Editor’s Note: This is the third in a series of posts about how the communities of Plymouth and Ludlow restored areas devastated by Tropical Storm Irene and created more resilient rivers, lakes, and wetlands. We thank intern Sarah Kwiatkowski for researching and writing the series.
As Tropical Storm Irene’s waters raged though Money Brook ravine, massive eroded sediment was transported down the steep mountainside, and dropped at the undersized Route 100 bridge. The relatively flat plane that abuts Money Brook and Route 100, known as Pingree Flats, is an alluvial fan—a geologic feature which can occur where a very steep mountain stream transitions abruptly to a flat, broad valley.
Unfortunately, homes and outbuildings on Pingree Flats were destroyed when Tropical Storm Irene brought water and debris to the area. The floodwaters deposited sediment 18 to 24 inches deep in and around the destroyed buildings. As cleanup began, the Lake Rescue Association (LRA) and the Department of Environmental Conservation realized the storm waters had dropped the majority of sediment at Pingree flats, instead of transporting it downstream to Lakes Pauline and Rescue and Round Pond. Since the likelihood of additional flooding remains extremely high, local partners decided to explore how this alluvial fan could be used to catch sediment runoff from the Money Brook ravine.
Previous soil surveys by LRA had determined that Pingree flats was comprised of hydric soils which are most frequently found in wetlands. In the years since Tropical Storm Irene, native low bush willows and other water-loving vegetation had taken root in Pingree Flats. This indicated that the hydric soil was saturated at least part of the year, and the flats could support a naturalized wetland.
Once the high armored banks were flattened, and Money Brook was given room to maneuver, the brook cut a new channel into the revegetating Pingree Flats where it has room to disperse flows and filter water naturally. Observations during Tropical Storm Irene showed that wetlands can help lessen impacts of flooding by storing and delaying passage of water. If restoration of the Pingree Flats wetland continues, and the new channel remains, impacts from the unstable Money Brook ravine would be naturally reduced when future high water events occur.