CHATHAM — Environmental technicians found themselves up the creek last week, looking at marsh grass and other vegetation.
Consultants from the Horsley Witten Group spent Thursday and Friday examining and photographing the vegetation just inside Muddy Creek as part of an effort to track changes in the waterway's flora following the installation of the Route 28 bridge two years ago.
While the results from the survey won’t be available until early next year, Natural Resources Director Robert Duncanson said there won’t be any surprises.
“It was pretty much what we expected,” he said. As predicted by the study carried out 10 years ago, some of the marsh grasses on the banks of the creek have died off “because it was more freshwater-type vegetation,” he said. Over time, those plants will be replaced with other species that are more tolerant of salt water.
While the changes aren’t very obvious in that part of the creek visible from Route 28, that’s because of the fairly steep river banks, which have narrow zones of marsh vegetation, Duncanson said. Nearer the creek’s headwaters, the shoreline is flatter and larger areas of freshwater flora are dying back, part of the waterway’s natural transition back to a saltwater system.
“Salt marsh has a higher ecological value to many groups, organizations and agencies than freshwater marsh does,” he said. Salt marshes are one of the richest ecosystems on the planet, but they are also very sensitive to changes in water quality.
The river was traditionally tidal until the causeway was built at Route 28, replacing bridges that tended to wash away in storms. The causeway included narrow culverts, which restricted tidal flow in the estuary, which in turn allowed the accumulation of nitrogen from the groundwater, degrading water quality. The bridge built in 2016 had the goal of restoring the original tidal flushing, and monitoring changes in vegetation is one way of judging the project’s effectiveness.
The vegetation survey was required by the agencies that permitted the bridge project.
“It’s also confirmation of the predictions and the expectations that were made 10 years ago when we first did the vegetative analysis of what [species] were there,” Duncanson said. “We’re seeing what we predicted we’d see.”
Though wildlife adapts quickly to change, the shift in Muddy Creek’s ecology from a brackish system to a mostly saltwater one will be gradual, Duncanson said. The creek has a “mucky” bottom covered in organic material, and it will take years for that to dissipate, he said. Until that happens, the creek will not provide good habitat for shellfish, with the exception of the existing sandy shoal just inside the bridge, Duncanson said.