Sandy barriers, climate change and long-term planning of strategic coastal infrastructures, Îles-de-la-Madeleine, Gulf of St. Lawrence (Québec, Canada)

The case study of Îles-de-la-Madeleine is presented to illustrate one aspect of the challenge facing coastal communities with regard to relative sea-level rise and climate change, namely the management of strategic infrastructures located within the coastal zone. GIS mapping has been carried out in two sites where the main road system of this archipelago, Highway 199, is located on sandy barriers and where the road has been threatened by chronic erosion problems for several decades. Our results confirm the dynamic nature of the barriers components (habitats, inlets and tidal deltas) and document the impacts of road-related modifications to the coastal system. These alterations have resulted in significant changes to coastal habitats, including loss due to coastal squeeze between the retreating shoreline and the coastal protection structures. Resort to riprap structures also impacted the evolution of the coastline and further coast hardening might jeopardize the morpho-sedimentary equilibrium of the barriers. To ensure the sustainability of coastal resources and secure Highway 199, it appears that a change is required, from an ad hoc type of management of coastal erosion towards the inclusion of the management of the road system within a long-term and integrated planning of the coastal zone.