National Park Service Presents Dyke Marsh Restoration Options
Wetland could be gone in 40 years without action.
A crowd of 120 packed the Indigo Landing Restaurant’s meeting room on
Daingerfield Island on May 8 to hear U.S. National Park Service (NPS) officials present four options for restoring Dyke Marsh.
Jon James, acting superintendent for the George Washington Memorial Parkway, the NPS unit that manages Dyke Marsh Wildlife Preserve, welcomed the crowd.
“This is one of the most satisfying aspects of my job, because it is the protection of resources that we manage for the American people,” he said. Congress mandated that NPS restore the wetland, he added, before introducing several speakers who outlined the problems and options.
Melissa Stepford of the NPS told the group that 270 acres were dredged between 1940 and 1972 and that severe erosion is due to both dredging and natural causes like severe storms. She cited a 2011 U.S. Geological Survey (USGS) study that found that more than 25 acres are gone and that erosion averages 6 to 8 feet a year.
According to the USGS, without action, Dyke Marsh could disappear in 30 to 40 years.
Bill Springer, with contractor RK&K, explained that a promontory, which once extended into the Potomac River but was removed by dredgers, protected the wetland and that simulating the promontory with a structure could reduce erosive energy.
He described four options, the first of which would be to let nature take its course to further evolution or “deconstruction” of the marsh. Common to all other three options is building a structure at the site of the former promontory and constructing breaks in Haul Road to re-establish hydrologic connections.
The other three options – labeled minimum, moderate and full restoration
– differ mostly in the extent or acreage of fill that would be placed in the
gouged-out areas. Full restoration would attempt to return the marsh to its 1937 historic limits.
The options are “concepts,” Stepford stressed, “concepts that are not set in stone,” as she urged people to submit comments.
The project’s goals, according to the NPS, are generally to protect the
wetlands, restore ecological functions, reduce restoration and management costs and improve ecosystem services.
The NPS is accepting public comments until June 20 and will then analyze the comments, draft a final plan, hold another public meeting and implement the final plan in stages, contingent on having appropriate fill and funding. The proposals and the comment form are here. NPS staff prefer electronic submissions.
Mail written comments to Superintendent, George Washington Memorial Parkway, Turkey Run Park, McLean, VA 22101; Attn: Dyke Marsh Wetland Restoration Management Plan/EIS. Mailed comments must be postmarked by June 20.
USGS Study, Key Findings
From 1940 to 1972, Dyke Marsh lost around 270 acres of marshland. It is eroding 6 to 8 feet, or 1.5 to two acres, per year a year on average. At this rate, Dyke Marsh will be gone in 30 to 40 years.
Getting rid of the promontory removed the geologic wave protection of
the south marsh that existed back to at least 1864 and altered the size and
function of the tidal creek network. The minimal protection needed to protect and enhance natural deposition includes a wave break in the location of the former promontory.
Dredging of sand and gravel from 1940 to 1972 was a strong destabilizing force, transforming it from a net depositional state to a net erosional state.
Erosion is both continuous and episodic. Dredging made the marsh subject to significant erosion by storm waves, especially from winds traveling upriver. Damaging storms occur approximately every three years.
Read more in the USGS study: Analysis of the Deconstruction of Dyke Marsh, George Washington Memorial Parkway, Virginia: Progression, Geologic and Manmade Causes, and Effective Restoration Scenarios