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Barrier Islands—Habitat of the Month

The term barrier islands might conjure images of beaches, boardwalks, and vacation homes for some, but barrier islands function as more than just areas for tourism and recreation. As the first line of defense during storms that threaten coastal communities, barrier islands are very important for reducing the devastating effects of wind and waves and for absorbing storm energy. They are also important marine habitat that supports commercially important fish species, as well as birds, sea turtles and other wildlife species.

Barrier Island Habitat Zones

Barrier islands are long, narrow, offshore deposits of sand or sediment that run parallel to the coastline. They are separated from the main land by a shallow sound, bay, or lagoon and are often found in chains along the East Coast and Gulf of Mexico. The islands themselves are separated by narrow tidal inlets.

A barrier island is made up of the following habitat zones:

  • Salt marsh—Low-lying area on the sound-side of a barrier island that is stabilized by cord grasses and flooded by daily tidal activity. Helps purify runoff from main land streams and rivers.
  • Barrier flat (overwash)—Formed by sediment pushed through the dunes by storms and stabilized by grasses. Often flooded daily during high tide.
  • Dunes—Sand carried and deposited by winds and stabilized naturally by plants and sometimes artificially by fencing. Can be flooded during storms.
  • Beach—Ocean side of the island with sand deposited by wave action. Covered by salt water twice daily.
A Typical Barrier Lsland

Barrier Island Conservation

Although NOAA is actively involved in the conservation of barrier islands along the East Coast and Gulf of Mexico, some of our largest projects are on the coast of Louisiana. Through the Coastal Wetlands Planning, Protection and Restoration Act, NOAA is partnering with the State of Louisiana to target the Barataria barrier island chain, particularly the eastern part of the island arc. This area is comprised of a broad expanse of fragile deteriorating interior marshes and open water areas. If the barrier island line is not maintained, it will lead to rapid erosion of the marsh area and merging of open water areas. This specific barrier island chain also helps protect the most inhabited portion of the Louisiana coastal zone from hurricane storm surge.

Value of Restoration

Some might question the sustainability of barrier island restoration and whether storms will just “erase” all the effects of the restoration. Recent observations after the passage of hurricanes in 2005 and 2008 illustrated that restored barrier islands weathered the storms much better than adjacent non-restored areas. While the restored portions maintained their sandy beaches, unrestored portions eroded back to a predominantly marsh shoreline. NOAA’s restoration work does extend the lives of these islands; however, their construction and maintenance is costly and made more difficult by the interruption of natural island sustainability—a result of the channelization of the Mississippi River, which reduces the ability for sediment to build the islands.