Backfill canals or trenches: freshwater swamps
Overall effectiveness category No evidence found (no assessment)
Number of studies: 0
Background information and definitions
Backfilling involves returning dredged or excavated material to a canal (e.g. dug for boat traffic) or trench (e.g. dug for pipelines). Sometimes additional soil or sediment is brought in if there is not enough excavated material left. In theory, backfilling restores more natural wetland conditions: the water depth in the canal and the height of adjacent spoil heaps are both reduced. The whole area then has more natural water levels and may support desirable marsh or swamp vegetation. Backfilling a canal will usually prevent boats from using it too. The success of this action may depend heavily on the skill of the operator, e.g. their ability to create the desired water/soil elevations and avoid overcompacting the fill material. Turner et al. (1994) estimated that backfilling canals in Louisiana cost US$1.20/m3 (US$1.98 corrected to 2017).
For this action, as throughout the synopsis, we have only summarized results that are solely or predominantly related to the specified habitat. For example, the results in Turner et al. (1994) combine data from approximately 80% brackish or salt marshes and 20% freshwater marshes – so they have not been summarized as evidence for freshwater marshes.
Evidence summarized for this action relates to effects on vegetation within or immediately adjacent to canals or trenches, dug as or associated with service corridors.
Related actions: Plug/dam canals or trenches; Raise water level to restore degraded swamps; Raise water level to restore/create swamps from other land uses; Fill/block ditches not associated with service corridors; Remove surface soil/sediment.
Turner R.E., Lee J.M. & Neill C. (1994) Backfilling canals to restore wetlands: empirical results in coastal Louisiana. Wetlands Ecology and Management, 3, 63–78.