Barrier island restoration in the Northern Gulf of Mexico: A comparison study

Background/Question/Methods

In recent years there has been an emphasis on barrier island restoration along the Northern Gulf of Mexico (NGOM), in particular on the Mississippi-Alabama barrier island chain following Hurricane Katrina in 2005.  Naturally formed East Ship Island and Disposal Area-10 (DA-10), locally known as Sand Island, offer a chance for a comparison study between a barrier island that is approximately 4,500 years old and impacted by multiple severe weather events in its evolution, to one that is roughly 30 years old.  Tentative plans call for the removal of a portion of the “man-made” Sand Island in an effort to supply sediment for the restoration of the “natural” East Ship Island.  The purpose of this study was to compare elevation, total volume, habitat type and habitat size between East Ship Island and DA-10 (Sand Island), in an effort to better understand succession in relation to island genesis, evolution, and elevation. Remotely sensed data from 2012 was used in conjunction with ground referenced data to make maximum likelihood classifications for habitat coverage on both islands.  Further, Light Detection and Ranging (LIDAR) data from 2012 was used to construct Digital Elevation Models (DEMS) for island comparisons.

Results/Conclusions

East Ship Island has a total area of 94.59ha, while Sand Island has an overall area of 58.15ha.  In a 2005 post-Katrina study, using IKONOS imagery, East Ship Island had an overall area of 46ha equating to a 105% increase in total area over seven years.  Sand Island has a total volume of 1,148,479.07m³ compared to East Ship Island’s total volume of 906,622.21m³.  Among the four common habitat types on both islands they are all similar in size with only a 5ha difference in Marsh shrubland and a 10ha difference in Beach dune herbland.  Mean elevations for all shared habitats are also similar between the two islands with a difference of only about .3m.  Similarities between these two islands are very remarkable, while their age difference is extremely different. Current plans for island restoration need to be reconsidered.  Sand Island, while technically man-made, has undergone natural processes in developing a sustainable habitat in less than 30 years in a very dynamic environment, while East Ship Island continues to show signs of natural restoration.