Flash floods, largely driven by high rainfall rates in convective storms, are projected to increase in frequency and intensity in a warmer climate. This study uses high-resolution climate simulations (4-km, hourly resolution) to force a numerical hydrologic model at a continental scale, quantifying future changes in US flood flashiness. Results indicate a 7.9% increase in flashiness by the end of the century under a high-emissions scenario (RCP8.5). The Southwest shows the greatest increase (+10.5%), while the central US (+8.6%) emerges as a new flash flood hotspot. Future flash flood-prone areas are also expanding northwards, highlighting the need for climate-resilient mitigation measures in emerging hotspots.

Zhi Li, Shang Gao, Mengye Chen, Jonathan J. Gourley, Changhai Liu, Andreas F. Prein, Yang Hong