Paddle a canoe through the narrow-leaf cattails of Dyke Marsh, just south of Alexandria, and you might hear the chattering song of one of the wetland's few remaining marsh wrens, which weave cattail leaves into globe-shaped nests several feet above the water.

In 1950, 87 singing male marsh wrens were counted in Dyke Marsh. A recent survey detected only seven,
a decline that reflects the dramatic reduction of the largest freshwater tidal marsh on the upper Potomac River.

Between 1940 and 1973, the wetland was extensively mined for its sand and gravel — even after it was ceded to the National Park Service in 1959. In 1974, Congress mandated that the marsh be restored. After nearly 40 years, a final restoration plan


Dyke Marsh map, illustration by Patterson Clark

The once and future wetland

Destabilized by mining, dredging and the removal of a natural breakwater, the marsh continues to recede, losing about two acres every year.

EXTENT OF DYKE MARSH

RESTORATION

Mid-20th-century mining removed a gravel promontory at the southern end of the marsh, allowing storm-driven waves to erode the wetland.

The first phase of a restoration project will probably be funded
by the Federal Aviation Administration as compensation for disturbance of tidal wetlands during construction of a runway at Reagan National Airport.

A proposed 1,350-foot stone breakwater would protect the marsh from storms and encourage the deposition of sediments on the north side of the breakwater, which would slowly rebuild the wetland.

is nearing approval.

Restoration can be expensive and the NPS has a tight budget, so some of the costs for restoring Dyke Marsh may need to come from private donations. Support may also come from dredging companies that are removing material from nearby shipping channels. Rather than haul the Potomac mud miles away for disposal, it may be cost-effective for them to place multi-acre containment cells in lost areas of the marsh and fill them with the dredged material. By doing so, the marsh would eventually regain some of its size.

Manually replanting vegetation would be expensive, but seeds floating in on tidal flows would eventually germinate and establish vegetation free of charge.

Dyke Marsh, illustration by Patterson Clark

Sources: USGS; Brent Steury, Natural Resources Program Manager, George Washington Memorial Parkway; Glenda Booth, Friends of Dyke Marsh; Larry Cartwright; Department of the Interior; Metropolitan Washington Airports Authority