During the 2010s, the City of Kelowna experienced multiple floods in the Mill Creek area due to high water levels during spring freshets. Climate change increased the 200-year flows from 12 m³/s to 24.3 m³/s, overwhelming existing flood control structures. A diversion structure constructed back in the 1980s divert excess water toward Mission Creek to reduce the flood risk in downstream reaches of Mill Creek. The project aimed to improve the city’s flooding issues, enhancing public and crew safety and reducing the risk of property damages. The objectives included improving the hydraulics of the diversion structure, increasing the amount of water diverted towards Mission Creek, managing debris, and improving the upstream pass for spawning fish that had been previously blocked by the original structure. At the time, this was the city’s largest and most complex project, primarily due to the diversion structure and its complicated geometry to hydraulically model, study and analyze, as well as its impact on managing water behaviour during floods.

The project incorporated innovative solutions such as an inclined trash rack, a fully automated trash rake, an access ramp for debris removal, and automated gates based on water levels. Sustainable engineering guided the design of fish-friendly infrastructure such as fish pools, floodplains, and large-woody-debris, and engineered creek riffles, promoting ecological health while mitigating flood risks. Our sustainable approach significantly minimized tree removal, reducing the number of cuts by more than half. A restoration plan was implemented, ensuring that three trees were planted for every tree removed. By integrating sustainable practices with cutting-edge engineering, this project not only addressed immediate flooding concerns but also established a forward-looking framework for resilience in the face of climate change.

Our team tackled a long-standing flooding issue with a sustainable, safety-focused approach to enhance flood protection. The initiative upgraded the Mill Creek diversion structure, which diverts water to Mission Creek to reduce downstream flood risk, enhancing flood management, hydraulic capacity, and fish passage. Environmental restoration created biodiversity along Mill Creek.

Hydraulic modelling in 2020 revealed a 200-year peak flood flow increase from 12 m³/s to 24.3 m³/s, making the existing structure inadequate. As such, Kelowna retained MidSea Engineering (now part of CIMA+) to upgrade the infrastructure as part of the $55M Mill Creek Flood Protection initiative. A decision matrix was developed to select the most optimum solution based on cost, safety, and improvements. The project was executed in two phases: Phase 1 involved designing and constructing a dam under BC Dam Safety Regulation, and Phase 2 included dike design and construction along creek banks under Dike Maintenance Act. This project created a controlled flood containment system, improving flood mitigation. This approach allowed Phase 1 construction to proceed while awaiting Phase 2 permits, expediting the timeline to enhance safety and client service. Permitting included Water Licence, Dike Maintenance Act, Dam Safety Regulation, and Fisheries Act approvals.

The project enhanced safety, hydraulic efficiency, and climate resilience while integrating debris management and environmental stewardship.

The project successfully enhanced flood resilience by upgrading the diversion structure, increasing water diversion, and improving fish passage. Innovative solutions, including an automated trash rake and fish-friendly infrastructure, mitigated flood risks and supported ecological health. Sustainable practices reduced tree removal and implemented a restoration plan. This project significantly improved safety, hydraulic efficiency, and climate resilience, benefiting the community long-term.