Coastal erosion is a natural cycle of sediment motion that is caused by the combined action of the sea and climate factors such as water levels, ice conditions, storms, precipitation, and freeze-thaw cycles. In the St. Lawrence estuary and gulf, this phenomenon appears to have increased in recent years, posing a threat to transportation activities and infrastructures along the coast. The intensification of coastal erosion was documented and, according to the Chaire de recherche en géoscience côtière of the Université du Québec à Rimouski (UQAR), 60% of the coasts of the St. Lawrence estuary and gulf are eroding.
Coastal areas are critically important from a social, economic, and environmental perspective. They are the preferred sites for human settlements, and therefore, activities and infrastructures related to transporting people and goods are an essential service in these regions.
A Serious Threat
Climate change could lead to an increase in the number and intensity of storms, and to rising sea levels. These factors could lead to more coastal erosion.
Experts agree that coastal areas are particularly sensitive to climate change. The expected rise in average temperatures will cause glaciers to melt and oceans to expand thermally, which will raise sea levels. The Intergovernmental Panel on Climate Change (IPCC) predicts that the average planetary sea level will rise by 65 centimetres by 2100.
Higher temperatures also impact waves, winds, and tides. The duration and thickness of ice cover could be affected as well, and an increase in the number and intensity of storms is expected.
All of these phenomena create more problems related to coastal erosion in some areas. Flooding and landslides could also become more common.
Coastal infrastructures are particularly vulnerable to climate change. In Québec, Gaspé, the North Shore, and Îles-de-la-Madeleine will be affected the most.
Damage to Highway 132 in Gaspé can be significant during extreme weather, such as severe storms, as was the case in La Martre in December 2000. A section of Highway 132 more than one kilometre long was completely washed away by the sea during a storm.
The stretches of road that are vulnerable to coastal erosion in the Gaspé and Îles-de-la-Madeleine have been identified, and are the focus of monitoring, and also of special research projects in some cases.
On the left, viewed from the west, are a wooden retaining wall and a road section completely destroyed after a storm in December 2000, near the mouth of Rivière à La Martre in Gaspésie.
On the right, viewed from the east, is a detour road developed temporarily after the storm. Vulnerable road sites are being inventoried since 2008 in the Gaspésie-Îles-de-la-Madeleine and Bas-Saint-Laurent regions.
Did you know that...
According to the oceanic models of Golfe du Saint-Laurent, it is projected that, by 2050, the season during which the gulf will be frozen will decrease from 65 days to about 25 days. This will favour greater coastal erosion since ice is known to mitigate wave action caused by winter storms.
As suggested by the Intergovernmental Panel on Climate Change (IPCC), the MTQ's adaptive strategies revolve around protection, accommodation, and retreat.
Integrated coastal management experience shows that adaptation options produce the best results when they involve local residents and decision-makers.
Protective structures such as walls and backfilling require the establishment of design criteria as well as a determination of construction and maintenance costs. However, the design criteria for certain protective structures must be reviewed in order to strengthen them and to better adapt them to the new climate conditions. Protecting infrastructures may be costly and have limited effectiveness in the long-term in a context of climate change
Did you know that...
Most of the damage to coastal protective structures is cause by storms, which are as sudden as they are unpredictable. For example, the passage of Hurricanes Katrina and Rita in 2005 brought violent rains that caused 19 major breaks along Route 138 in the Côte-Nord region, resulting in the temporary closing of road sections.
Once the vulnerable sites have been identified, safety margins and protective zones must be established in order to limit human activities in those areas.
Withdrawal is a proactive form of adaptation. Sometimes moving a road is more efficient that repairing it or protecting the coastline.
Did you know that...
The average cost of moving certain sections of Route 132 is over one million dollars per kilometre, not including the cost of expropriating and acquiring land and the application of measures to mitigate the environmental impacts.
The ministère des Transports du Québec instigated several research projects on coastal erosion aiming to document this phenomenon better and determine the strategies and measures to adapt to climate change in coastal areas. Two of these projects, each lasting three years, were carried out in partnership with the Institut national de la recherche scientifique - Eau, Terre et Environnement (INRS-ETE).
One of the objectives of the project that involves applying geomatic technology to tracking coastal erosion along Highway 132 in Gaspé is to monitor coastal erosion and the behaviour of protective structures along Highway 132 in Gaspé.
High-resolution aerial data (LIDAR and videogrammetry), combined with ground data, will make it possible to model and analyze the areas at risk, map the coast, and optimize decision-making for site monitoring and MTQ work along Highway 132. This project is part of the GÉOIDE network's general research activity.
The study entitled “Étude hydrodynamique, sédimentologique et biologique des sites de Maria, Saint-Siméon, Bonaventure, Newport et Cap-d’Espoir dans la Baie des Chaleurs, Gaspésie” sought to track the evolution of erosion and sedimentation phenomena at four sites located along Route 132 in Gaspésie. Other research projects are under way with INRS-ETE and the Université du Québec à Rimouski.
The MTQ also collaborated with Ouranos on a 28-month research project. This project, entitled “Study of Shoreline Sensitivity and Community Vulnerability to Climate Change Impacts in the Gulf of St. Lawrence”, had the general objective of assessing the main impacts of climate change on the coastal dynamics of the Golfe du Saint-Laurent region and proposing appropriate adaptation solutions. The summary report of the project is available on the Ouranos website.
Finally, since November 2006, the ministère des Transports has been one of the five cosignatory departments associated with the implementation of the Prevention and Mitigation Framework on the Main Natural Risks (erosion, landslides and flooding). The application of this framework involves the sustained coordination of the government and municipal players to establish the basis of the procedures necessary for harmonized risk management and land use management. The gouvernement du Québec has allocated $55 million for this purpose, spread over 5 years. This is a preventive intervention strategy, which is part of a sustainable development perspective, based on partnership and favouring a concerted approach to decision-making. The Prevention Framework, which was to end on March 31, 2011, was renewed until 2013.