We need flood protection to safeguard our homes and communities from rising water levels, but did you know that some flood protection can be damaging to wild salmon and their habitat?
Floodgates are typically installed where the Fraser River connects to smaller waterways such as side channels, creeks, and sloughs which are susceptible to flooding. These gates are closed when water level in the Fraser is high (think high tides or spring freshet) to prevent water backing up into adjacent waterways and causing flooding.
How do floodgates affect salmon?
Salmon use these smaller waterways through all their life stages: they are used as spawning grounds by adult salmon, rearing grounds by salmon fry such as Interior Fraser Chinook and some salmon, coho in particular, overwinter in these waterways before heading out the next year with the spring freshet. This means salmon need access to these waterways for many months of the year.
But, what is a salmon to do when the gates are closed? They instinctively know where they are headed, so if their passage is blocked, they need to find another waterway to call home. This act in turn reduces the amount of salmon nutrients left in a waterway bringing with it cascading effects on the local watershed.
How do floodgates affect waterways?
Floodgates that block fish access, also block water flows, creating stagnant waters. Imagine a creek gently flowing out to meet the Fraser River — wild salmon resting in the shade, a great blue heron stalking its prey. Now imagine what happens when you put a gate at the end of this waterway. The flow of water stops and species that prefer stagnant waters move in.
Across the lower Fraser, waterways have become choked with a variety of invasive species, such as the notorious aquarium plant parrot feather. These non-native plants quickly overtake waterways, outcompete native plants, and remove dissolved oxygen from the water as they decay, making the once thriving ecosystems uninhabitable for wild salmon.
What’s the solution?
One solution is to update floodgates to models that have been designed to be fish-friendly. These flood gates stay open most of the time, when flooding is not a risk, allowing the free passage of water and fish.
For communities that lack funding to immediately install new flood infrastructure, an easy solution is to have someone manually open fish gates in times when flood risk is low. While this solution does not require any additional infrastructure costs, it does rely on human time and effort.
Watershed Watch is campaigning to ask the federal and provincial government to ensure that regional flood risk strategies account for wild salmon, to support communities to install fish-friendly infrastructure and to restore the waterways of the lower Fraser Valley so they can once again provide the rich habitat needed to support abundant wild salmon runs.
Please sign and share our Connected Waters petition, calling on our governments to prioritize salmon habitat on the lower Fraser River when aging flood infrastructure is being upgraded.