2025 CSDMS meeting-111
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Conceptual Model for Revegetation of Barrier Islands after Outwash and Overwash Events
Chris Sherwood,
U.S. Geological Survey Woods Hole Massachusetts, United States. csherwood@usgs.gov
Jin-Si Over, U.S. Geological Survey Woods Hole Massachusetts, United States. jover@usgs.gov
Extensive overwash occurred on North Core Banks during Hurricane Florence (September 2018). The washover deposits were partially revegetated when, a year later, sound-side inundation and outwash caused substantial erosion during Hurricane Dorian (September 2019). Repeat aerial mapping shows that reestablishment of vegetation on deposits that partially filled the washout channels is slow to non-existent. We suggest washout site revegetation is delayed by lack of organic material, slowing dune growth, and extending vulnerability to overwash. Washout channels often erode several meters of beach, berm, and back-barrier platform and are later filled with inorganic marine sands deposited as spits, bars, and overwash. By contrast, washover deposits can contain ripped-up vegetation and (partially) bury pre-existing vegetation, providing seeds, rhizomes, and plant fragments to generate new growth. We propose a heuristic model of vegetation growth following a sigmoidal curve that depends on an initial (seed) concentration and show that simulations with this model using realistic overwash recurrence, reproduces our observations of slow revegetation in deposits on former washout channels.
