Discovery Ridge, Calgary NE
2014 - 2015
Discovery Ridge banks stabilization and fish habitat restoration completed for The City of Calgary was an example of the breath of technical expertise available at Westhoff Engineering Resources. The project area is situated inside an area considered by The City of Calgary to be a conservation zone. This meant that typical "hard engineering" bank stabilization techniques were not suitable. Instead Westhoff were tasked with the design of natural bioengineering techniques incorporating elements of natural systems both organic and non-organic. The goal of the project was to increase bank and soil stability and increase the aesthetic and habitat value.
Westhoff completed a hydro-technical analysis for bank stabilization and erosion prevention on the Elbow River near the community of Discovery Ridge. The analysis provided recommendations for the bank stabilization using bioengineering techniques. The design of the bank stabilization involves the combination of a live crib wall and submerged boulders and riprap that extends approximately 100 m.
BIOPHYSICAL/ENVIRONMENTAL TECHNICAL REVIEW
The Biophysical team first carried out an in-depth environmental technical desktop review. This included a review of the all environmental reporting and regulatory approvals on the project site. A full biophysical inventory was completed to baseline the project and to facilitate combining environmental expertise with cutting edge technology and tried and tested techniques in riverbank stabilization works.
The biophysical team prepared the specifications for the willow cuttings to be planted in the live crib wall, designed the restoration plan, supervised on site restoration activities and recommended field fit changes as and when required.
The live crib wall was designed as a structure constructed of untreated cedar logs, live willow cuttings, a biodegradable coconut fiber erosion control blanket and imported topsoil. Five layers of cedar logs; willow cuttings and soil were placed to fill in the space between layers. The crib wall was designed to minimize disturbance near the vertical slope of the wall.
The crib wall enhanced fish habitat by placing riprap at the bottom of the wall, creating shallow pools for spawning habitat and additional bank stabilization. The banks were further stabilized with the planting of live willow cuttings. Rock clusters at the base of the crib wall slowed the velocity of the main flow providing velocity shelters and instream cover. Further enhancements through the planting and establishment of the willows provided cover and food sources.
Further fish habitat enhancements were created by excavating two shallow pools to provide additional instream cover and overwintering habitat. Woody debris from large diameter conifer tree trunks, including branches and root mass, were integrated into rock clusters.