Suchergebnisse

AbstractChannel form and biotic features create a network of niches that facilitate sediment deposition, creating habitat for lamprey larvae or ammocoetes. Flood conveyance management and channel maintenance can lead to a general loss of instream features that permit biotic diversity and sediment deposition. Studies presented here identified the potential for loss of both ammocoete habitat and populations during channel maintenance, in the absence of mitigation measures. Recovery of population structure and density of ammocoetes commenced within 12 months and took 3 years to reach preimpact levels in one study. In another, where mitigations were implemented, no impact was evident 12 months after channel maintenance. In view of the conflict between conveyance for flood management and conservation of designated Habitats Directive species (lamprey), there is a clear need for practical ammocoete mitigation measures to be developed and implemented in river engineering works.

AbstractScientific studies (1990–2000) on the impacts of channel maintenance on the river corridor biota and habitat of Irish arterially drained channels identified strategies that would reduce adverse impact or provide benefit. A 10‐point training programme was developed from these strategies and was rolled out to all Office of Public Work (OPW) field staff, engaged in channel maintenance, during 2003. Follow‐up site visits indicated a strong degree of implementation in respect of particular actions. It was also apparent that there was a low level of uptake of value‐added options, particularly those where strong liaison with fisheries was feasible. It was evident that some of the 'enhanced maintenance' diggings in the cross‐section would enhance hydromorphology elements in the channel, consistent with Water Framework Directive requirements. All 10 elements are now being pursued in a new 5‐year programme (2008–2012).