Assessment of Spawning Platforms Constructed to Remediate Flood Damage to Kokanee Habitat: The Case Study of the Lower Powers Creek Flood Recovery Project, West Kelowna, British Columbia
Leif Burge, PhD
Stantec Consulting, Inc.
Kelowna, British Columbia
Authors: Joe Kennedy and Leif Burge, Stantec Consulting, Inc.
Powers Creek, located in West Kelowna, within the Okanagan valley of British Columbia, Canada, experienced high flows and sediment deposition in the spring of 2017, resulting in damage to public infrastructure and degradation of kokanee salmon (Oncorhynchus nerka) spawning habitat. Non-anadromous, land locked, kokanee are in decline in the Okanagan and the restoration of degraded spawning areas in Powers Creek was identified by regulators as a key requirement for the flood recovery. Natural channel design techniques were used to increase the conveyance capacity of the channel to decrease the flood risk, while providing critical spawning habitat for kokanee. Spawning platforms were designed and constructed for the project. The platforms were assessed to determine whether particle size, depth, velocity and Froude numbers were suitable for spawning kokanee. The Froude number results are the first documented for spawning kokanee. Seven out of nine platforms were stable, and generally provided gravel substrate suitable for spawning kokanee (between 25 mm and 50 mm). The platforms generally provided spawning habitat for kokanee within the preferred values for depth, velocity, and Froude numbers. Spawning counts indicate that eight out of nine platforms had spawning activity. Some areas that provided suitable substrate, depth, and velocity were not used by spawning kokanee. This is likely due to kokanee populations that are too low to utilize the full suitable spawning area. Further monitoring of the platforms is recommended to determine use of the platforms over time. Additional research, including the collection of depth and velocity data to refine Froude numbers at redds and detailed enumerations would provide valuable data on the preferred spawning habitat for kokanee in Powers Creek.
About Leif Burge
Dr. Burge is a nationally recognized river scientist at Stantec with over 20 years of experience solving applied river problems and conducting research. Leif’s wide-ranging experience includes hydrotechnical assessment of bridges, hydrotechnical geohazard assessment, natural channel design, hydraulic modelling, channel assessment, sediment management, sediment transport, river stability, environmental impact assessment, assessment of dam breaches, flood response and recovery, and fluvial habitat projects.