I take walks around Long Bridge Park. If you stand at the southern end of the concrete concourse and look east toward Reagan National Airport, there’s a marsh area. I’ve noticed what looks to be some kind of aquaculture set up: lines strung along the opposite shore with tin foil attachments. I haven’t been able to figure out what that is.

       Support our journalism. Subscribe today. ChevronRight

       — Joe Lowry, Arlington

       It is not aquaculture. There are no fish pens or artificial oyster reefs under the waters of Roaches Run.

       But something is growing down there: plants that the National Park Service hopes will restore the body of water to a more natural state.

       Eight years ago, the Park Service began addressing a problem that’s common to area marshes: the spread of an invasive plant with the rather common name of common reed. The scientific name is Phragmites. You’ve probably seen it around: tall stalks with fluffy seed heads. Thick stands of the aggressive reeds out-compete native plant species. They make it hard for animals — including humans — to penetrate their tight quarters. When they dry out, they can be a fire hazard.

       Advertisement

       Story continues below advertisement

       The Park Service employed herbicide to remove the Phragmites. Then on Jan. 24, 2016, a Dominion Energy transformer in Crystal City ruptured, spilling 13,500 gallons of oil. Most of that was recovered. However, some of it made its way into Roaches Run Waterfowl Sanctuary. An oil sheen was spotted along the Potomac River.

       The spill of medium-weight oil killed about two dozen birds, mostly Canada geese. In the aftermath, money was set aside to restore Roaches Run. Part of the plan involves reintroducing native plant species that are more appropriate to the site than Phragmites: narrowleaf cattail, pickerelweed, black willow, blue iris, buttonbush and alder.

       But there was a problem when the first seedlings went in last year at the southern end of Roaches Run: They were gobbled up. Thus the contraptions that you see: layers of fencing and string. Affixed on top are shiny bits of foil that dissuade birds from landing.

       Advertisement

       Story continues below advertisement

       The contraptions are called exclosures, the opposite of enclosures. Rather than penning wildlife in, the fencing is designed to keep critters out.

       “We’re excluding things that might either flatten it, stomp on it or eat it,” said Charles Cuvelier, superintendent of George Washington Memorial Parkway.

       The animals that nibble from below the waterline include carp and turtles. From above, they include birds such as Canada geese. The field of glittering metal helps.

       “Birds tend not to want to land in an area like that,” Cuvelier said. “They see it from the air and divert to smooth water. It appears to them to be a hazard.”

       The exclosures are a bit of an experiment. More plants went in in the spring. Additional seedlings will be planted next spring, including sticks of willow and alder, their bases treated with a chemical that promotes root growth. The Park Service will check periodically to see what’s thriving and what isn’t.

       Advertisement

       Story continues below advertisement

       “We’re hopeful that in five to 10 years we could see a proliferation of blue iris,” Cuvelier said. “The cattail would be good. The alders and the willows would be a nice improvement.”

       Why bother with all this toil and expense?

       “From a resource management perspective, we try to keep our parks in natural conditions,” said Cuvelier. “This is a reminder of the impact invasive plants can have, and the amount of labor and work required when they cause harm to a park. It’s a good reminder to every one of us that what you plant in your yard may end up downstream. We want to encourage native plants at home and in the park.”

       There’s a second reason: Roaches Run is near Reagan National Airport’s Runway 15-33. Or, rather, the runway is near Roaches Run. (Humans are the planet’s most invasive species.)

       Story continues below advertisement

       “Part of what the airport is mindful of is bird strikes,” Cuvelier said.

       Advertisement

       The plants that are being introduced are not desirable to geese, he said. That should lower the risk to aircraft taking off and landing.

       Why is it called Roaches Run in the first place? “Run” — like “branch” — is another name for a stream. The stream that feeds the lagoon is named for the family of James Roach, who ran a nearby brickworks and owned a mansion, since torn down, called Prospect Hill.

       Any questions?

       Send your questions about the Washington area to answerman@washpost.com.

       Twitter: @johnkelly

       For previous columns, visit washingtonpost.com/john-kelly.