Marine vegetation: a buffer against bad weather

The natural vegetation along the banks of the St. Lawrence River and its marine estuary acts as a barrier against waves and erosion. While standards and regulations increasingly require the implementation of natural infrastructure and shoreline restoration projects to counter the impacts of climate change, engineers have access to little data and few standards adapted to the situation in Québec.

Thanks to the wave canal at the Institut national de la recherche scientifique, Jacob Stolle, a professor of coastal and river hydrodynamics at the Centre Eau Terre Environnement, was able to study how marine vegetation absorbs and diffuses wave energy. This unique facility made it possible for him to replicate the estuary and Gulf of St. Lawrence.

After planting native saltmarsh vegetation in the canal, the researcher and his students, Ganga Caldera and Acacia Markov, spent two years analyzing the influence of seasons and storms on the plants. They began by carrying out functional testing, as this was the first time live plants had been used in the wave canal. The researchers then measured the effectiveness of the plants in preventing storm-induced erosion. Finally, other tests compared the variability of this effectiveness across different seasons.

The data collected was then used to design new models. This research highlights the importance of the long-term presence of vegetation, which helps to mitigate the energy of storms by accumulating sediment.

These results have already been included in the building code guides developed by the National Research Council of Canada and the CSA Group (Canadian Standards Association). As a result, tomorrow's engineers will be better able to optimize the protection of our shorelines against the devastating effects of climate change.

References

• Markov, A., Stolle, J., Henteleff, R., Nistor, I., Pham Van Bang, D., Murphy, E., et Cornett, A. (2023). Deformation of Spartina patens and Spartina alterniflora stems under irregular wave action. Coastal Engineering Journal, 65(2), 325-346. https://doi.org/10.1080/21664250.2023.2195030
• Caldera, G., Stolle, J., Pham Van Bang, D., Murphy, E., et Knox, P. (2025). Seasonal and inter-annual changes in wave attenuation by a constructed salt marsh on a sloping bed, Ecological Engineering, 221, 107758. https://doi.org/10.1016/j.ecoleng.2025.107758