What is that line of rock off the southern end of Dyke Marsh actually doing? If you've walked the Haul Road Trail since 2022, you've seen it. There's a long breakwater, with lower rock sills running north of it. It looks like the finished product of a restoration. It is closer to a seawall for the marsh that's left. The step that would have grown new marsh behind it was proposed and then turned down.
That changes how you read the next few months at the marsh. Fairfax County's 2026 Comprehensive Plan describes the Wellington planning sector, which includes Wellington Estates, as bounded by the Potomac along its entire eastern border. Belle View Boulevard, Westgrove Boulevard, Morningside Lane, Alexandria Avenue and Collingwood Road connect its homes to the Parkway, and bike and hike trails run along it. Dyke Marsh sits on that Parkway corridor, just south of Belle Haven Park. With construction done and no planting phase scheduled, the visible work there this winter comes from Friends of Dyke Marsh volunteers, researchers and bird counters. Most of it is open to anyone with a free Saturday or Sunday morning.
What the Rocks Were Built to Do
The Friends of Dyke Marsh restoration history and its newsletter, The Marsh Wren, lay out the sequence.
- 2014: The National Park Service's plan for the marsh proposed planting an emergent marsh as part of restoration and stabilization. The permitting agencies did not approve that piece.
- February 2020: A 1,500-foot breakwater and an initial sill were completed at the southern end.
- November 2022: More sills were finished north of the breakwater. Coastal Design and Construction built the work, which left one breakwater and five sills meant to protect the marsh from wave action and encourage sediment to build up.
- May 22 to Sept. 7, 2025: Dr. Terrell "Terry" N. Chandler ran a baseline environmental health assessment of the southern marsh for her master's thesis at George Mason University.
- Summer 2026: In the Winter 2026 Marsh Wren, Chandler said she hoped to do further research.
So the rock work handled the defensive half of the plan. The rocks slow the waves that were wearing the marsh away. They don't add new marsh by themselves. Anything green that fills in behind them has to come from sediment buildup, from plants already there, or from whatever planting eventually wins approval.
The Underwater Plant Already Doing the Job
Chandler's team took measurements at the sills, the promontory, the shoreline, Hog Island Gut, the north inlet and the south side of the Haul Road Trail. They looked at water clarity, nitrogen and phosphorus levels, and what new plantings would need to survive. The question was whether parts of Dyke Marsh could support native submerged aquatic vegetation. These are rooted, flowering plants that grow fully underwater, trap sediment, absorb excess nutrients and give fish and shellfish places to feed and grow.
The most common underwater plant in the marsh today is hydrilla, mixed with spiny naiad and coontail. The National Park Service considers hydrilla invasive. Even so, The Marsh Wren's Winter 2026 issue quotes Chandler's assessment:
"hydrilla is currently fulfilling this ecological role at Dyke Marsh. However, encouraging SAV diversification provides for a more stable and resilient response to environmental changes and more diversification up the food chain."
Her conclusions cut both ways. Some areas of the marsh have the water height, quality and clarity native underwater plants need. The marsh doesn't have enough native plants growing to transplant from one spot to another, and its soils need more study. In practice, the water off the Haul Road is being held together partly by a plant the park would rather not have, while the case for native replacements is still being made one field season at a time.
Where the Volunteer Hours Go
Since the construction ended, most of the visible change on land has come from volunteers. On April 18, Friends of Dyke Marsh and the Sierra Club's Great Falls Group planted more than 200 native plants at two spots along the Haul Road Trail, funded by a national Sierra Club grant and donations from newsletter readers. The Winter 2026 Marsh Wren reported that a local teen installed a new bench along the trail in December as an Eagle Scout project. In April, volunteers sampled Quander Creek, which flows into the marsh, and counted 21 non-scud invertebrates and 33 scuds.
Not all the change was planned. The Spring 2026 Marsh Wren described two to three weeks of "snowcrete" in late January and early February that pushed two boats into the marsh and knocked down the osprey platform near the Belle Haven Marina boat ramp. An active nest has since turned up on a nearby "tiki barge." In June, Friends of Dyke Marsh reported two beavers reinforcing a dam south of the Haul Road Trail.
All of this falls in a milestone year. Friends of Dyke Marsh marks its 50th anniversary in 2026, and both houses of the General Assembly approved identical resolutions honoring it: SJ37 from Sen. Scott Surovell and HJ84 from Del. Paul Krizek. This spring, board member Randy Myers was staffing a welcome table on the Haul Road Trail on Saturdays to mark the occasion.
The Winter Calendar at Dyke Marsh
With the big construction finished, the regular schedule is how the marsh gets tended and watched. These are the dates on the books from this week through mid-January, per the Friends of Dyke Marsh events page, Nature Forward and NextGen Birders for Conservation.
| Date | What | Where and when |
|---|---|---|
| Sundays, except the dates noted below | Expert-led birding with Friends of Dyke Marsh | Belle Haven Park south lot, 8 a.m. |
| Sat., Nov. 7 | NextGen Monthly Bird Outing, about a 1.5-mile out-and-back on Haul Road | South Mount Vernon Trail parking lot, 8 to 11 a.m. |
| Sat., Nov. 14 | Invasive plant removal | Haul Road trail entrance bench, 10 a.m. to noon |
| Sat., Nov. 28 | Invasive plant removal | Haul Road trail entrance bench, 10 a.m. to noon |
| Sat., Dec. 12 | Invasive plant removal | Haul Road trail entrance bench, 10 a.m. to noon |
| Sat., Dec. 19 | Washington DC Christmas Bird Count | All day, count circle includes eastern Fairfax County and Alexandria |
| Sun., Dec. 20 and 27 | No Friends of Dyke Marsh Sunday walk | |
| Sat., Dec. 26 | Invasive plant removal | Haul Road trail entrance bench, 10 a.m. to noon |
| Sun., Jan. 3, 2027 | No Friends of Dyke Marsh Sunday walk | |
| Jan. 18, 2027 | Trash cleanup | Details on the events page |
The invasive-plant sessions tie most directly to the restoration story. Volunteers learn to spot the five or so target species, then pull and clip them so native plants have room. Bring gloves, hand clippers and water, and wear long sleeves and pants. The group supplies instructions, trash bags and some shared tools, and asks that pets stay home. If it's raining an hour before a session starts, that session is canceled. Start times can change, so check the sign-up page the morning of.
December 19 Is Count Day
The Sunday walks pause in late December because of the Audubon Christmas Bird Count. Audubon runs the count each year between Dec. 14 and Jan. 5. Dyke Marsh falls inside the Washington DC count circle, which Nature Forward sponsors. This year's count is Saturday, Dec. 19, 2026. The circle covers most of the District, the eastern portion of Fairfax County, and all of Arlington and Alexandria.
Last year's numbers set the benchmark. At the Dec. 20, 2025 count, volunteers at Dyke Marsh recorded 56 species and 1,396 birds. The standouts were a greater white-fronted goose, a Ross's goose and 10 tundra swans flying over the marsh. This year's tally will add another data point to the record of what the protected marsh supports.
To join the count, Nature Forward directs participants to compiler Larry Cartwright at [email protected] or to Pam Oves at [email protected]. For other help at the marsh, Friends of Dyke Marsh asks people to write to [email protected] about the activities they'd like to join.
Before You Drive Over
A few logistics from Friends of Dyke Marsh can save you a cold walk back to the car or a ticket:
- Park in the south lot. From the Parkway, turn in at Belle Haven Park and Marina and take the first left into the lot. The Haul Road entrance is past the bike path on the right.
- Skip the shoulders of Marina Road. According to the Friends of Dyke Marsh parking alert, U.S. Park Police ticket cars parked on either side. Apart from the two marked accessible spaces near the Mount Vernon Trail, only vehicles with trailers attached may park there.
- Watch the weather. Sunday walks are canceled for lightning, ice, or heavy rain or snow.
- Look for the rock line from the trail. At the southern end, the breakwater and the row of sills mark where wave protection was built. Those are the shoreline features from the 2020 and 2022 phases.
If a Sunday walk or a Saturday work day at Dyke Marsh is part of your winter, we'd love to hear what you saw out there. Living near the Parkway means having this marsh close by, and keeping up with its seasons is part of how Lauren Kolazas and the I Heart Fort Hunt community follow life along the river. Let's Connect.
