USGS - science for a changing world

St. Petersburg Coastal and Marine Science Center

St. Petersburg Coastal and Marine Science Center > Coastal Change Hazards: Hurricanes and Extreme Storms

Coastal Change Hazards: Hurricanes and Extreme Storms

Storm-Impact Scale

Overwash Regime

Overwash Regime
cartoon illustration of overwash regime
Net onshore transport order 100 meters
If wave runup exceeds the elevation of the dune, or in the absence of a dune, the beach berm, the system will be overtopped, transporting sand landward. This is a net change contributing to the migration of the barrier island landward.

Impacts of the Overwash Regime

Below are overwash deposits near Rodanthe, North Carolina, after Hurricane Dennis (1999). The sand was transported landward by wave runup overtopping the dune. In both photographs at right, wave runup overtopped the highest part of the system during a storm, resulting in net sand transport landward forming overwash fans.
Photograph of excavated overwash deposits left by Hurricane Dennis.
Overwash deposits near Rodanthe, NC after Hurricane Dennis (1999), which made landfall in early September 1999. Large overwash deposits were also observed following Hurricane Dennis (1999) in Buxton, NC.
photograph of overwash in North Carolina following Hurricane Dennis
September 1999, Hurricane Dennis, Core Banks, NC. [larger version]
photograph of overwash in Virginia following a strong Northeaster
February 1998, Northeaster, Assateague Island, VA. [larger version]

Refer to the Hurricane Katrina web pages, for photographs and lidar images of hurricane-induced overwash on Dauphin Island, AL.

return to Storm Impact Scale | continue to Inundation Regime


St. Petersburg Coastal and Marine Science Center > Coastal Change Hazards: Hurricanes and Extreme Storms

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo FirstGov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://coastal.er.usgs.gov/hurricanes/impact-scale/overwash.php
Page Contact Information: Feedback
Page Last Modified: April 15, 2014 01:01 PM (JSG)