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Storm-Induced Coastal Change |
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Storm-Induced Coastal Change
Inundation and Island Breaching
Inundation occurs when an island is completely submerged under the rising storm surge. Inundation may occur on a large scale, covering an entire island, or it may be localized to a small region of the coastline. Inundation is most likely to occur on an island that is naturally low in elevation (Fig. 1), although it may also be triggered by the severe erosion and overwash of the coastal dune system. During the period of inundation, currents and waves carry large volumes of sand from the seaward to the landward side of the island. When water levels subside, currents may reverse direction carrying sediment from sounds and bays back to the open ocean. These strong currents may carve a channel in the island, causing the island to be bisected in a process known as island breaching (Fig. 2). Breaches can vary in width from several kilometers to tens of meters (Fig. 3). Smaller breaches often fill with sand in the months following the storm, while larger breaches may become permanent inlets.
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