Southern tips of Assateague Island and Hog Island are growing today, while the northern tips are eroding away. Such sand bars are quickly eroded by wave action, with sand carried south on the Virginia coast by longshore currents. If a storm surge raises the height of water in the bay, a flood in the other direction may burst through the dune line and create an ebb-tide sand bar on the ocean side of the island. Barrier islands are widened by such flood-tide deposits, especially after saltmarsh cordgrass ( Spartina patens) extends into the new deposit and starts growing to expand the marsh, but currents and storms can simultaneously narrow barrier islands by eroding sand from the ocean side. Overwash fans develop when waves breach the dunes, carrying sand inland and depositing it at flood tide behind the dunes - sometimes covering the maritime forest or marsh with a layer of fresh sand, but often filling some of the open water in the bay/lagoon. Source: National Park Service, Cape Lookout Geologic Activityīarrier islands are constantly re-shaped by storms. A maritime forest may grow behind the dunes if the island is wide enough. These projects address damage to natural resources and wildlife from the Deepwater Horizon oil spill, but the restored barrier islands also provide added coastal resilience and protect important estuary habitats.Barrier islands are typically thin strips of sandy beaches on the ocean side, with a line of sand dunes in the middle and a salt-water marsh between the dunes and a lagoon/bay. Thousands of acres of barrier islands and marshland have been restored or enhanced as part of Gulf Spill Restoration projects. NOAA supports natural and nature-based infrastructure projects that restore and protect barrier islands and the benefits they provide to coastal communities and ecosystems. The effects of climate change, including rapid sea level rise and extreme weather events, can cause or worsen barrier island erosion. Damming and dredging projects can significantly affect the amount of sand and sediment available to fortify barrier islands. Erosion can be caused by human activities such as ship traffic, hard levees, and infrastructure projects, even those far upriver. Unfortunately, barrier islands are disappearing at an alarming rate. This generally means smaller storm surge and less flooding on the coast. Beach dunes and grasses on barrier islands absorb wave energy before the wave hits the mainland. These islands are critical to protecting coastal communities and ecosystems from extreme weather. The rocky cliffs and shifting tectonic plates off the West Coast, along with other features of the terrain and tides, prevent barrier islands from forming there. Barrier island chains tend to form near river deltas and in areas with low tectonic activity and relatively flat coastal terrain. Gulf and East coasts, such as the Outer Banks off North Carolina. Many barrier islands are found off the U.S. These areas are important habitat for seabirds, fish and shellfish, and nesting sea turtles. Beaches and sand dune systems form on the side of the island facing the ocean the side facing the shore often contains marshes, tidal flats, and maritime forests. They are generally separated from the mainland by tidal creeks, bays, and lagoons. As wind and waves shift according to weather patterns and local geographic features, these islands constantly move, erode, and grow. Barrier islands form as waves repeatedly deposit sediment parallel to the shoreline.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |