For decades, when rivers spilled their banks, our instinct has been to fight back by building dikes and concrete walls and channelizing our waterways. But what if we approached flooding differently? What if managing floods could also mean restoring healthier rivers and better habitat for salmon?

If you follow our work here at Watershed Watch, you’ve probably heard us talk about how outdated flood infrastructure across the Lower Mainland of B.C. is killing salmon and cutting them off from the habitats they depend on. You may have explored our Disconnected Waters map, which shows the 1,700 km of impacted habitats, or seen us call for more fish-friendly approaches to flood management.

You might have also come across our discussions about the different ways to manage flood risk. On one end of the spectrum are fully engineered systems designed to control the flow and movement of water. On the other end are tried and tested nature-based approaches that slow, store, and absorb water using wetlands, floodplains, and natural landscapes.

Habitats Program Director Lina Azeez

In this blog, we’ll break it down, explaining what fish-friendly flood infrastructure, green infrastructure, and nature-based solutions are, how they work together to make us safer, and what they look like in practice. We’ll also share real-world examples from the Lower Mainland that show what’s possible when we rethink how we manage for floods.

The Grey-Green Infrastructure Spectrum

What is Fish-friendly Flood Infrastructure?

Across many flood-prone regions, status quo flood infrastructure, such as dikes, floodgates, and pump stations, was built with one goal in mind: moving water away from people and farmland as quickly as possible. While these structures can reduce flood risk, they often come at a cost to fish and aquatic habitats. They can block salmon migration routes, drain critical wetland habitat, or trap fish behind flood control structures.

Top-mounted floodgates are the least fish-friendly floodgate design.

Conventional flood infrastructure can also increase our risk by creating a false sense of security, encouraging more development in naturally flood-prone areas behind dikes and barriers. When those systems are overtopped or fail, the consequences can be catastrophic and severe.

Fish-friendly flood infrastructure is designed to reduce flood risk while also allowing fish to move safely through waterways and access their habitat. The sloughs, side channels and small streams that are being blocked by obsolete structures are vitally important for keeping our wild salmon runs healthy and abundant.

Instead of treating flood protection and ecological health as competing goals, fish-friendly designs recognize that healthy floodplains and rivers are part of resilient flood management.

Example 1: Fish-friendly floodgates

Traditional top and side-mounted gates typically stay closed when river levels rise, preventing fish from entering floodplain channels. Fish-friendly floodgates are designed to open more frequently or allow passage even during changing water levels. This helps juvenile salmon reach side-channel habitats off the mainstem river that are important for feeding, rearing, and refuge. Examples include the sluice-style fish-friendly gates on the Lower Agassiz Slough and Joe’s Lake off Nicomen Slough, and the self-regulating tide gates on a side channel to the Coquitlam River and Spencer Creek in Maple Ridge.

Sluice-style fish-friendly floodgate being installed at Joe’s Lake in Deroche. Credit: Resilient Waters

A self-regulating floodgate can be programmed to stay open to allow for better flow of water and better movement of fish. Photo credit: Golden Harvest/Resilient Waters

Example 2: Fish-friendly Pump Stations

Pump stations move water from behind dikes into nearby rivers. Conventional pumps can injure or kill fish that are drawn into them. We call them “meat grinders”. Fish-friendly pump stations use specially designed pumps and screens, and operate at a lower speed to significantly reduce harm to fish moving through the system. Currently, no pump station is fully fish-friendly, but initial research has shown that fish-friendly pump stations are friendlier and safer than conventional. The Netherlands has some of the best fish-friendly pumps and station designs in the world. The enclosed fish-friendly screw pump is one such pump that has dropped fish mortality and should be imported and adopted in B.C.

There are only a handful of “fish-friendly-ish” pump stations in the Lower Mainland. Some examples include Hammersley Pump Station in Agassiz, the Yorkson Pump Station in the Township of Langley and Mimi Creek in Harrison Hot Springs, all of which are shown to still disorient or kill fish, albeit at a much lower rate than conventional pumps. A new fish-friendly station coming online in the next year is the Maple Creek pump station in Port Coquitlam. It carries an estimated price tag of $12 million, which includes the pumps, the pump station building, generators, electrical kiosks and a flood box.

What is Green Flood Infrastructure?

Green flood control structures work with the water cycle, using natural features or nature-inspired designs to slow, store, and manage floodwaters. By capturing water where it falls and allowing it to soak into the ground (think rain gardens, green roofs and permeable pavements), green flood infrastructure can reduce flooding, improve water quality, cool urban areas, and create habitat for salmon and other wildlife.

Rather than relying solely on hard infrastructure like concrete channels and high dikes, green flood infrastructure absorbs, stores, and slows water across the landscape.

Fish Flow Innovations in the Netherlands has designed a closed Archimedes pump that is nearly 100% fish-friendly.

You often find green flood infrastructure in more urbanized or developed areas where natural landscapes have been replaced with pavements, concrete, and buildings that cause rainwater to quickly flow over the surface to storm drains and not get absorbed into the ground, thereby overwhelming drainage systems.

St. George Rainway, completed in 2025. Photo: City of Vancouver

Example: Bioswales

A bioswale is a living, breathing storm drain! It’s a vegetated channel that absorbs stormwater runoff. As water moves through a bioswale, the plants, soil and substrates capture heavy metals, oils and sediments before the water reaches a stream. The City of Vancouver has over 400 green rainwater systems in the city that collect and clean over 32 hectares of urban land. The St. George Rainway is one such bioswale that runs along four blocks in Vancouver. It can capture and filter 17,000 cubic meters of rainwater per year (about 113,000 bathtubs) that would otherwise overwhelm the city’s sewer system. The bioswale cost $1.6 million to build and has saved the city about $16 million in sewer pipe upgrades in a neighbourhood prone to flooding. Expansions are planned for the area.

What are Nature-based Solutions?

While engineered infrastructure plays an important role in flood management, there is growing recognition that working with nature can often provide more resilient and cost-effective protection.

Nature-based solutions use natural landscapes and processes, such as water flow, sediment transport and habitat formation to reduce flood risk while providing additional benefits like habitat restoration, water quality improvements, and climate resilience. They simultaneously provide measurable benefits for people and the ecosystem.

Rather than trying to completely control rivers, nature-based approaches restore the natural functions of floodplains, wetlands, and forests that help absorb and slow floodwaters.

From the Nature-based Solutions Toolkit by David Rojas, Habitat Analyst, 2025

Example 1: Riparian Buffers and Wetland Restoration

Forested banks and restored wetlands work in tandem: riparian buffers slow and filter water as it moves from the land into a stream, while wetlands act as natural reservoirs that absorb floods and release water slowly during dry periods. Restoring wetlands can reduce flood risk while improving water quality and providing critical habitat for salmon, birds and other animals. In the Lower Mainland, we’ve lost over 85 per cent of the original wetland ecosystems. Many of the communities hardest hit by the 2021 atmospheric river and floods were built in areas where these wetlands and floodplain forests once stood.

Example 2: Floodplain Reconnection

Since the late 1800s, the lower Fraser River and its tributaries have been confined by dikes and development, cutting them off from their natural floodplains. One of the most powerful things we can do is to reconnect rivers to portions of their floodplain, allowing water to spread out during high flows, reducing downstream flood peaks all while creating valuable habitat for fish and wildlife.

Recently, this work has been done in the Pitt River floodplain in an area known as Addington Point. The area was diked for agriculture in 1897 which proved unsuccessful. It was converted to a Wildlife Management Area in 1972. Small breaches were punched into the dike in 2004.

In 2025, to restore wetland function, salmon access and floodplain reconnection, approximately 300 metres of the dike was removed at the north end and two breaches were created along the east flank, and a 300 meter long channel to the Pitt River was re-established.

Coupled with channel widening, this work is expected to allow water into the entire wetland when tides are high or during high flow events, reconnecting a large swath of historical floodplain habitat for salmon. These breaches will be studied to better understand the benefits of reconnecting the marsh back to the Pitt River.

Aerial photo of Addington Point Marsh, 1978

Initial project scope for the Addington Point Marsh. Image credit: Resilient Waters

In Conclusion

Taken together, fish-friendly flood infrastructure, green flood infrastructure and nature-based solutions, point us toward a more balanced and resilient way of living with water. Instead of relying solely on hard, single-purpose structures, this approach blends engineered and natural solutions across the green–grey spectrum, reducing flood risk while restoring the ecological processes that rivers, floodplains, and salmon depend on. The result is not just safer communities, but healthier, more connected watersheds that can better withstand a changing climate.

Feature image credit: Eiko Jones