Abstract The magnitude of floods depends not only on the intensity and pattern of precipitation during the flood event (the ‘flood-producing’ precipitation), but also on the moisture stored in the catchment, which arises from antecedent hydrological processes over many preceding timescales. To characterise this effect, an empirical study is conducted on the influence of antecedent precipitation on significant flood events across multiple climate zones and catchment conditions, using 100 Australian catchments with hourly streamflow and precipitation. Antecedent conditions are shown to have a significant influence on flood volume, with three quarters of catchments having at least a 50% difference in flood volume depending on whether the catchment is wet or dry before the flood-producing precipitation event. The study considers the sensitivity of flow to antecedent precipitation by means of an ‘elasticity’ metric, which indicates the proportional change in flow for a change in antecedent precipitation or flood-producing precipitation. Flood-producing precipitation nevertheless remains the dominant flood driver across most catchments, with the elasticity of flow to antecedent precipitation typically being between 28% and 37% of the elasticity to flood-producing precipitation. Importantly, the elasticity of flow to antecedent precipitation relative to flood-producing precipitation decreases with increasing event magnitude, highlighting that conclusions of future change based on annual maximum streamflow may not be reflective of the processes that operate for more extreme floods that have the greatest impact on society.

中文翻译：

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前期降水对洪水量影响的实证研究

摘要 洪水的规模不仅取决于洪水事件（“引发洪水”的降水）期间降水的强度和模式，还取决于流域中储存的水分，这是由许多先前时间尺度的先行水文过程产生的。为了表征这种影响，使用 100 个澳大利亚集水区每小时的流量和降水，对前期降水对跨多个气候区和集水区条件的重大洪水事件的影响进行了实证研究。先前的条件对洪水量有显着影响，四分之三的流域洪水量至少有 50% 的差异，这取决于在产生洪水的降水事件之前流域是潮湿还是干燥。该研究通过“弹性”度量来考虑流量对前期降水的敏感性，该指标表明流量随前期降水或洪水产生的变化而发生的比例变化。尽管如此，洪水产生的降水仍然是大多数流域的主要洪水驱动因素，流量对前期降水的弹性通常介于洪水产生降水弹性的 28% 到 37% 之间。重要的是，相对于产生洪水的降水，流量对前期降水的弹性随着事件强度的增加而降低，这突出表明基于年度最大流量的未来变化结论可能无法反映影响最大的更极端洪水的运行过程在社会上。