Abegweit Conservation Society
Three Low Profile Structures for Habitat Rehabilitation in Midgell River
The purpose, or main goal of the project was to initiate the establishment of specific habitat features, deeper areas/pools, while maintaining channel stability, that have been identified as lacking in a selected section upstream of the head of tide in the Midgell River. To attain the goal mild adjustments to the channel maintenance flow pattern were made by installing 3 low profile deflector structures. The change in flow pattern will alter the stream bed conformity by rearranging substrate materials creating deeper area/pools and subsequent riffles.
Other objectives and progressive tasks that needed to be successfully completed during the project were:
Training was provided for the Abegweit Stream crew in the first week of July. To follow social distancing restrictions, the training was held onsite for three days. It included knowledge sharing about channel, bank and riparian zone structure and function, water dynamics and surveying techniques. Cross-section measurements of the channel were carried out as well as a Rapid Geomorphic Assessment. These activities provided critical information used for the selection of the most optimal locations to install the new structures. Plans were drawn up according to data collected at the location.
The next steps were to clear an access trail into the site and the clearing of old structure remnants from the 1980's. The remnants material (mostly rocks) from the old structures was repurposed where possible into the new structures.
Monitoring activities to support the project were completed as part of the "before" and "after" evaluation of the project. The activities included an electrofishing survey, CABIN survey, redd survey and ongoing water temperature monitoring at the site.
The three structures were installed using wood dowel instead of rebar in keeping with the fact that stream channels natural migrate side to side and habitat features such as pools and riffles also naturally move incrementally downstream within the stream corridor.
Other stream habitat maintenance work of increasing and retaining connectivity along the main branch of the Midgell River was also completed.
The initial benefit to salmonids and other aquatic species is the creation of deeper areas within the channel for protective cover from predators as well as holding areas for return spawners. A benefit to the riparian zone is the slowing of bank erosion. Since the banks are lined with mature trees that provide shade and undercut bank cover, decelerating their inevitable collapse will result extending the tree's positive benefits (food source & shelter) to wildlife, aquatic and terrestrial species.