Dominant flood generating mechanisms across the United States

TLDR

River flooding has severe societal, economic, and environmental impacts, yet regional differences in flood‑generating mechanisms are poorly understood, leaving historical trends and future predictions uncertain, especially as rainfall alone fails to explain seasonal and interannual flow variability. The study systematically analyzes 420 catchments to identify the primary drivers of flooding across the contiguous United States. This analysis explores which flood‑generating processes control the seasonality and magnitude of maximum annual flows. Soil moisture‑dependent precipitation excess, snowmelt, and rain‑on‑snow events better predict flooding than rainfall alone, and the continental‑scale classification reveals timing and variability disparities that can improve flood prediction and risk assessment in the U.S.

Abstract

Abstract River flooding can have severe societal, economic, and environmental consequences. However, limited understanding of the regional differences in flood‐generating mechanisms results in poorly understood historical flood trends and uncertain predictions of future flood conditions. Through systematic data analyses of 420 catchments we expose the primary drivers of flooding across the contiguous United States. This is achieved by exploring which flood‐generating processes control the seasonality and magnitude of maximum annual flows. The regional patterns of seasonality and interannual variabilities of maximum annual flows are, in general, poorly explained by rainfall characteristics alone. For most catchments soil moisture dependent precipitation excess, snowmelt, and rain‐on‐snow events are found to be much better predictors of the flooding responses. The continental‐scale classification of dominant flood‐generating processes we generate here emphasizes the disparity in timing and variability between extreme rainfall and flooding and can assist predictions of flooding and flood risk within the continental U.S.