TIMBALIER ISLAND DUNE STABILIZATION PROJECT 



At this time there is only one relatively large-scale dune building and stabilization 

 project along the Louisiana coast. This project, located on a washover terrace of 

 Timbalier Island (Figure 12), is a joint effort of Texaco Corporation, U.S. Soil 

 Conservation Service, and Louisiana State University's Center for Wetland Resources. 

 The objective of this pilot project was to determine the feasibility of building and 

 stabilizing dunes along the Louisiana coast without using beach nourishment. This is an 

 important consideration since beach nourishment alone can cost from 2 million to 3 

 million dollars per linear mile of beach while dune building and stabilization via sand 

 fence and vegetation ranges from $30,000 to 60,000 per mile, 50 to 100 times less 

 expensive. In addition, any beach nourishment project will require sand fencing and 

 vegetation to keep the sand in place, thus, making the expense for the total beach 

 nourishment project even greater. 



The Timbalier Island study was initiated in May of 1981 on a 335-m long relatively 

 flat washover channel containing almost no existing vegetation (Figure 13). Sand fencing 

 was first installed to attempt to trap sand and build a small dune. Sand fencing was 

 arranged to test whether diagonal sand fencing accumulated more sand than sand fencing 

 oriented parallel to the beach. Perpendicular side spurs were also tested (Figure 14). In 

 late May, 5,000 bitter panicum transplants, thinned from populations on the Caminada- 

 Moreau barrier beach, were planted to a width of 7.6 m along this 335 m length of 

 backbeach. Percent survival of these transplants after six weeks was good and averaged 

 84%, ranging from 69% to 93%. Tillering from a single transplant after 6 months was 

 prolific with 8 to 12 new tillers originating from each original culm. 



The bitter panicum transplants were only one-third of the total number of plants to 

 be established in this area. Since a mixed planting would provide a greater potential for 

 success, two other species were also established: sea oats and seashore paspalum. 

 Because neither of these species are found in great enough abundance to be thinned from 

 natural populations in Louisiana, they were purchased from a commercial source in 

 Florida. The two species were transplanted in October and November 1981 which 

 resulted in a total of 13,200 plants spaced evenly at approximately 46-cm centers. 

 Survival rates for the seashore paspalum have been estimated at 37% after 7 months and 

 for sea oats at 28% after 6 months. 



Fertilizer was added to the transplanting site once during the first growing season 

 in late September at a rate of 227 kg of sodium nitrate and 68 kg of 0-20-20 phosphorus- 

 potassium fertilizer. 



As of this writing, a maximum of I to 1.2 m of sand has accumulated within the 

 test site depending upon the presence and orientation of the sand fencing (Figure 15). 

 The sand fencing was essential in accumulatng relatively large amounts of sand in a short 

 period. Vegetation, alone, only trapped small quantities of sand. Preliminary data 

 indicated the sand fencing with perpendicular side spurs accumulated the greatest 

 amount of sand on this beach. Bitter panicum, during the first year of this project, has 

 been the most successful of the three species planted. (Figure 16). 



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