Research led by Deltares, USGS, and USACE investigates the interplay between tropical and extratropical cyclones in driving coastal flooding along the subtropical Southeast Atlantic Coast of the United States. The research presents a comprehensive flood hazard and impact assessment spanning from Virginia to Florida, offering critical insights into the region's vulnerability to flooding events.

Coastal communities along subtropical coastlines are frequently impacted by both tropical cyclones (hurricanes or tropical storms) and extratropical cyclones (winter storms or typical low-pressure areas). Accurately discerning the relative contributions of these distinct weather phenomena to coastal flooding has long remained a challenge for scientists and policymakers.

In the study, physics-based hydrodynamic modeling skillfully reproduces coastal water levels based on a comprehensive validation of tides, almost two hundred historical storms, and an in-depth hindcast of Hurricane Florence.

Key findings reveal a detailed picture of flood risk distribution across the region. While extratropical cyclones were twice as likely to trigger yearly flood impacts, tropical cyclones emerged as the dominant force during rarer 100-year events, contributing to over half of the regional flood risk.

As sea levels continue to rise, exacerbating the threat of coastal inundation, the study underscores the inevitability of increased flooding across the Southeast Atlantic Coast, regardless of cyclone type. In particular, densely populated counties such as Miami-Dade and Broward are characterized by heightened flood risk, but the study also identifies flood vulnerability in several less populous counties, where the relative risk of flooding was disproportionately high.

The study “Tropical or extratropical cyclones: what drives the compound flood hazard, impact, and risk for the United States Southeast Atlantic coast?” was published in Natural Hazards.