MACKENZIE, Alison, R. - 2007
The Potential of Using Managed Realignment to Mitigate Sea Level Rise in the Cornwallis Estuary
Coastal regions have become increasingly vulnerable to erosion, flooding and inundation as a result of a global rise in sea level. Sea level in Maritime Canada are expected to rise on the order of 30 – 40 cm per century and when combined with the characteristic high tidal range within the Bay of Fundy, could translate into extensive dykeland flooding with the economic loss of valuable land parcels within the region. At present, a system of dykes protects MMRA land within the Cornwallis estuary however the long-term sustainability of these dykes to mitigate the impacts of accelerated sea level rise is questioned. Two separate flooring scenarios were devised: (i) when no modifications are made to the existing dyke infrastructure and the dykes are allowed to breach, and (ii) when the dyke infrastructure is raised and extended where necessary to accommodate a maximum tide record of 8.87 meters (29.1 feet). The analyses of the flooding scenarios were conducted within the GIS and the area flooded (m2) and the value of land ($/m2) was quantified. The results show that a large proportion of MMRA land (98.6%) and building variances (85.4%) are flooded under the first flooding scenario with a total economic loss of $140,877 x 103 and $33,410 x 103 respectively. In contrast, under the second flooding scenario, a small proportion of MMRA land (0.04%) and building variances (0.0007%) were flooded with a total economic loss of $45. Overall, it is more cost-effective to top-up and extend the dyke systems in the Cornwallis estuary than to allow the land to revert back to the sea. Managed realignment including salt marsh restoration is evaluated for its potential use within the Cornwallis estuary and recommendations for its implementation as a viable long-term mechanism to mitigate the impacts of sea level rise are provided.