Project timeline: 2022 to 2025
Partners: Flood Debris Management Secretariat (FDMS), Municipality of North Cowichan, Cowichan Valley Regional District (CVRD), Halalt First Nation, Penelakut First Nation, B.C. Ministry of Emergency Management and Climate Readiness, Ministry of Environment and Climate Change Strategy, Ministry of Forests, Indigenous Services Canada
In November 2021, an atmospheric river event caused extensive flooding in many parts of B.C., including along the Lower Chemainus River. That event damaged homes, farms, and businesses in and resulted in closed roads, including the Trans Canada Highway. Another flood on December 26, 2022, forced evacuations and severely impacted homes in the area.
Studies performed for the Province, CVRD, North Cowichan, and Halalt First Nation all conclude the need for better management of the Chemainus River watershed and works in the river to reduce damage caused by flooding. There is general community consensus that gravel and sediment accumulation, scoured banks, and increased debris have increased in recent years, and that works to improve water flow are recommended.
Beginning in 2022, the Flood Debris Management Secretariat (FDMS) has worked with North Cowichan, Halalt First Nation, and some community members on projects to provide some flood protection, sediment removal, and stream channel work.
Works completed, underway, or planned
Left bank side channel (2022)
- This work was completed in November of 2022 and consisted of excavating gravels from an old channel immediately downstream of the highway bridges and flowing past two of the wells drilled for water to supply Chemainus. The intent was to provide a second path for the river to flow once it began high flow rates due to storm events.
Sediment removal (2023)
- An area of the river downstream of the railway bridge and within sight upstream of the Chemainus Road bridge has historically been subjected to gravel deposition and removal. Removal for the first time since 2007 began in September of 2023 with permission from the affected landowners. In all, about 9,000 cubic metres of gravel was removed. This gravel was used, in part, to create a flood barrier wall to better protect Halalt First Nation lands.
Flood barrier wall (2023)
- Computer modelling of a flood barrier wall extending downstream of the highway near the bridges through private property (Russell Farms) and Halalt First Nation showed that it could protect and reduce flooding within Halalt First Nation without harming other properties. The FDMS then funded the project in 2023 using a temporary dike design consisting of geotextile fabric-lined gabion baskets (steel mesh) linked together and filled with gravel excavated from the sediment removal project further downstream. A landowner agreement was signed with the province to provide the rights for the work to be started and completed before high risk of flooding.
- The wall was designed and constructed to be temporary and provide some protection while Halalt First Nation raised and constructed/reconstructed homes. The fabric is expected to last 5 years in these exposure conditions and will result in a semi-permeable barrier. The landowner agreement terminates 3 years after commencement, and at that time, the province will cease to maintain, and it may remove the barrier.
- Flood waters did not impact the barrier in the winter of 2023/2024 and remains untested.
Bendway weirs (late 2024)
- Bendway weirs are low-level, totally submerged rock structures positioned from the outside bank of a riverbend, angled upstream toward the flow and are used to reduce bank erosion by redirecting the main flow of the river away from the riverbank. The FDMS approved the concept and funding in 2023, and construction began in August 2024. A total of six weirs will be installed on the river's right bank downstream of the highway bridges to reduce erosion along this bend. Other related works will be completed between the weirs and the flood barrier to help control flood waters. The bendway weirs do not impact flooding but are expected to reduce erosion and, thus, sediment downstream.
Transect survey (2024)
- Ten sites are being surveyed for comparison to previous surveys. This will provide information regarding changes in the river and determine if any changes are directly or indirectly attributed to the recent works.
Left bank side channel (possible 2025)
- Depending on information gathered during the transect survey, additional work in the left bank side channel will take place. This work could include gravel removal in the summer of 2025.
Chemainus Road flood gates (2024)
- Ministry of Transportation and Infrastructure (MOTI) plans to install vehicle gates across Chemainus Road near the intersection of Chemainus/Westholme/Mount Sicker Roads and on Crofton Road near the intersection of Chemainus Road. These gates would close the road to traffic during times of flooding.
- MOTI will be meeting with First Nations and municipal staff to discuss operation and a protocol for the use of the gates.