The Ramsar Convention's resources on Wetland Restoration

The STRP Expert Working Group on Wetland Restoration

Restoration Approach: Terracing

Wetland type: Marshes in subsiding deltas

Background: In subsiding deltas, marshes are converted to open bay bottom as elevations become lower, allowing prolonged inundation of vegetation and subsequently leading to plant death.  If sediment deposition rates can be increased to a point at which sedimentation can outpace subsidence, marsh vegetation can become re-established.  In terracing, linear mounds of dredged material are constructed, some times in a checkerboard pattern.  The intent of terracing is to provide patches of quiescent water that will allow sediment deposition.  If sediment deposition rates do not increase sufficiently to outpace
subsidence, lower turbidity within terrace cells may still support submerged aquatic vegetation.

Advantages: In some circumstances, terracing may lead to recovery of vegetated emergent marsh habitat or establishment of submerged aquatic vegetation within terrace cells.  Even if this does not occur, linear mounds of dredged material provide marsh "edge" habitat, believed to be more important than open bay bottom to fish and crustaceans.

Disadvantages: The oldest terraced site in Louisiana, in Sabine National Wildlife Refuge, shows no clear evidence of increased elevation or support of submerged aquatic vegetation, suggesting that the method is not working as intended at this site.

Further information:  

  A terraced site in Sabine National Wildlife  Refuge, Louisiana, U.S.A. Although the site is almost ten years old, there is no evidence that terrace cells are filling in or supporting submerged aquatic vegetation. However, terrace cell walls appear to provide important "edge" habitat. 

Terrace cell walls, or terrace mounds, in Sabine National Wildlife Refuge, Louisiana, U.S.A.   A terraced site in Sabine National Wildlife 

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For further information about the Ramsar Convention on Wetlands, please contact the Ramsar Convention Bureau, Rue Mauverney 28, CH-1196 Gland, Switzerland (tel +41 22 999 0170, fax +41 22 999 0169, e-mail ). Posted 8 January 2001, updated 15 February 2002, Bill Streever and Dwight Peck.