the mapping of rainfall to flood return periods
On the role of the runoff coefficient in the mapping of rainfall to flood return periods
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DOI：
10.5194/hess-13-577-2009
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发表时间：
2009-05
影响因子：
6.3
通讯作者：
A. Viglione;R. Merz;G. Blöschl
中科院分区：
文献类型：
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作者：
A. Viglione;R. Merz;G. Blöschl
虽然降雨重现期TP和洪水重现期TQ的对应关系是设计暴雨过程的核心，但它们之间的关系仍然知之甚少。本文的目的是阐明对这一关系的控制，特别是考察事件径流系数的变异性的影响。假定了一个考虑块状降雨和线性集水区响应的简化世界，并在解析模式和蒙特卡罗模式下使用了导出的洪水频率方法。结果表明，TQ可远高于与之相关的风暴的TP。Tq/Tp的比值取决于体系的平均湿度。在干燥的体系中，TQ可以是TP的数百倍。相反，在潮湿的系统中，洪水的最大返回期永远不会超过相应风暴的几倍。这是因为潮湿的系统不可能比正常情况糟糕得多。与雨量相关的径流产生的门限效应的存在降低了TQ/TP的最大值，因为它降低了径流系数的随机性，增加了处于潮湿状态的可能性。文中还讨论了采用预选径流系数时，设计暴雨过程的输入和输出的重现期之间的关系，以及径流系数产生的洪水重现期等于降雨重现期的问题。对于这里分析的系统，这个径流系数总是大于引起最大年洪水的径流系数的中位数。它取决于系统的平均湿度和所考虑的重现期，当存在径流产生的阈值效应时，它的变异性特别大。
While the correspondence of rainfall return period TP and flood return period TQ is at the heart of the design storm procedure, their relationship is still poorly understood. The purpose of this paper is to shed light on the controls on this relationship examining in particular the effect of the vari- ability of event runoff coefficients. A simplified world with block rainfall and linear catchment response is assumed and a derived flood frequency approach, both in analytical and Monte-Carlo modes, is used. The results indicate that TQ can be much higher than TP of the associated storm. The ratio TQ/TP depends on the average wetness of the system. In a dry system, TQ can be of the order of hundreds of times of TP . In contrast, in a wet system, the maximum flood re- turn period is never more than a few times that of the cor- responding storm. This is because a wet system cannot be much worse than it normally is. The presence of a threshold effect in runoff generation related to storm volume reduces the maximum ratio of TQ/TP since it decreases the random- ness of the runoff coefficients and increases the probability to be in a wet situation. We also examine the relation be- tween the return periods of the input and the output of the design storm procedure when using a pre-selected runoff co- efficient and the question which runoff coefficients produce a flood return period equal to the rainfall return period. For the systems analysed here, this runoff coefficient is always larger than the median of the runoff coefficients that cause the maximum annual floods. It depends on the average wet- ness of the system and on the return period considered, and its variability is particularly high when a threshold effect in runoff generation is present.