Flood Control In Action

Flood Control
In Action

Learn about options for flood control infrastructure in the lower Fraser

To explain how flood control structures can help or hurt salmon habitat, we’ve created a series of animations showing how different types of floodgates and pump stations work.

To explain how flood control structures can help or hurt salmon habitat, we’ve created a series of animations showing how different types of floodgates and pump stations work.

Floodgates

Floodgates prevent high waters in a river, due to spring snowmelt (freshet), or incoming tides, from backing up into tributaries and potentially flooding land behind dikes.There are three common types of floodgates in this region.

The most fish-unfriendly design: Top-mounted floodgate

Floodgates prevent high waters in a river, due to spring snowmelt (freshet), or incoming tides, from backing up into tributaries and potentially flooding land behind dikes.There are three common types of floodgates in this region.

The most fish-unfriendly design: Top-mounted floodgate

Floodgates prevent high waters in a river, due to spring snowmelt (freshet), or incoming tides, from backing up into tributaries and potentially flooding land behind dikes.There are three common types of floodgates in this region.

A more fish-friendly design: Side-mounted floodgate

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.

A more fish-friendly design: Side-mounted floodgate

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.

A fish-friendly solution: Vertical sluice gates

Sluice gates, if implemented properly, can be 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.

A fish-friendly solution: Vertical sluice gates

Sluice gates, if implemented properly, can be 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.

A fish-friendly solution: Self-regulating gates

Self-regulating gates are a modified version of a top-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.

A fish-friendly solution:
Self-regulating gates

Self-regulating gates are a modified version of a top-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.

Pump Stations

Pump stations are installed on waterways where there is a need to move high volumes of water out of creeks to prevent flooding behind the dikes. Where floodgates are passive and open depending on water levels both on the creek side and river side, pump stations will turn on when water levels in the creek reach a predetermined level, and pull water into the mainstem river. Juvenile salmon, other fish and amphibians inhabiting these creeks are drawn to flowing water. As such, when pumps turn on and start pulling water, they also pull other animals into the pumps. The lower mainland has about 100 pumps of which only a handful are fish-friendly. Most pump stations are not designed with fish in mind as such there is a high rate of fish and amphibian mortality linked to these structures.

Not fish-friendly: Impeller pump

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 mainstream river get too high. Once the gate closes, water and fish are forced through the pumps. Though fish-unfriendly designs are much more common, there are fish-friendly 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.

Not fish-friendly:
Impeller pump

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 mainstream river get too high. Once the gate closes, water and fish are forced through the pumps. Though fish-unfriendly designs are much more common, there are fish-friendly 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-friendly: Axial pump

The fish-friendly axial pump works features two fixed curved blades with larger spaces in between. These larger spaces and curved blades allow fish to enter 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 stati

Fish-friendly: Axial pump

The fish-friendly axial pump works features two fixed curved blades with larger spaces in between. These larger spaces and curved blades allow fish to enter 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 stati

Fish-friendly: Archimedes screw pump

This animation shows the Archimedes screw pump. These pumps, which look like giant screws, rotate in place and act almost like a conveyor belt for water (and fish). They often turn at a lower speed compared to the impeller pump, 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 pump and the walls inside the pump chamber. An Archimedes screw pump often requires a complete rebuild of a pump house which significantly increases the cost to upgrade the infrastructure to make it fish-friendly.

Fish-friendly: Archimedes screw pump

This animation shows the Archimedes screw pump. These pumps, which look like giant screws, rotate in place and act almost like a conveyor belt for water (and fish). They often turn at a lower speed compared to the impeller pump, 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 pump and the walls inside the pump chamber. An Archimedes screw pump often requires a complete rebuild of a pump house which significantly increases the cost to upgrade the infrastructure to make it fish-friendly.

Dikes

A dike is a long wall, berm or embankment built along rivers, drainage ditches or the ocean to prevent flooding from high water levels. In the lower mainland there are over 600km of dikes that protect over 350,000 people, communities, important infrastructure like roads, transmission lines and farm lands. Over 80 per cent of dikes in the lower mainland are at risk of overtopping or being breached by flood waters. As the need to upgrade dikes increases, we want to suggest two natural flood defense solutions. These two examples combine grey solutions (dikes) with natural, regenerative solutions.

Fish-friendly: Setback dikes

Fish-friendly: Setback dikes

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.

Fish-friendly: Dike breach

Fish-friendly: Dike breach

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.

To learn more about our Connected Waters campaign and to send a letter asking decision makers to change the way we manage for floods, visit Connected Waters

This work was possible thanks to our volunteer animation creators, Nathan Ross and Paul Pajot!

Nathan Ross is a Masters student at UBC School of Architecture and Landscape Architecture. 

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. 

We would also like to thank UBC’s Coastal Adaptation Lab for their support with this project.