| Aerial Growth of the Sabine Terracing Project Over a Ten year Period |
PRESENTATION
Bill Good, Hampton Peele and Reed Bourgeois
Louisiana Geological Survey
Louisiana State University
3027 Energy, Coast & Environment Bldg.
Baton Rouge, LA 70803
Abstract
Terracing is a fairly new restoration technique in which a series of ridges are constructed to marsh elevation in shallow coastal ponds or bay bottoms. The first such project was built at the Sabine National Wildlife Refuge in Cameron Parish, Louisiana in 1991. By the end of 2005, at least 18 additional terrace projects will have been constructed across coastal Louisiana. A brief overview of these projects will be provided, including locations, descriptions and images. Even at this preliminary stage, a comparison of these projects suggests that two key determinants of terrace stability are the ambient wave-energy regime and terrace size. Other factors are also assumed to be important, but additional comparative data needs to be assembled and analyzed, such as terrace soil conditions, the underlying substrate's foundation properties, terrace side-slope steepness, water depths, density of submerged-aquatic vegetation, and presence or absence of vegetation in the intertidal reach of the terrace shoreline.
A more in-depth overview of the Sabine 1991 project will be provided. A GIS analysis of aerial imagery spanning 13 years will be presented to illustrate the spatial dynamics of the terraces and of the adjacent pond edges. This analysis indicates that sediment has accumulated sufficiently in the vicinity of the terrace fields to result in a substantial enlargement of many of the terraces and encroachment of some of the adjacent shorelines into areas which were formerly open water. Proximity to sediment supply appears to be a key factor in the observed amount of terrace and adjacent pond-edge expansion. |
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