In response to a history of flooding affecting adjacent communities, the U.S. Army Corps of Engineers partnered with the City of Alexandria and Arlington County during the 1970s and early 1980s to build a flood control channel in the lower portion of Four Mile Run. The flood control channel has safely conveyed the high storm flows through the two jurisdictions. When the Corps conceived the channelization project in the 1960s, the sole objective of the project was flood protection and, in this respect, the project has been a success; no floods have breached the banks along the 2.3-mile channel since its construction. Although successful in flood control, however, the channelized portion of Four Mile Run leaves much to be desired in terms of aesthetic and environmental attributes.
With this knowledge and a joint vision of Four Mile Run becoming a community amenity, the City of Alexandria, Arlington County, and the Northern Virginia Regional Commission worked closely with a Joint Task Force of community members to develop the The Four Mile Run Restoration Project Master Plan in 2006. Through the support of Congressman James Moran, Congress appropriated funds for the U.S. Army Corps of Engineers to conduct a feasibility study for the entire Four Mile Run watershed and for State and Tribal Assistance Grants for wetland and streambank restoration in both jurisdictions.
A major objective of the Master Plan is to reestablish the vegetation that once lined the stream and existed in the lowland wetlands areas but has since disappeared or been colonized by invasive species. The Four Mile Run Wetlands Restoration, completed in December 2015, plays a prominent role in regional efforts to protect the Potomac River basin and the endangered Chesapeake Bay by restoring the natural cycles and diversity of habitat to support a variety of life in and along these waterways. The Restoration project restored the historic 2-acre tidal wetland where the water levels fluctuate with the daily tidal cycle along Four Mile Run. Wetlands were once common along all the tidal tributaries and protected shorelines of the Potomac River, but many tidal wetlands have been lost to urban and suburban shoreline development. The upland trail serves as a buffer between the tidal wetland and the existing forested wetland. Wetlands are important to both wildlife and humans and provide a connection between aquatic and terrestrial habitats that is important to fish and aquatic organisms as well as many birds and terrestrial animals. Tidal wetlands are important nurseries and foraging areas for fish, waterfowl and other birds, reptiles and mammals. Wetlands also benefit humans by improving water quality and storing floodwaters.
Tidal wetlands can be divided into different plant zones based on fluctuating water depths. This created wetland includes a low marsh zone and a high marsh zone and is surrounded by an upland meadow.
The low marsh zone is typically flooded for more than ½ of the day by water up to several feet deep. This extensive inundation limits the diversity of plants that can grow in this zone. Common low marsh plants, such as the yellow pond-lily (Nuphar advena) and the arrow arum (Peltandra virginica), provide cover for juvenile and adult fish and other aquatic species. The ten-foot tall, emergent grass, wild rice (Zizania aquatica), was an important food crop for Native Americans and remains an important food source for water fowl. The prolonged and deep inundation by tidal waters allows the low marsh vegetation to take up nutrients and trap sediments from the flood waters.
The high marsh is flooded less than ½ the day by water that is typically less than one-foot deep. The vegetation community is composed of many species that form a dense cover. Grasses, sedges and rushes, such as rice cut grass (Leersia oryzoides), soft rush (Juncus effusus), woolgrass (Scirpus cyperinus) and three-square (Schoenoplectus pungens) are common in the high marsh, as are forbs such as rose mallow (Hibiscus laevis), broadleaf arrowhead (Sagittaria latifolia), and swamp milkweed (Asclepias incarnata). The diverse plant community provides habitat to many insects, amphibians, birds and other animals. The high marsh is not inundated for long periods, but the dense vegetation is efficient at capturing sediments and pollutants from floodwaters.
The upland meadow is a perennial herb community that is not regularly flooded. It provides terrestrial habitat utilized by many of the same species that live in the wetland; frogs forage in the meadow and turtles nest here. A mix of grass species and flowering herbs, such as black-eyed Susan (Rudbeckia hirta) and goldenrods (Solidago spp.), provide foraging and nesting habitat for many song birds and provide nectar and act as larval hosts for native pollinators while providing cover habitat for other wildlife. The meadow vegetation also provides soil stabilization and erosion control.
New wetland plantings include:
For questions on the overall project, please contact Dana Wedeles, Park Planner, firstname.lastname@example.org or 703-746-5491
All restoration plans meet USACE approval.For additional Project background and information visit the Northern Virginia Regional Commission's website.