The Ramsar Convention on Wetlands

The Ramsar Convention's resources on Wetland Restoration

The STRP Expert Working Group on Wetland Restoration

Restoration Approach: Backfilling Canals

Wetland type: Marsh and swamp

Background: Canals are dredged through wetlands to allow access for navigation, petroleum extraction, hunting, and logging.  Dredged material removed from canals is usually piled along the edge of canals in spoil banks.  Vegetated habitat in the canal itself is replaced by open water habitat, while vegetated habitat along the edge of the canal is buried under spoil banks (see top photograph).  Canals may allow salt water intrusion, while spoil banks block sheetflow across the marsh, leading to substantial indirect marsh loss.  If canals are abandoned, backfilling can lead to at least partial recovery of lost marsh habitat (see bottom photograph).

Advantages: Backfilliing can lead to at least partial restoration of wetlands impacted by canal construction.

Disadvantages: It is difficult to completely removed spoil banks; material remaining is spoil banks will continue to block sheetflow across the marsh.  In older canals, especially those dredged through organic substrates, oxidation of spoil banks reduces the volume of material available for backfilling, and in many cases original elevations cannot be achieved.  Stakeholders are often reluctant to allow backfilling, even in canals that are seldom or never used.  The ability of backfilling to reverse indirect losses is unknown.

Further information: Neill, C. and R.E. Turner.  1987.  Backfilling canals to mitigate wetland dredging in Louisiana coastal marshes.  Environmental Management 11: 823-836.

A recently dredged canal in Louisiana, U.S.A. 

A backfilled canal in Louisiana, U.S.A.  After the canal was abandoned, floating dragline was used to place material from the spoil banks into the canal.  Over time, vegetation becomes established in the backfilled canal.  In this case, spoil banks were not completely removed, and trees and shrubs characteristic of higher elevations cover the high ground of remaining spoil banks.

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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.