4 minute read
Blackwater National Wildlife Refuge Marsh Resiliency
Cambridge, Maryland, United States
Blackwater National Wildlife Refuge (Blackwater) provides three major types of habitat— forest, marsh, and shallow water—to a wide variety of wildlife and plantlife. Since 1938, however, 5,000 acres of marsh has been lost. Models suggest that, as sea levels rise, virtually all of the preserve’s current tidal wetlands in the Chesapeake Bay could erode by the end of the 21st century. Since returning the area to its precolonial state would not be feasible, this wetland restoration project became a small part of the long-term strategy package developed by a partnership of the U.S. Army Corps of Engineers (USACE) Baltimore District (NAB), U.S. Fish and Wildlife Service (USFWS), The Conservation Fund, and Audubon Maryland-DC to ensure that Blackwater’s tidal wetlands endure. The project involved a process called thin-layer placement; this effort marked the first time the process was successfully executed in the Chesapeake watershed. In 2016, sediment dredged from the Blackwater River was placed at a deliberate thickness on 40 acres of marsh surface with the goal of raising the marsh surface to a level necessary for resiliency and for stimulating the growth of native marsh grasses. Based on its effectiveness, significance, and innovation, the Blackwater National Wildlife Refuge Marsh Resiliency project was designated runner-up in the 2017 American Society of Adaptation Professionals Prize for Progress in Adapting to Climate Change.
Article cover: Enhancing Blackwater Refuge wetlands strengthens coastal protection for the area and provides habitat for a variety of species. (Photo by Tim Welp, ERDC)
Producing Efficiencies
Since it was infeasible to bring the refuge back to its precolonial state, the project’s focus pivoted to preserving what was still viable by mitigating the changes that had already occurred and any projected for the future, with respect to sea level rise and subsidence, or sinking of land. For this project, 26,000 cubic yards of clean dredged material from a nearby location, the Blackwater River, was beneficially used for raising the marsh surface through a process called thin-layer placement.
Using Natural Processes
The primary objective of this project, placing sediment to raise the marsh’s elevation by 4–6 inches, will naturally and efficiently deliver a suite of associated benefits to Blackwater’s wetland ecology. Oxygen will more easily reach marsh vegetation’s roots, allowing native grasses to propagate. Healthier marsh vegetation will then be a source of more sustainable bird habitat. The slow disintegration of the marsh’s root zone due to excess water from flooding should reverse, extending the life of the marsh by several decades. The process should transform the site to high marsh habitat, which will also attract the black rail and saltmarsh sparrow.
Broadening Benefits
Known informally as the “Everglades of the North,” Blackwater serves as a buffer for extreme weather events to the town of Cambridge and lower Dorchester County. The area was also designated as a “Wetland of International Importance” by the Ramsar Convention and was named a priority wetland in the North American Waterfowl Management Plan. An Internationally Important Bird Area, Blackwater is home to the largest breeding population of American bald eagles on the East Coast north of Florida. Blackwater is also a habitat for the largest natural population of the formerly endangered Delmarva Peninsula fox squirrel.
Promoting Collaboration
The wetland restoration project is a small part of the long-term strategy package devised by a partnership of USACE NAB, USFWS, The Conservation Fund, and Audubon Maryland-DC, the Town Creek Foundation, and others. The primary goal of the project is to ensure that Blackwater’s tidal wetlands survive as sea level rises. The $1.1 million for this project was funded with federal grants for coastal resiliency projects that were instituted after Hurricane Sandy in 2012.
