Study

Restoration success of backfilling canals in coastal Louisiana marshes

  • Published source details Baustian J.J. & Turner R.E. (2006) Restoration success of backfilling canals in coastal Louisiana marshes. Restoration Ecology, 14, 636-644.

Actions

This study is summarised as evidence for the following.

Action Category

Backfill canals or trenches: freshwater marshes

Action Link
Marsh and Swamp Conservation

Backfill canals or trenches: brackish/salt marshes

Action Link
Marsh and Swamp Conservation
  1. Backfill canals or trenches: freshwater marshes

    A replicated study in 2000–2004 of five backfilled canals in freshwater marshes in Louisiana, USA (Baustian & Turner 2006) reported that they all developed some coverage of marsh vegetation, but mainly alongside rather than within the channels. Between 20 and 25 years after backfilling, emergent marsh vegetation coverage was 80% in former spoil areas alongside the channels, on average (range 5–95% for individual canals) but only 5% within the channels, on average (range 0–55% for individual canals). The study suggests that marsh vegetation coverage on spoil banks was related to how much of the spoil bank was actually levelled to marsh elevations. Methods: The area of marsh vegetation alongside and within five freshwater canals was estimated from aerial photographs and field surveys in 2000 and 2004. The canals, originally dug by the oil and gas industry, had been backfilled with adjacent spoil between 1979 and 1984. Between 5 and 100% of the spoil heaps alongside each canal were levelled, and the canals were made shallower (but not filled completely). Some canals were plugged at one end with earth or shell dams. Four canals in this study were also studied in (1).

    (Summarised by: Nigel Taylor)

  2. Backfill canals or trenches: brackish/salt marshes

    A replicated, site comparison study in 2000–2004 of 30 backfilled canals of varying salinity in Louisiana, USA (Baustian & Turner 2006) reported that they all developed some coverage of marsh vegetation after 20–25 years, but found that they had higher plant species richness than adjacent natural marsh. Considering only the 25 brackish and saline canals, emergent marsh vegetation coverage was 65% in former spoil areas alongside the channels, on average (range 5–95% for individual canals) but only 1% within the channels, on average (range 0–100% for individual canals). The study suggests that marsh vegetation coverage on spoil banks was related to how much of the spoil bank was actually levelled to marsh elevations. For 22 canals of varying salinity (but mostly brackish or saline), plant species richness was greater alongside backfilled canals (11 species/6 m2) than in nearby natural marsh (6 species/6 m2). Remnant spoil banks supported some upland species. Methods: The area of marsh vegetation alongside and within 30 canals was estimated from aerial photographs and field surveys in 2000 and 2004. Plant species were recorded alongside 22 canals (six 1-m2 quadrats/canal) and in nearby natural marsh (six 1-m2 quadrats/site). The canals, originally dug by the oil and gas industry, had been backfilled with adjacent spoil between 1979 and 1984. Between 5 and 100% of the spoil heaps alongside each canal were levelled, and the canals were made shallower (but not filled completely). Some canals were plugged at one end with earth or shell dams. This study selected canals from the same master set of 33 used in (1) and (3).

    (Summarised by: Nigel Taylor)

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