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THE PROBLEM
Much of the flood control infrastructure in the Lower Mainland is aging and outdated, leaving communities at risk of flooding. It also often blocks fish from moving between rivers and oceans to streams and wetlands they seek for food, refuge, and rest. In the lower mainland its estimated that over 1500 km of salmon habitat is blocked by 156 pieces of flood control infrastructure.
However, there are increasingly more examples of flood control infrastructure that are friendlier to fish than others. Check out our explainer animation videos created in collaboration with Watershed Watch Salmon Society below to learn more about the good, the bad, and the ugly of flood control infrastructure.
Flood Infrastructure Animations
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These animations describe how flood infrastructure either disconnect or in some cases help to connect fish from rivers and ocean to the streams kept behind them.
Flood Infrastructure Animations
TOP MOUNTED GATE
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Top-mounted floodgates are the least fish-friendly gate design and some of the most commonly used. These gates are often heavy, with cast iron flaps that only open once the water level inside the gate is much higher than the water level outside the gate. Because the resting position of the gate is closed, and such a large difference in water height is required, these gates rarely open and are often only open for short periods of time. When they do open, the water rushing out can be flowing too fast for fish to swim into the gate. The opening can also be too narrow for larger fish to pass through.SIDE MOUNTED GATE
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Side-mounted gates are a somewhat more fish-friendly design. Unlike top-mounted gates, these gates are oriented like a door. However, like top-mounted gates, side-mounted gates require a higher water level inside the gate than outside the gate to open. They also have a closed resting position. The key difference between these gate types is that side-mounted gates require significantly less water level difference to open. These gates are also made of much lighter materials such as aluminium, this means these gates swing open wider, for longer, and more often than top-mounted gates. These gates do not create flows as fast as top-mounted gates do either, making it easier for fish to pass through once the gate opens. The gates close when water levels in the river rise, protecting the communities and land behind the dike.VERTICAL SLUICE GATE
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Sluice gates, when implemented and managed properly, are a fish-friendly solution to flood control. These gates may be operated remotely or manually and may either default to an open or closed position depending on the intended use. If defaulting to an open position, as in this animation, the sluice gate offers unobstructed passage to fish for the majority of the season. Fish only become isolated when water exceeds a predetermined level and the gate closes. If defaulting to a closed position, this gate is not fish-friendly and creates a significant barrier to fish passage. These are best used where there is no influence of tidal cycles, especially if manually operated.SELF-REGULATED GATE
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Self-regulating gates are a modified version of a top or side mounted gate. They have a counter-balance mechanism, such as a float and a more buoyant gate flap that results in the gate being open more often, and for longer periods of time. The only time the gate closes is when the water levels on the river gets high enough to push the float up, which closes the gate. This means the default position of the gate is open, making it the most friendly gate design for salmon. Designs vary widely, using remote sensors, floats, or cables sensitive to resistance to activate gate closure and opening. Examples include Nehalem Marine, Golden Harvest, and Juel Tide gates.IMPELLER PUMP STATION
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An impeller pump is essentially a fan blade that forces water through a pipe from the creek side out into the mainstem river. As one might imagine, this is not fish-friendly at all! Fish mortality with these types of pumps can be quite high, as fish get chopped up and killed, or injured severely, making them prone to predation and disease. There can also be drastic pressure changes inside the pump that can pop the swim bladders of fish. Not shown in this animation but typical to most stations, the pump is paired with a floodgate, but the gate closes when the water levels in the river or ocean get too high. Once the gate closes, there is only one way water and fish can get out from the stream and that is through the pumps. Though fish-unfriendly designs are much more common, there are fish-friendlier versions of impeller pumps that have larger spaces between the blades, rotate at slower speeds, and are housed in cages to prevent fish getting caught between the blades and the sides of the pump station.FISH-FREINDLY AXIAL PUMP STATION
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The fish-friendly axial pump features two fixed curved blades with larger spaces than a typical impeller pump. These larger spaces and curved blades allow fish to enter and travel through the pump with greater ease. The blades are paired with innovative guide vanes to minimize fish disorientation and limit extreme pressure differences. These are easy to install and can offer a simple retrofit to an existing pump station.ARCHIMEDES PUMP
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These pumps, which look like giant screws, rotate in place and act almost like an escalator for water (and fish). They turn at a much lower speed compared to impeller pumps, making them less turbulent to fish, reducing risk of mortality or injury. The screw is positioned tightly in the pump station structure to prevent fish getting caught between the threads of the screw and the walls inside the pump chamber. An Archimedes screw pump often requires a complete rebuild and expansion of the footprint of a pump house which significantly increases the cost to upgrade the infrastructure to make it fish-friendly.DIKE BREACH
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This animation depicts the intentional opening up of a dike at certain strategic locations to allow the flooding of land behind the dike. This technique is used to reconnect floodplain habitats, where safe to do so, restoring fish access to side channel and wetland habitats and providing flood storage in areas that would otherwise experience frequent threat of flooding. A good example of where this would work is the Pitt-Addington marsh in upper Pitt Meadows where strategic openings in the dikes can reconnect the floodplain, provide extra fish habitat and additional flood storage.SETBACK DIKE
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A setback dike is built away from the riparian edge of a river, allowing the river room to flood. This creates naturalized channels in the floodplain that increases the storage capacity of the waterway to hold more water and improves side channel habitat for salmon and other fish, protecting them from being washed downstream with flood waters. Where appropriate, setback dikes can protect the built environment by setting roads and building back from the river’s floodplain. The land in front of the dikes can be used as wetland habitat and walking trails outside of high water events.This work was created in collaboration between Watershed Watch Salmon Society and Resilient Waters. It was begun by volunteer animation creators, Nathan Ross and Paul Pajot and finished by Kerel Alaas, as well as many advisors who provided feedback during its development.
Nathan Ross is a landscape architect who was studying at UBC School of Architecture and Landscape Architecture's Coastal Adaptation Lab who helped to kick off the original design.
Paul Pajot (@paul_pajot) is a visual communication designer and founder of @coucou_design, a design studio based in London, England and helps organizations bring ideas to life from space to screens.
Kerel Alaas is a Vancouver based animator and ECUAD graduate who grew up among turkic nomads in Siberia. Alaas' role was funded through the Canada Summer Jobs Program (via Watershed Watch Salmon Society).
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