By TIM PURINTON
The Upper North Shore coastline, stretching from Cape Ann to New Hampshire, is well known for its many acres of productive salt marshes. Unfortunately, vast areas of salt marsh are currently being impacted by road and rail crossings which restrict tidal flows to upstream marshes. Regular flushing maintains the health of a marsh, controlling the growth of invasive species such as Phragmites australis and providing habitat for many other species.
Some of the detrimental effects of restrictive crossings include a change in plant species composition, flooding in storm conditions, excessive bank erosion, reduced wetland productivity and diminished nutrient exchange.
One of the Eight Towns and the Bay Committee's most successful demonstration projects from 1997 was the Tidal Crossing Inventory and Assessment Project. It has provided a foundation for ongoing salt marsh restoration projects and has introduced local constituents to an environmental issue that threatens the health of coastal wetlands.
8T&B chose the Parker River Clean Water Association (PRCWA) to prepare a comprehensive report on tidal restrictions, both road and rail, in the 8T&B region. Over 125 crossings were identified and nearly half of them were deemed too small to pass sufficient tidal flow. The report also made recommendations on means of improving tidal flow for each of the most restrictive crossings. This report has already been used by local highway departments, conservation commissions and state agencies to implement measures that will correct restricted tidal flows. Currently, three tidal restoration projects are underway in Gloucester (Long Wharf), Ipswich (Argilla Road) and Essex (Conomo Point Road).
In Gloucester, the Long Wharf crossing was identified as one of the region's most restrictive sites (a tidal crossing that holds back more than five inches of tide during the ebb and flow cycle is considered restrictive). Since the assessment work has been completed, 8T&B Gloucester Committee member Dave Sargent has spearheaded a multi-agency effort that will result in the installation of a large box culvert this spring. The new culvert will reintroduce tidal flow to deter Phragmites australis ("phrags”) and act as a conduit for anadromous fish, specifically alewife. PRCWA utilized volunteers to execute the study, which is now being used as a local and interstate model for assessing tidal restrictions. A volunteer handbook, which was also produced with the support of 8T&B, has been completed by the PRCWA and is available on their Web site <http://www.parkerriver.org/>.
For more information, contact the PRCWA (948-2341). Summary Reports can also be obtained by contacting Vicky Boundy at MVPC.
