Returning the tide to dikelands in a macrotidal and ice-influenced environment: Challenges and lessons learned

Abstract

The objectives of this chapter are to (1) document lessons learned from the design, implementation and monitoring of a salt marsh restoration in the upper Bay of Fundy, Canada, and (2) consider how the lessons can be applied to future restoration projects. The Fort Beauséjour salt marsh restoration sites are exposed to very large tides (up to 14 m), waves, and snow and ice in winter. This project involved a managed re-alignment, with two restoration cells and two reference sites. Before breaching, design criteria were established (e.g., the restoration cells must fully flood at high tide and drain slowly) and a hydrodynamic model was used to test breaching options. Pre-restoration monitoring was completed in 2009–2010, the old dike was breached in October 2010, and post-breach monitoring commenced thereafter. Measurements of water level, velocities, and discharge at one breach, compared very well to model predictions. Likewise, patterns of sediment deposition were as predicted, and sedimentation rates were as expected based on empirical studies done in the area. The bioengineering species saltwater cordgrass (Spartina alterniflora) took 2 years to colonize the cells; it initially spread vegetatively and then by seeds. Plant cover became extensive in year 5 post-breach. Invertebrate and salt pool biological communities are lagging behind. Lessons learned include: (1) plan for future conditions and provide adequate accommodation space for development of a new marsh; (2) multi-level partnerships are critical to the success of such projects; (3) monitoring with a research focus ensures observation and quantification of unexpected phenomena; and (4) the design process used, including the hydrodynamic model, was successful and can be used again for similar situations.