Sea level rise
Coastal areas, which are already vulnerable to climate hazards, will be increasingly at risk due to global warming. Rising sea levels cause gradual or episodic flooding during storms, as well as coastal erosion. This has impacts on:
coastal communities
the natural environment
the built environment
Impacts on coastal communities
Rising sea levels can directly threaten the health and safety of coastal communities. They intensify coastal flooding, damage infrastructure, overload water systems and promote saltwater intrusion into drinking water sources.
Due to saltwater intrusion, the quality and safety of water supplies for communities that rely on groundwater resources may also decline. This progressive contamination of surface and groundwater can increase the risks of cardiovascular, renal and infectious diseases.
In addition to the risks to physical health and drinking water, more frequent and intense coastal flooding can also affect the safety of nearby communities. It is estimated that safety costs related to coastal flooding events could reach $23 million per year by 2050.
On the social level, rising sea levels can lead to the permanent submergence of certain areas, forcing populations to relocate to less affected regions, which disrupts daily life and community cohesion. It can also contribute to mental health issues such as anxiety, depression and post-traumatic stress disorder.
Impacts on the natural environment
In terms of the natural environment, rising sea levels could lead to the migration of the salt front, meaning that saltwater in the St. Lawrence River could move upstream to where there is currently freshwater. This could have impacts on the supply of drinking water for municipalities with water sources located in this area of the river. Aquatic ecosystems may also suffer consequences.
Although there are still uncertainties regarding the extent of the salt front migration zone in Quebec in a future climate, the fact remains that changes in salinity conditions will occur over time.
Research project | The salinity of the St. Lawrence River under scrutiny: For a better understanding of the anticipated impacts of its variability on the drinking water supply of the CMQ
This project improved the understanding of the current and future spatial and temporal variability of salinity in the saltwater transition zone to support local stakeholders in their decision-making.
Rising sea levels can also exacerbate coastal squeeze and lead to the degradation or even gradual disappearance of coastal ecosystems like beaches and marshes. Coastal squeeze is a phenomenon whereby a coastal ecosystem is trapped between rising water, which causes erosion of the shoreline, and a natural or artificial obstacle, like a wall.
By 2060, it is estimated that 25% of beach and marsh areas could disappear if no measures are taken to limit the impacts of coastal squeeze. These natural environments are important, as they provide natural protection against coastal hazards by mitigating the risks of erosion, submergence and sea level rise.
Impacts on the built environment
By gradually submerging land and increasing erosion, rising sea levels can weaken essential infrastructure like ports, roads, bridges and homes. Storms and high tides exacerbated by rising sea levels can also accelerate the deterioration of dykes or embankments, which can increase the risk of coastal flooding and property losses.
Water management infrastructure is also vulnerable to sea level rise. Saltwater intrusion into drinking water systems and treatment plants can compromise the quality of drinking water. Industrial sites are also at risk of submergence, which can cause contaminants that are toxic to the environment and human health to be released.
