Coastal and riparian municipalities along the St. Lawrence River are exposed to water level fluctuations and shoreline erosion, the frequency and intensity of which are affected by climate change. These hazards are important components of the river system that control the evolution of shorelines and coastal ecosystems, but they pose a significant threat to the built environment and the safety of populations. The project is part of the “fluvial section” component of measure 2.6 of the Quebec government’s 2013-2020 Action Plan on Climate Change (PACC), which aims to support municipalities located along the St. Lawrence facing coastal erosion. In addition, the major floods experienced in various parts of the province during the spring of 2017 and 2019 have highlighted the importance of revising existing planning tools and collecting new data to improve the management of hydrometeorological hazards. This project relied on close collaboration with the organizations coordinating the Regional Round Tables (TCR) in the territory concerned, as well as with the Ouranos team involved in a joint project that is also part of this PACC measure.
Over the past few decades, changes in shoreline land use coupled with increasing river infrastructure have increased vulnerability for communities and ecosystems along the St. Lawrence. Exposure to geohazards is also evolving due to ongoing climate change, highlighting the need for flexible management strategies for riparian environments. In this perspective, GIS-based mapping allows the integration of a wide range of environmental data. However, these datasets are often incomplete and non-homogeneous over large geographic scales, which can be problematic for the implementation of regional land-use strategies.
Using the St. Lawrence Fluvial System (SLFS) (Quebec, Canada) as a case study, this analysis reports and describes a high-resolution approach to mapping the position, characteristics, and erosion susceptibility of natural and artificial stream banks from remote sensing, fieldwork, and local knowledge data. This approach allowed the identification of erosion-prone sites and the identification of dominant erosion processes as well as their spatial constraint along the SLFS. The proposed geospatial framework provides (1) a comprehensive picture of the river landscape that will enable effective implementation of future monitoring and process-based studies; and (2) a first step to support land use stakeholders in selecting appropriate measures to ensure greater resilience of riparian communities and ecosystems.