Barrier islands play an enormous role in mitigating ocean swells and other storm events for the water systems behind on the mainland side of the barrier island. This effectively creates a unique environment of relatively low energy, brackish water. Multiple wetland systems such as lagoons, estuaries, and/or marshes can result from such conditions depending on the surroundings. Without barrier islands, these wetlands could not exist and would be destroyed by daily ocean waves and tides as well as ocean storm events. One of the most prominent examples is that of the Louisiana barrier islands.(1)
Grand Isle is one of the many barrier islands formed as a result of the dynamic ever-changing Mississippi River. Grand Isle originated as a sandbar connected to the mainland marshes at the western end. When the Mississippi River changed to its present course 600 years ago, portions of the old delta eroded severing Grand Isle's only connection to the mainland.
The shape of Grand Isle is constantly being changed by the continual action of wind and water. Waves breaking upon the beach at an angle cause a one-way movement of sand along the shoreline. Grand Isle has had periods of critical erosion which has necessitated the construction of stone jetties at each end of the island.
In addition to the erosion effects of daily wind and water, a much more destructive force of nature has changed the island….the hurricane. One such hurricane caused the entire beach and adjacent sand dunes to be pushed back over the island, inundating the coastal highway with sand up to three feet deep.
The answers to questions #1 and #2 can be found on the information boards at GZ. The answer to #3 can be made from personal observation at or near GZ.
1. What is the process that causes the western end of the island to erode and the eastern end to build up?
2. Over the years, many hurricanes have struck the island? Which one and in what year caused the most property damage?
3. From your vantage point near GZ, name three manmade processes that have been put into place to control the effects of erosion?
Please e-mail me the answers to the following questions and await my confirmation before logging your find.
(1)Stone, G.W., and McBride, R.A., 1998, Louisiana barrier islands and their importance in wetland protection: forecasting shoreline change and subsequent response of wave climate: Journal of Coastal Research, v. 14, p. 900–915.