Outwash events inhibit vegetation recovery and prolong coastal vulnerability

JGR Earth Surface
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  • Data Release: USGS data release - Supplemental data for Over and Sherwood (2025), Washover and washout locations and landcover classifications after hurricanes Florence, Dorian, Harvey, Ike, and Sandy in North Carolina, Texas, and New York
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Abstract

Overwash, when high ocean water levels and waves flood a coastline, is a common phenomenon that can lead to washover deposits and barrier rollover. Outwash, by contrast, involves seaward flow, often driven by high back-barrier water levels, and can produce washout channels and nearshore deposition. Our observations show that washout channels were quickly (days to weeks) filled and reshaped into beaches, berms, and washover deposits and ponds often formed at the landward ends. However, there was a significant delay in revegetation of former washout areas compared with washover areas. North Core Banks, North Carolina, was affected by repeat hurricanes in different ways: Hurricane Florence (2018) deposited large washover fans 0.5–1 m thick, and Hurricane Dorian (2019) removed 1–4 m of sediment from washout channels. Aerial surveys captured vegetation recolonization on the Florence washover fans within a year but, after Dorian, surveys showed that although the washout channels and ponds quickly filled with marine sand, the channel throats and new washover platforms remained mostly unvegetated for five years. New vegetation growth was associated with the washout ponds and was characteristic of low-elevation hydrophilic environments. We observed comparable outcomes at washout and washover locations on the coasts of Texas and New York and suggest that outwash interrupts the normal cycle of vegetation and dune growth that is key to rebuilding barrier islands after storms. The lack of vegetation in the former washout channels prolongs vulnerability to overwash, further delaying recovery. Our findings have implications for best-management practices and modeling of coastal geomorphic evolution.

Publication type Article
Publication Subtype Journal Article
Title Outwash events inhibit vegetation recovery and prolong coastal vulnerability
Series title JGR Earth Surface
DOI 10.1029/2024JF008162
Volume 130
Issue 6
Publication Date June 07, 2025
Year Published 2025
Language English
Publisher American Geophysical Union
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description e2024JF008162, 14 p.
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