The Buzzards Bay Project National Estuary Program has produced an inventory of tidally restricted salt marshes in nine towns within the Buzzards Bay watershed. The Atlas, currently in draft form, identifies tidal restrictions and prioritizes sites for remediation. The Buzzards Bay Project plans to use this document to help initiate salt marsh restoration projects, especially in areas where future road or bridge work is proposed. In many cases, tidal flow can be restored to degraded marshes simply by removing the restricting feature or by increasing the size of the structure to accommodate a full tidal flow.
Tidal restrictions can occur when roads and railroads are constructed over tidal creeks.
Bridges and culverts are commonly installed to allow the movement of tidal waters. However, these structures are often too small to pass full tidal flows necessary to maintain natural salt marsh vegetation upstream. These hydrologic changes can cause a once-saline environment to become brackish or even fresh. Decreases in salinity cause a change in plant species, with native salt marsh grasses and rushes being displaced by upland or freshwater species. One common example of an adverse change in vegetation is growth of the common reed, Phragmites australis.