Heavy rains, widespread flooding, and devastating landslides have scarred parts of southern British Columbia in recent months. Under climate change, these extreme weather patterns are expected to increase in frequency and intensity, putting pressure on municipalities to manage the resulting excess volumes of stormwater and their impacts.

"Given what we know about climate change," says Chad Hughes, Executive Director of the Elk River Alliance (ERA), the extreme weather systems we saw in late-2021 "could be the new normal year after year, which would be very difficult to manage."

The Elk River Alliance uses science, education, and community collaboration to work towards the sustainable stewardship of the Elk River watershed in southeastern BC. The not-for-profit organization's projects are diverse, but its Elk Valley Stormwater Solutions and Water Awareness project is particularly relevant given BC's November floods.

Elk River Alliance volunteers installed three floating wetlands at Maiden Lake, Fernie, BC, in summer of 2021.

Photo Credit: Elk River Alliance

As part of the project, in 2021, ERA installed three floating wetland structures on Maiden Lake in Fernie to enhance the purification of stormwater entering the lake. They also plan to add up to six similar structures in 2022, with installation, maintenance, and follow-up monitoring that help ERA keep two young people employed.

The undertaking, funded largely by the Healthy Watersheds Initiative, is designed to help mitigate climate change impacts on local communities and the watershed's ecosystems by implementing solutions to manage stormwater effects on the lake.

The Trouble with Stormwater

For municipalities, a major problem with heavy precipitation and flooding is runoff. These rainstorm-caused sweeps of water wash across the ground, over roads, rooftops, parking lots, lawns, fields, and so on, collecting sediment, garbage, oil, tar, fertilizers, manure, and other pollutants. When the water flows into local creeks, rivers, and lakes, it carries those pollutants deep into those ecosystems, harming local wildlife and decreasing the overall health and quality of the watershed.

Many cities use stormwater ponds or wetlands to collect and manage runoff. These features slow and filter the water, allowing many pollutants and sediments to settle before the resulting cleaner water returns to the watershed.

The Elk Valley Stormwater Solutions and Water Awareness project builds on those processes.

Floating Wetland Islands, a Water Remediation Solution

Floating wetlands are rafting water gardens. They can occur naturally or be purpose-engineered — as the Maiden Lake installations were.

If they reach a sufficient size, these free-floating structures reduce waves — encouraging sediment to settle out — shade and cool the water, and provide habitat for fish and other animals. The use of wetland plants such as cattails and sedges is key. Their dense, complex root systems extend deep into the water column, trapping sediment, filtering harmful substances from the water, and even degrading some pollutants. Importantly, by using up excess nutrients, wetlands reduce the chances of eutrophication, which often occurs in places with high fertilizer use.

Intentional wetland installation isn’t a new water treatment technology. In Alberta, for example, a mining company uses similar infrastructure to help purify water from tailings ponds. The structures help clean up algal blooms and oil spills in Manitoba, and Sechelt, BC, uses a related application to treat municipal wastewater.

Floating wetlands are low-cost, low-maintenance structures to help manage and clean municipal stormwater.

Photo Credit: Elk River Alliance

Low Cost; Low Maintenance

The systems are gaining attention due to their low initial investment — the three installed at Maiden Lake cost about $7000 — and minimal upkeep.

"Because this is a natural process, it shouldn't need as much maintenance as an actual water treatment facility," Hughes says. The Maiden Lake installations use native plants adapted to the region; therefore, maintenance simply consists of supplemental planting, thinning, and weeding to retain vegetation quality and species mix.

And the wetlands are anticipated to last at least 10 years. This makes them a viable stormwater solution, particularly for smaller cities and towns.

"The cost of these wetlands over 10 to 15 years comes out to only a few hundred dollars per year," Hughes says. "So, on average, they are very cost-effective compared to any other water remediation methods."

Another benefit is that the wetlands are designed to float. They can adjust to changing water levels brought on by the extreme rainstorms, and other unstable weather predicted to occur more often under climate change.

To help ensure the floating wetlands at Maiden Lake are working as promised and positively impacting water quality, ERA will collect and test water samples from the lake over the coming years. The Elk River Alliance hopes its experience with floating wetlands will encourage other municipalities in southeastern BC to adopt the technology to help mitigate climate change and improve stormwater management in their own watershed communities.

The Elk River Alliance plans to install up to six more floating wetlands at Maiden Lake in 2022.

Photo Credit: Elk River Alliance

To learn more about other HWI-funded projects to help communities prepare for climate change, check out our Projects page.