Dyke Marsh Wildlife Preserve

Located along the west bank of the Potomac River approximately 95 miles from the Chesapeake Bay, Dyke Marsh Wildlife Preserve consists of approximately 485 acres of tidal marsh, floodplain, and swamp forest. Dyke Marsh, which is believed to have formed 500 years ago, is one of the largest remaining freshwater tidal wetlands in the Washington Metropolitan area.

Dyke Marsh provides a habitat for a diverse array of plants and animals. The Haul Roadh Trail is a favorite of area birdwatchers, hikers, photographers, and nature lovers. In addition, the waters in and around the marsh are popular fishing areas. People who explore the marsh by canoe may be rewarded with up-close encounters with the resident wildlife.

What's in a Name?

Dyke Marsh was indeed "diked" at one time. In the early 1800s, earthen walls were built around the perimeter of the marsh in order to create more "fast land" or land not flooded by high tides. These areas were used to graze livestock or grow crops.

Animals of the Marsh

Dyke Marsh provides supports a diverse array of animals. Beavers and muskrat live and play in the marsh. At dusk, little brown bats and red fox begin their nightly forays. Other mammal species observed in the marsh include: cottontail rabbit, gray squirrel, shrews and field mice.

Several species of reptiles and amphibians also inhabit Dyke Marsh. Bullfrogs and leopard frogs are on the lookout for northern water snakes and snapping turtles. During the summer months, painted turtles may be seen on logs absorbing the sun's warmth and a box turtle might be seen roaming the floodplain in search of food.

Perhaps the most common sound heard in Dyke Marsh is the trill of the red-winged blackbird. Commonly associated with wetlands, red-winged blackbirds nest among the cattails and feed on insects and seeds.

Nearly 300 species of birds have been observed in Dyke Marsh Wildlife Preserve. As a result, Dyke Marsh Wildlife Preserve is one of the premier birdwatching spots in the Metropolitan Washington D.C. Area.

Plants, Plants, and More Plants

To date, more than 360 species of plants have been recorded in Dyke Marsh. The dominant species of the marsh itself is the narrow-leafed cattail, which typically develops its characteristic flower spike by June. Other species associated with the tidal marsh include: arrowhead (a.k.a. duck potato), a plant whose starchy tubers are favored by waterfowl; arrow arum, a distinctive plant with large triangular leaf blades; pickerelweed; sweetflag; spatter-pond lily; and northern wild rice, the grains of which are enjoyed by red-winged blackbirds, waterfowl, and people.

The Human Factor

Today, Dyke Marsh is much different than just 50 years ago. Originally, it is believe that the marsh once consisted of 650 acres. Dredging done during the 1950s and 60s led to the current size and configuration of the marsh. Dredging along the outer fringes of the southern part of the marsh resulted in the removal of approximately one-third of the emergent marsh, which was replaced with deep water that reaches 30 feet (9 m) below mean tide level. Even today, visitors can see the impacts of dredging, including shoreline erosion, trash from dredging operations, and deep holes in the marsh which are most visible at low tide.

Exotic or non-native plants are another result of human impacts at Dyke Marsh Wildlife Preserve. Exotic species are very opportunistic, growing in disturbed areas and often out-competing beneficial native species.

Several exotic vines smothering portions of the floodplain forest, including porcelain-berry, Japanese honeysuckle, and Asiatic bittersweet. The marsh is not immune to exotics either. Yellow iris and the common reed are present and efforts are being made to prevent the introduction of purple loosestrife.

A Fragile Habitat

Today, armed with a greater understanding of the importance of wetland ecosystems, we can take steps to protect the fragile habitat that is Dyke Marsh. You can help us to ensure that Dyke Marsh will be enjoyed by future generations. Please:

  • Leave your bicycle in the rack provided at the entrance to the Haul Road.
  • Keep your pets on leashes at all times.
  • Stay on the main trail.
  • Leave only footprints. Take only pictures.

In the News

Dyke Marsh Wildlife Preserve Restoration :The Baltimore District and the National Park Service (NPS), George Washington Memorial Parkway, are working on a project to restore up to 100 acres of freshwater tidal marsh within the 485-acre Dyke Marsh Wildlife Preserve in Fairfax County, Virginia, which is just across the Potomac River from the National Harbor.

Last updated: December 14, 2015

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George Washington Memorial Parkway Headquarters
700 George Washington Memorial Parkway

McLean, VA 22101


(703) 289-2500

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