Looking to the future

Hydrodynamic model run showing water levels (and extent of exposed sandy bottom) during an average low tide under the scenario of maximum possible tidal exchange.

Despite the significant gains in species diversity, water quality, and overall ecological health of East Harbor, impairments still remain. However, these problems need not be permanent - more complete restoration could expand saltmarsh plant communities, eliminate the periods of low dissolved oxygen that impact benthic communities, and reduce the potential for nuisance alga blooms

Modeling more complete habitat restoration

Hydrodynamic modeling (large image) indicates that the maximum degree of tidal restoration that is possible will produce a modest area of exposed sand flats at low tide, indicated by orange and red shades in the above map. Intertidal flats promote the natural setting of shellfish beds.

 

Can this be the future landscape of East Harbor?  Yes, but we will need much more tidal exchange for this to become a reality.

What would happen with increased sea water exchange?

• Flushing rate greatly increases with a larger inlet
• Tidal range increases greatly with increasing inlet width, reaching 41% of Cape Cod Bay tides with an inlet of 50 meters wide.
• Peripheral wetlands and shrublands convert back to salt marsh
• Improved flushing and water quality alleviates some of the problems associated with the current tidal restriction (e.g., macroalgae growth)
• Habitat conditions for finfish and shellfish are further enhanced improving opportunities for recreational fishing and clamming.
• Reduction in algal blooms improves conditions for kayaking and canoeing.
• Development of intertidal habitat provides foraging areas for resident and migratory shorebirds and increases opportunities for wildlife viewing.

In general, the long-term effects of tidal restoration on the local human community and visitors are expected to be positive, with greatly improved water quality and abundant marine resources. That said, the Seashore does acknowledge the possibility that greater tidal exchange might impact barrier beach sediment dynamics along the Cape Cod Bay shoreline (Beach Point area). This issue will be the subject of intensive study and the results will dictate whether further restoration is feasible.

To restore East Harbor back to a healthy, salt marsh lagoon is to restore our natural heritage in this part of Cape Cod.

 

Results of partial tidal restoration

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