Habitat Restoration & Protection Database

This marsh was drained for approximately 40 years and by 1980, much of the vegetation had been replaced by a monoculture of common reed (Phragmites australis) except as noted here. Several hundred feet upstream of the culvert that connected this marsh to tidal waters were small pockets of brackish meadow and brackish reed vegetation. A surprising discovery was the presence of salt marsh vegetation in upstream areas especially in the vicinity of the trolley embankment. This 'inverse' zonation of tidal wetland vegetation can be easily explained. The loss of the tide gate in the late 1970s allowed for inflow of tidal water during the summer months. The culvert was sufficiently small to reduce the tidal inflow volumes. The height of high water, even during spring tides, was too low to overflow the creek bank in the southern or downstream marsh. These waters were therefore confined to the channel, flowing northward. High water finally exceeded the tip of the bank in the vicinity of the trolley embankment. With no freshwater tributaries providing a significant source of freshwater, the water reaching the embankment was in the range of 26ppt, which caused a die-back of reed and replacement by salt marsh plants. As in all drained marshes, soil loss and subsidence of the marsh surface has undoubtedly occurred although there are no field measurements to quantify those changes. After 40 years, the main channel, once a 32" wide mosquito ditch, had widened through scour to an average of 15' in the downstream area. Even though the tide gate was no longer present in the early 1980s, tidal flow would be interrupted when the culvert became plugged with flotsam, particularly seaweed after storms. At these times the marsh became non-tidal and during major rainstorms, would accumulate runoff and form an impoundment that at times flooded Route 146 under the railroad bridge. Similar incidents also occurred before the 1980s and the town's temporary solution to this flooding was to uncover the original culvert on the west side of the road to facilitate drainage.