water resources
Demonstrating the Benefits of
BIOENGINEERING Calgary’s ‘living laboratory’ openly shares new findings. By Mike Gallant, P.Eng.
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www.canadianconsultingengineer.com
both common and new techniques and openly shared its documentation, research findings and performance monitoring results through a municipal website, www.calgary.ca/BDEP, which was launched in 2020. Novel techniques Bioengineering is still an emerging field in Canada. In Alberta, specifically, with a low rate of vegetation survival (typically only around 50%), projects have not always been successful. The BDEP, however, demonstrated how higher vegetation survival rates could be achieved using best practices. Indeed, through focused attention to vegetation design, installation and maintenance, performance monitoring shows the BDEP’s rate of vegetation survival is 80%. This was accomplished by implementing 14 different techniques at 10 treatment areas with a variety of hydraulic, geotechnical and environmental conditions. Of these techniques, half were novel to Calgary, including: • three new techniques for vegetating existing riprap bank protection works to enhance aquatic habitat, wildlife passage, riparian health and esthetics. • a new vegetation preparation techMarch/April 2021
nique to allow for summer construction, when live cuttings should not be used, to provide construction schedule flexibility. • a new scour protection technique equivalent to riprap that uses only vegetation and locally available materials. • a new technique that combines live cuttings with rooted plants to increase biodiversity, wildlife habitat and nitrogen fixing. • a new technique that incorporates submerged refuge shelters under a timber crib wall to provide fish habitat along the bank. Challenges and resolutions During the 2013 flood, the Bow River’s velocity reached 4 to 5 m/s and the riverbed dropped by about 4.5 m at the site, forming the river’s deepest scour hole in Calgary. After conducting a detailed analysis, KWL designed a self-launching riprap scour apron that included rock structures for fish habitat. When the BDEP’s design was nearly complete, a new transit bridge within the site was announced. KWL collaborated with the bridge design team to minimize the need to redesign the BDEP. They worked to increase the bridge’s dimensions to accommodate
Photo courtesy KWL.
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or Alberta, the Bioengineering Demonstration and Education Project (BDEP) is a significant initiative that showcases next-generation techniques for protecting riverbanks from flooding, as an alternative to such conventional methods as rock riprap. About 100 trees, 2,300 shrubs and 30,000 live cuttings were planted to improve riparian (i.e. aquatic-terrestrial) health. Alberta Environment and Parks partnered with the City of Calgary to undertake the BDEP to mitigate impact to fish habitats and improve riparian health along a 680-m stretch of the Bow River in the community of Inglewood, in the wake of a 2013 flood recovery program. As design lead and engineer of record, Kerr Wood Leidal Associates (KWL) of Calgary completed the project’s design in collaboration with Hemmera Envirochem (prime consultant), Terra Erosion Control (bioengineering specialist), Polster Environmental Services (bioengineering specialist), O2 Planning & Design (landscape architect), and Thurber Engineering (geotechnical engineer) between July 2016 and September 2017, followed by construction by DFH Enterprises from February 2018 to June 2019. The project successfully showcased
