Using wetland vegetation to support coastal resilience

- Ottawa, Ontario

Underwater view of Spartina alterniflora being swayed by the waves. The water is illuminated by a green halo of light on the surface.
Click on the image to view the video.

Marshes, swamps, bogs and other temporarily or permanently flooded areas are all considered "wetlands". They are extremely biodiverse and an excellent indicator of environmental health. Moreover, wetlands absorb and slow down the flow of water while trapping sediment, helping to reduce flood and erosion risks to communities and infrastructure. In the right setting, coastal wetlands have the potential to grow and keep pace with sea‑level rise, becoming self‑maintaining over time. With increasing coastal flood and erosion risks due to climate change and other factors, researchers, engineers and practitioners are looking to better understand how wetlands can be preserved, restored or created as part of nature‑based solutions to manage these risks, while providing a range of other ecosystem services.

The ability of coastal wetland vegetation to reduce the impacts of waves and storm surges has been well documented. However, the majority of previous studies of coastal wetland vegetation has focused on mature marshes, which are not representative of the early stages of a marsh restoration or construction. Recent research at the NRC has investigated how young Spartina alterniflora vegetation, installed in a laboratory flume to represent newly constructed or establishing marshes, responds to waves and currents. Spartina alterniflora, also known as smooth cordgrass, is a salt marsh plant native to Atlantic Canada coastal wetlands.

This research is part of a broader initiative whereby researchers from our Ocean, Coastal, and River Engineering (OCRE) Research Centre are collaborating with partners, including Natural Resources Canada, St. Mary's University, Defence Research and Development Canada, Institut national de la recherche scientifique, Queen's University and the University of Ottawa. Together, they are conducting field monitoring, numerical modelling and laboratory experiments to support the development of design guidance for nature‐based solutions to manage coastal hazard risk in Canada. They even brought wetland plants into our large wave flume and exposed them to various waves, currents and water levels.

So far, the results of the experimental testing with immature Spartina alterniflora indicate that young coastal marshes offer some protection against waves but not to the same extent as established, mature wetlands. This has important implications for adaptive management and maintenance of wetlands in the first few years after restoration or construction.

"It's exciting that the NRC's expertise and specialized physical modelling facilities can play such an important role in enabling improved design of nature‑based solutions to enhance coastal resilience and environmental health in Canada," says Paul Knox, Team Lead, OCRE.

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