Dominant flood generating mechanisms across the United States

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.