Environmental conditions of a backfilled pipeline canal four years after construction

Published source details Abernethy R.K. & Gosselink J.G. (1988) Environmental conditions of a backfilled pipeline canal four years after construction. Wetlands, 109-121.
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This study is summarised as evidence for the following.

	Action	Category
	Backfill canals or trenches: brackish/salt marshes Action Link

Backfill canals or trenches: brackish/salt marshes

A paired, site comparison study in 1984 of a backfilled canal crossing predominantly brackish and saline marshes in Louisiana, USA (Abernethy & Gosselink 1988) reported that it developed coverage of emergent vegetation over four years, but that this remained lower than in natural marshes. Statistical significance was not assessed. In 65 of 83 sampled sections, emergent vegetation coverage was lower within the backfilled canal than in adjacent undisturbed marsh (data not clearly reported). Vegetation coverage in the backfilled canal varied with canal width, excavation method, substrate and coverage in the adjacent marsh (factors which were themselves correlated). The backfilled canal contained 2–10 submerged plant species, depending on salinity, with submerged vegetation present at 10–59% of sampling points (data not reported for undisturbed marsh). Methods: In 1979–1980, a canal dug for an oil pipeline was immediately but incompletely backfilled with spoil. The canal predominantly crossed brackish and saline marshes (94% of study area); data for freshwater marshes were combined with weakly brackish marshes. In August 1984, vegetation was surveyed in 83 sections of the canal (each 0.62 km long) and natural marsh adjacent to each section. Emergent vegetation coverage was estimated from aerial photographs. Submerged vegetation was sampled with a rake at 20 points/section.

(Summarised by: Nigel Taylor)