Assessment of the Approach Used to Design a Salt Marsh Restoration on the Bay of Fundy, NB, Canada and of Overall Project Success from a Geomorphic Perspective

English Abstract:

With rising relative sea level and climate change, restoring a salt marsh as part of a dyke abandonment plan may be desirable in Atlantic Canada in coming years. As a pilot project, a salt marsh restoration on the Bay of Fundy was designed in 2009-2010 and implemented in 2010. Three openings (breaches) were cut in an old dyke to allow the adjacent areas to flood with salt water at high tide. Restoration has been monitored since 2010 and key environmental variables measured. One aspect of the monitoring was to take collected data for sediment deposition, site topography, and water flows through the breaches and in the restoration area, and use them to both improve the implementation of the hydrodynamic model used to design the breaches and to assess the relative success of the design used. Using measured water levels, breach geometry, and site topography, the type of model used to design the breaches was rerun for tide cycles for which flow data were recorded using an acoustic Doppler velocimeter (ADV) and/or an acoustic Doppler current profiler (ADCP). Overall, the results obtained are very promising. The model predicts flows in the restored area reasonably well, especially when a high drag coefficient is used. Correlation coefficients between modeled and measured flow values are generally high. For sediment deposition, the modeled results generally agree with measured results. The model is effective for showing where sediment is likely to accumulate to the greatest degree (i.e., relative deposition). The study confirms that the design approaches taken were sound, effective, and could certainly be used to design a future salt marsh restoration project on the Bay of Fundy.