SAND DUNE VEGETATION AND STABILIZATION IN LOUISIANA 



Irving A. Mendelssohn 



Laboratory for Wetland Soils and Sediments 



Center for Wetland Resources 



Louisiana State University 



Baton Rouge, LA 70803 



ABSTRACT 



The sandy barriers that fringe the Louisiana deltaic plain are dynamic and 

 ephemeral coastal features. In terms of development, management, and conservation, 

 these landforms pose many problems unique to the Mississippi River deltaic 

 environment. The abandonment of a major delta by the Mississippi River initiates the 

 development of a Louisiana barrier system. Nearshore marine processes and subsidence 

 become the dominant mechanisms of shoreline evolution. Marine processes erode the 

 abandoned delta and concentrate a restricted quantity of coarse-grained sediments into 

 highly mobile barrier islands, spits, and beaches which overlie unconsolidated delta silts 

 and clays. Subsidence, due to the compaction of these unconsolidated sediments, in 

 concert with a eustatic increase in sea level, generates a rapid apparent sea-level rise, 

 equivalent to I m/ 100 yr. This combination of sea-level rise and limited coastal sand 

 supply has produced the most serious barrier island erosion problem in the United States. 



The use of hard structures, such as groins, jetties, and seawalls to control or reduce 

 barrier island erosion in Louisiana has met with limited success. The use of vegetation to 

 stabilize substrates offers a sound alternative to the hard structure approach to erosion 

 abatement. This paper introduces Louisiana's barrier dune vegetation and qualitatively 

 describes the use of this vegetation for dune building and stabilization on Timbalier 

 Island, Louisiana. 



INTRODUCTION 



Critical components of many coastal systems are the low-lying strips of land called 

 barrier islands or beaches that make up the seaward boundary of the estuary and protect 

 it from the direct onslaught of the sea (Godfrey 1976). The combination of an 

 accelerated sea-level rise, due to local deltaic subsidence, and a limited coastal sand 

 supply has produced in Louisiana the most serious barrier island erosion problem in the 

 United States. Louisiana's barrier islands (Figure I) are migrating landward at rates as 

 high as 50 m/yr while losing total land area at a rate of 65 ha/yr (Mendelssohn et al. 

 1982). 



The environmental and economic consequences of shoreline erosion in Louisiana are 

 immense because of the important functions that barrier islands perform. (1) Barrier 

 islands protect marshes and create estuaries by acting as a marine buffer zone to 



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