Floods claim a high toll in fatalities and economic impacts. Despite
their societal relevance, there is much more to learn about the
projected changes in discharge and flooding. Here we force an
operational hydrologic model over the state of Iowa with high-resolution
convection-permitting climate-model precipitation to evaluate the
response of 140 watersheds to climate change. At the end of the century,
under the most aggressive scenario in terms of fossil fuel use, we show
that the transition from snow to rainfall and a ~30%
increase in extreme precipitation rates lead to a doubling of maximum
discharge during the spring and extended the flood season into the fall.
Total discharge volumes are also expected to increase. Our results
suggest that flood projections based on extreme precipitation increases
alone substantially underestimate future risk due to the nonlinearity of
the hydrologic response explained by long-term soil moisture memory and
its feedbacks with precipitation.