Dauphin Island’s Contribution to Mississippi Barrier Islands
Often overlooked is the important and essential contribution that
Dauphin Island makes to the four downdrift barrier islands in
Mississippi (Petit Bois Island, Horn Island, Ship Island and Cat
Island). Dauphin Island serves as the pathway for the westward sand
movement to which all of the Mississippi barrier islands owe their
existence and continued health.
The remnant higher elevation dunes and cores that decreasingly
characterize the individual barrier islands provide evidence that sand
supply was abundant in the geologic past1.
However, conditions of surplus sands no longer exist and the present
sand deficit is causing the barrier islands to erode.
The loss rates of island land over the last 150 years are substantially
greater than for the previous several thousand years. This information
indicates the land loss rates have become accelerated in recent times.
The major mechanism contributing to the loss of land is attributed to
unequal updrift erosion and downdrift deposition. In other words, more
sand is being eroded updrift than is being deposited downdrift.
A second mechanism affecting the loss rates is island narrowing. The
diminished state of the narrow portions of the islands like Dauphin
Island’s West End make these areas especially vulnerable to overwash and
breaching during storms and the resulting loss of sand from the island
The Mississippi barrier islands are uninhabited, owned by the federal
government, and included in the Gulf Islands National Seashore that is
managed by the U.S. National Park Service (NPS). Dauphin Island is
the only island in this barrier island chain which is excluded from the
National Seashore designation because it is inhabited and privately
owned. Yet, from a functional standpoint, Dauphin Island provides
the same contributions to the environment as does its sister islands in
The Mississippi barrier islands were extensively altered by Hurricane
Katrina in 2005, in a manner similar to Dauphin Island. However,
since these lands are federally owned, they were recommended for
restoration in the Mississippi Coastal Improvements Program (MsCIP)
completed by the U.S. Army Corps of Engineers in 2009. An attempt
was unsuccessfully made to have Dauphin Island added to the MsCIP, due
to a lack of support within Alabama’s Congressional delegation.
(Click here to see letters submitted by various agencies, governmental
officials, and environmental organizations requesting that Dauphin
Island be added to the MsCIP.)
These letters demonstrate the wide support that was
received to correct the severe erosion issues affecting Dauphin Island.
These letters are relevant to and are supportive of the basic concept to
restore and stabilize Dauphin Island as a barrier island.
The Corps’ MsCIP report contained the following Vision Statement
prepared by the National Park Service. This statement speaks to the
historic role that Dauphin Island has played in the formation and
development of the Mississippi Sound barrier islands in saying that:
“…by ‘capturing’ the sand that arrived from the
Alabama mainland shore [i.e., the Fort Morgan Peninsula] through
current and drift processes via the Mobile Bay ebb-tidal delta and
steering it westward along its south shore, eastern Dauphin Island
probably played an important role in originally determining the
offshore position of the whole barrier island chain which extended
well into southeastern Louisiana”.
Examination of historic maps shows that Petit Bois
Island was actually created from Dauphin Island as a result of a major
hurricane around 1900 that severed the connection between these two
islands. If mapping were available for pre-European history dating
back to the last 7,000 to 10,000 years, the geologic relationship
between Dauphin Island and the other barrier islands would be clear
since the positions of all of the islands and their intervening passes
have constantly migrated to the west, with new islands being
periodically created by the effects of catastrophic hurricanes and other
islands being eroded away. The one constant variable has been the
contribution of sand to the Mississippi islands from Dauphin Island
through littoral drift processes. The delivery of sand from
Dauphin Island has always been critical to, and continues to be
essential to, determining the physical configuration and
geomorphological health of the downdrift Mississippi barrier islands.
Evidence of the significant effects that Dauphin Island’s coastal
erosion problems are having on the downdrift Mississippi barrier islands
is reflected in the MsCIP report’s recommendation to place 4,000,000
cubic yards of sand on the east end of Petit Bois Island – less than
five miles to the west of Dauphin Island. The necessity of placing sand
on the eastern end of Petit Bois Island is a direct result of the
shortage of sand that is failing to be transported to the west from an
ever-diminishing Dauphin Island.
Evidence of the importance that the U.S. Government places on restoring
the Mississippi barrier islands is the Congress’s action in 2009 to
appropriate $489 million (recent reports on National Public Radio put
the figure at over 1 billion, perhaps due to some matching funds) in
order to pump sand in the littoral zones as an extensive effort to
nourish the islands. This will take place on Mississippi’s barrier
islands while no similar action will be pursued on Dauphin Island even
though it is suffering from the same coastal erosion issues.
1 Morton (2008)