Full document / COSOC-W-86-002 - the National Sea Grant Library

Estuarineand Coastal Management- Toob ofthe
Trade. Proceedings of the TenthNationalConference
of The Coastal Society. October 12-15.1986. New
Orleans.LA. Copyrightby TheCoastalSociety
1987.
Introduction
RELATIVE SEA LEVEL RISE AND SUBSIDENCE
MEASUREMENTS IN THE GULF OF MEXICO BASED
ON NATIONAL OCEAN SURVEY TIDE GAUGE RECORDS
SheaPenland, Karen Ramsey,andRandy A. McBride
LouisianaGeological Survey
University Station, Box G
Baton Rouge. LA 70893
Coastal erosion in Louisiana
Louisiana is experiencing the most severe land loss and barrier island
erosion problem In the United States (Fig. 1). Land loss rates in the
Mississippi River delta plain exceed 102 km2 per year (Gagliano et al.
1981). Louisiana experienced a decrease in total barrier island area of
about 37 percent, from 92.4 km2 to 57.8 km2 between 1680 and 1979 (Penland
and Boyd, 1981, 1982). Current predictions indicate the entire
Plaquemines Parish delta plain will be converted into open water within
52 years, based on a land loss rate of 35.73 km2 per year and that the
entire Terrebonne delta plain will be converted into open water within
102 years, based on a land loss rate of 27.7 km2 per year (Gagliano et
al., 1981). Between 1887 and 1979, the Terrebonne Parish barrier
islands decreased in area from 48.3 km2 to 18.3 km2. At a rate of 0.326
km2 these islands will be converted to submerged sand shoals in 56 years
(Penland and Boyd, 1981; Fig. 2). Rapid relative sea level rise induced
by delta plain subsidence and combined with a deficit of terrigenous
wetland sedimentation are the primary factors driving the rapid deteri
oration of the Louisiana coastal zone.
Previous sea level rise studies
Previous Investigations have documented that the analysis of tide gauge
records is a valid technique for measuring relative sea level rise and
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