October 2017, a storm generating high tides and large surf on the south shore of Nantucket caused the erosion of the dune at southern end of Hither Creek. The dramatic erosion led to extensive washover from the Atlantic Ocean which deposited a lot of sand into Hither Creek and on top of surrounding wetlands. Prior to the storm, the southern end of Hither Creek, past Millie’s Bridge, consisted of a deep almost circular salt pond (Millie’s Pond) surrounded on three sides by well-established salt marsh, shrub wetland and coastal shrubs. Following the storm, sand from the eroded dune was displaced onto the salt marsh and filled in a significant portion of Millie’s Pond. Once the storm subsided, the washover ceased and normal tidal flows connecting Hither Creek to Madaket Harbor resumed. While Millie’s Bridge itself remains stable, the vegetated coastal wetland, salt marshes, dune and coastal pond were all dramatically altered.
Salt marshes typically respond well to small amounts of sand deposition (~1-2 inches) but little research has document salt marsh vegetation response to large sand depositions. The Foundation begin a project to monitor vegetation communities impacted by this severe storm event. Monitoring the sand extent and vegetation communities for the first year (Oct 2017 – Oct 2019) has shown that the ecology in this spot has likely been permanently altered. The majority of salt marsh and shrub wetlands surrounding Millie’s Pond have been lost due to the sand burial. The bare sand is beginning to be colonized by plants from outside seed sources but the vegetation communities will likely never be the same.
Over the first year, the sand at the site migrated, filling in more of Millie’s Pond although sand drift fencing installed at the top of the remaining dune has been instrumental in helping retain and rebuild the dune sand. Native dune vegetation is recruiting on the exposed sand, including a state-listed plant of special concern. The exposed sand has also provided habitat to a wide variety of wildlife from shorebirds (including a piping plover pair), fiddler crabs and mating, egg laying horseshoe crabs. If this area is not further impacted by severe storms in the next 3-5 years, a new bordering wetland vegetation community as well as stabilized dunes will most likely establish. The Foundation plans to continue monitoring the sand extent, vegetation communities and dune establishment over time. Undertaking this monitoring is giving us a better understanding of how other marshes on Nantucket may respond to similar events, since storms of this intensity and magnitude are predicted to increase in the future due to the impacts of climate change.