Widespread flooding can cause major damages and substantial recovery costs. Still, estimates of how susceptible a region is to widespread flooding are largely missing mainly because of the sparseness of widespread flood events in records. The aim of this study is to assess the seasonal susceptibility of regions in the United States to widespread flooding using a stochastic streamflow generator, which enables simulating a large number of spatially consistent flood events. Furthermore, we ask which factors influence the strength of regional flood susceptibilities. We show that susceptibilities to widespread flooding vary regionally and seasonally. They are highest in regions where catchments show regimes with a strong seasonality, that is, the Pacific Northwest, the Rocky Mountains, and the Northeast. In contrast, they are low in regions where catchments are characterized by a weak seasonality and intermittent regimes such as the Great Plains. Furthermore, susceptibility is found to be the highest in winter and spring when spatial flood dependencies are strongest because of snowmelt contributions and high soil moisture availability. We conclude that regional flood susceptibilities emerge in river basins with catchments sharing similar streamflow and climatic regimes.

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在美国，洪水泛滥的可能性有多大？

洪水泛滥可能会造成重大破坏，并造成可观的恢复成本。尽管如此，主要由于记录中普遍洪水事件的稀疏性，所以仍未充分估计出该地区对普遍洪水的敏感程度。这项研究的目的是使用随机流发生器评估美国各地区对广泛洪水的季节性敏感性，这可以模拟大量空间上一致的洪水事件。此外，我们询问哪些因素会影响区域洪水敏感性。我们表明，对洪水泛滥的敏感性在区域和季节上有所不同。在流域表现强季节性的地区（即西北太平洋地区，落基山脉和东北地区），它们是最高的。相反，在集水区以季节性不佳和间歇性政权（例如大平原）为特征的地区，这些地区的水准较低。此外，由于融雪的贡献和高土壤水分的可利用性，在冬季和春季，当空间洪水依赖性最强时，敏感性最高。我们得出的结论是，流域出现了区域洪水敏感性，流域共享相似的水流和气候状况。