Human settlement in environments as dynamic as the coastal zone will inevitably lead to conflict between the natural variability of the coastal environment and the economic, social and cultural activities taking place within it.   In order to mitigate potential negative impacts (e.g. loss of life and infrastructure), managers and planners need to better understand coastal processes and dynamics.

Determination of coastal vulnerability requires an understanding of the interaction between exposure conditions (sea level rise, storm surge, erosion), biophysical state, and resilience of the coastal system.    Resilience refers to the capacity of the coastal system to recover or bounce back from a disturbance event such as a hurricane. Understanding the exposure conditions to current and future climates and biophysical state helps to select nature based adaptation options that are most appropriate for the local conditions. 

Since 2008, we have applied a combination of field based rapid vulnerability assessment tools, local knowledge and geomatics analysis of past rates of coastal change to inform decision making in Atlantic Canada, the Caribbean and the Indian Ocean.  These projects have also included capacity building opportunities for local communities.   Recently, we have conducted comprehensive analyses of the vulnerability of dykeland systems in the Bay of Fundy.

Dykes and Dykeland Communities

Dyking was first introduced to Nova Scotia by the Acadians in the 17th century which allowed them to convert the ecologically productive salt marshes in the Bay of Fundy into usable agricultural land. Today, many of the same areas and Acadian heritage sites are protected behind large, modern dyke and aboiteau systems. These new dykes, built with modern machinery, are much larger and in different locations than the original Acadian ones, but protect much of the same land. Many coastal communities and fertile agricultural land occupy low lying, former salt marsh habitats, now dyked, in the Maritimes.   The dykes were constructed to levels to protect agricultural land with critical elevations dictated by the high water line established in the 1950s and 60s.  While many of these dykes were topped in the early 2000s and critical elevations increased, numerous reports over the last decade have identified that dykes within the Bay of Fundy are vulnerable to overtopping under current and future sea level rise and storm scenarios (Tibbetts and van Proosdij, 2013; van Proosdij and Page, 2012; Webster et al., 2012).  This flooding will directly and adversely affect the productivity of the agricultural land as well as the infrastructure, homes and businesses that have, over time, come to depend on these dykes for protection from coastal waters.  Indirectly, this has an impact on many critical elements of the target value supply chain and economy.  For example, it is estimated that overtopping of dykes at the Tantramar marshlands and flooding of the Trans-Canada highway and CN rail would result in a loss of 50 million dollars of trade per day (Spooner, 2009; Webster et al., 2012).   

With rates of relative sea level rise exceeding 1 m within the next 80 years, high rates of erosion of foreshore marsh in front of the dykes and geotechnical constraints, it will not be feasible in many of these areas to raise all of the dykes to climate change standards.  Provincial officials charged with managing these dyke systems under the Marshland Act need to prioritize which dykes to top and maintain.  This requires a solid appreciation of not only where dykes are vulnerable to overtopping or breaching (failure) but also what the probability is of this occurring, what is being protected and a measure of the ‘urgency to act’. 

Since 2003 we have been actively engaged with the NS Department of Agriculture, Land Protection and relevant stakeholders to support decision making by providing rigorous, scientifically sound assessment of probabilities of dyke overtopping, rates of erosion, modelling the extend of flooding and impacts on infrastructure and communities while suggesting climate change adaptation strategies.  Recently this includes the AgriRisk Project: Risk Proofing Nova Scotia Agriculture (led by NSDA, NSE, and NSFA; funded by Agriculture Canada) and Fundy flood-risk mapping (led by NSDA and NBDA; funded by the National Disaster Mitigation Fund). 

Our academia-industry project team has a particular expertise in the assessment of health and resilience of foreshore marshes that protect our dyke infrastructure and their likely response to climate change and human impacts.    We continue to engage in research that seeks to stimulate the growth of foreshore marsh as a nature-based adaptation strategy and the sustainability of current dykeland management strategies such as use of borrow pits.  We are currently working closely with the NSDA within our Making Room for Wetlands project, developing a framework for and implementing managed realignment in select sites within the Bay of Fundy.