18 Mar Marsh Buggies and Duck’s Unlimited Work Together on Coastal Restoration
Ducks Unlimited contracted late last year with Marsh Buggies for the Bayou L’Ours terracing project to construct and plant 25,800 linear feet of marsh terraces. Once completed, this phase of the 4-month project will enhance approximately 250 acres of marsh habitat.
Given the crisis of coastal wetlands loss along the Gulf Coast, it is no surprise that numerous techniques have been developed and implemented to help slow this loss and return areas to more productive states. One of the more recently developed techniques is marsh terracing, which relies on the construction of linear mounds of earth from excavated subtidal substrates, which subsequently become colonized by emergent vegetation.
Terraces are most often constructed in large water bodies that were once emergent marsh but have converted to open water as a result of exposure to a variety of marsh loss factors. Terraces are usually designed with a crown height equal to surrounding marsh elevation to enable periodic tidal inundation of the terraces and associated vegetation and are often planted with native grasses to promote stabilization and decrease erosion.
Marsh terraces were conceived as a potentially effective restoration technique partly because of their ability to interrupt the negative feedback cycle of marsh erosion that is initiated once interior marshes begin to fragment. In this cycle, as intact marshes begin to fragment and convert to open water, fetch increases and enables the production of greater wave energy, which in turn increases marsh erosion rates, ultimately accelerating conversion to an ever-expanding body of open water. Marsh terraces function similarly to other restoration techniques such as breakwater and sediment retention structures to break this cycle by reducing fetch and subsequent wave energy, thereby increasing the potential for sediment deposition on the leeward side of the structure.
Terraces may be implemented to achieve one or multiple coastal restoration objectives. The primary restoration objectives include:
1. creating emergent marsh through establishment of vegetation on the terraces themselves
2. increasing marsh edge,
3. reducing turbidity to increase light penetration into the water column and promote growth of submerged aquatic vegetation SAV
4. reducing erosion of adjacent marsh by reducing fetch and wave energy, and
5. promoting the growth of emergent marsh through the gradual accumulation of sediment and subsequent colonization by emergent vegetation within the terrace field – (i.e., outside the terrace footprint).
When these objectives are achieved, terraces may benefit both fisheries and waterbird species dependent upon emergent marsh habitats.