Coastal Engineering Experiences and Approaches in Defining Setback Lines for Shore Protection

Setback lines have become a relevant tool for coastal zone management, protection and adaptation to sea-level rise. The methods and tools used for defining setback lines, however, vary widely from one jurisdiction to another.... [ view full abstract ]

Setback lines have become a relevant tool for coastal zone management, protection and adaptation to sea-level rise. The methods and tools used for defining setback lines, however, vary widely from one jurisdiction to another. They range from predefined, uniform limits to resilient boundaries that are based on the anticipated evolution of coastal processes active along the shoreline. While the former are easiest to implement and regulate, the latter generally provide more pragmatic limits by taking into account site-specific historical records, as well as the local effects of various coastal features that can influence recession rates. In this presentation, we intend to showcase some of the tools and methods used in coastal engineering applications for defining setback lines. Three case studies will be presented involving projects recently completed for Parks Canada in Prince-Edward-Island and Quebec (Gaspésie), which focused on assessing the vulnerability of coastal roadways and developing remedial options. The selected approaches include geomorphological characterizations of the coastline, short-term and long-term modeling of coastal processes and shoreline evolution, as well as empirical methods to account for the effects of sea-level rise. The case studies will also present some of the data requirements needed for performing the analyses, as well as the uncertainties and limitations that remain and which must be considered when assessing the ramifications of these lines. Site features and experiences unique to each project location will serve to highlight some of these challenges, as well as the implications they had on the conceptual solutions that were developed.