Shifting Sands on Petit Bois Island

Dredging disrupts the natural process

As the Gulf currents continue to run from east to west, they erode the eastern end of Petit Bois Island. In the past, sand carried by currents would deposit on the western end of the island, allowing it to replenish at least some of its losses. Today, that part of the natural process is halted. Ships access the Port of Pascagoula just west of Petit Bois Island through a channel called Horn Island Pass. In order to keep that navigation channel open, the U.S. Army Corps of Engineers dredges sand out of the channel, making it deeper than it would occur naturally, and deposits the sand in other parts of the Gulf. By removing new sand that deposits in the navigation channel west of Petit Bois, sand lost from the eastern end can’t be replenished. Over time, Petit Bois Island has been shrinking.

Army Corps of Engineers recently created a sediment budget to study how much sand is lost to the barrier islands each year.

Mark R. Byrnes, et al, “Littoral Sediment Budget for the Mississippi Sound Barrier Islands“, July 2012, p. 28.
Mark R. Byrnes, et al, “Littoral Sediment Budget for the Mississippi Sound Barrier Islands“, July 2012, p. 28.

Just as with a bank account, too many withdrawals (such as through dredging) and not enough deposits (through natural replenishment in currents) will eventually deplete the island “account.”