The watershed of Sligo Creek, a tributary to the Northwest Branch of the Anacostia River, is one of the County's most urbanized watersheds. It is also the location of extensive efforts to restore an urban stream system and is notable for the success being achieved in controlling urban stormwater runoff and reestablishing a viable biological community. Until just recently, the only fish identified in Sligo Creek were blacknose dace, goldfish, and creek chub—species that are highly tolerant of polluted urban conditions. External anomalies found in the fishes sampled, particularly the creek chub population, could be associated with environmental degradation such as chronic, sublethal exposure to contaminants or high levels of suspended solids. Many watershed residents are familiar with the signs once posted throughout the watershed, particularly in the lower reaches, warning of polluted water conditions.
Many high-density commercial and residential areas are located in the Sligo Creek watershed, including the Wheaton Triangle area and part of the Wheaton Central Business District, large areas of Takoma Park, and much of downtown Silver Spring. These areas and surrounding residential neighborhoods developed rapidly during the 1950s and 1960s, before today's environmental standards for stream valley protection and stormwater management. All that remains of Sligo Creek's natural stream network are mainstems of streams; most feeder tributaries have been paved over and piped into storm drains. The remaining stream system has been heavily armored in many areas to reduce channel erosion. These alterations might improve bank stability, but they provide limited habitat value. Areas that have not been armored exhibit varying degrees of bank instability and erosion problems due to uncontrolled storm flows. Efforts to restore the watershed have included an examination of methods to improve flow conditions so that stream channel restoration efforts can occur, rather than completely armoring the stream and displacing all natural habitats.
New runoff controls at the Wheaton Branch, University Boulevard, and Sligo Golf Course retrofit ponds, as well as improvements to the aged and leaking sanitary sewers, are bringing positive changes to the streams. Since completion of the Wheaton Branch pond and associated stream channel restoration, native fish have been transplanted from other similar watersheds to augment the recovery of fish populations in Sligo Creek. Existing downstream blockages restrict normal fish movement in the creek to some degree, preventing the natural reestablishment of a more diverse fish community. Biological monitoring conducted by the Interstate Commission on the Potomac River Basin (ICPRB) indicates that the number of native fish species reestablished in the Upper Sligo Creek mainstem has increased from 3 in 1988 to 11 currently. This is extremely encouraging.
Despite the onslaught of urbanization, the Sligo Creek stream valley park system has preserved a riparian corridor that allows the protection and restoration of pockets of high-quality stream habitat. Flow conditions and impaired habitat, which have prevented a viable biological community from living in the watershed, are being addressed through joint efforts by the Department of Environmental Protection, the Maryland-National Capital Park and Planning Commission, the ICPRB, and the Metropolitan Washington Council of Governments as part of the regional Anacostia Watershed Restoration Project. Community groups and schools frequently contribute to efforts to clean up streams throughout the watershed. The Sligo Creek stream valley is heavily used by local residents and visitors, and it is one of the County's most important urban natural environments. The successes achieved thus far in Sligo Creek are setting the standard for other urban watersheds in and beyond the County, and they reflect Montgomery County's emerging national leadership in stream restoration.
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Sligo Creek Stream Condition, Habitat Conditions, and Management Category Designation
|Subwatershed: Stream Condition
||Primary Factors Affecting Stream Condition
||Unique Characteristics and Management Designation|
|Wheaton Branch - FAIR (preliminary)
||This tributary drains the Wheaton Central Business District; high imperviousness, channel alteration, and urban pollutant loads heavily impact the stream system.
An innovative stormwater retrofit project on Dennis Ave. has improved conditions dramatically and allowed stream restoration to occur downstream despite highly urban conditions.
|The Wheaton Branch stormwater retrofit project has been instrumental in achieving improvements in the biological community in Sligo Creek. Fish communities have been reestablished, and downstream of the Wheaton Branch pond, in-stream habitat restoration, riparian vernal pools, and microhabitats supporting amphibians can be observed. |
Watershed Restoration Area
|Upper Sligo - POOR (preliminary)
||Upper Sligo - POOR (preliminary) FAIR to GOOD Overall
||High imperviousness from high-density residential and commercial areas and channel alteration affects flow conditions and habitat. Embeddedness levels are particularly high and banks are unstable in some areas.
||A stormwater retrofit project has been undertaken at an existing pond above University Blvd. to improve runoff conditions from this part of the drainage.|
Watershed Restoration Area
|Middle Sligo - FAIR (preliminary)
||Channel alteration and marginal riparian zone influence habitat conditions, as well as urban runoff conditions typical throughout the watershed. However, this section directly benefits from the upstream improvement in flow conditions associated with the retrofit pond on the Wheaton Branch tributary.
||A highly successful habitat improvement project is located in this section just above Forest Glen Rd. A shallow marsh has been created to replace wetland habitat and treat small amounts of road runoff, while simultaneously preserving tree canopy.|
Watershed Restoration Area
|Lower Sligo - POOR (preliminary)
Flora Lane Trib. - FAIR
|This section exhibits many of the same problems found throughout the watershed, particularly channel alteration and riparian zone impacts.
||Several stormwater retrofit and stream restoration projects are being implemented in this section, including a pond on the Sligo Golf course that will improve runoff from the beltway and upstream development. A unique tributary is also found on the west side of the stream which, owing to discharge from an underground spring in a Metro tunnel, has a relatively cool, clean baseflow source. A structure has been placed in the top section of this tributary to bypass stormflows around the tributary, creating "refugia" to which organisms can retreat during storm flows. Watershed Restoration Area|
|Long Branch - POOR (preliminary)
||Reconnaissance indicated problems with sediment deposition and embeddedness
||Watershed Restoration Area|
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Sligo Creek Watershed Management Category
Watershed Restoration Area: All of the Sligo Creek drainage area is designated as a Watershed Restoration Area. Efforts continue to implement phased retrofit projects throughout the watershed, and activities are ongoing to monitor the success of the fish reintroduction activities that have occurred over the past several years. Current monitoring results show that the reestablished fish community is thriving, and the first signs of successful reproduction are being seen in the 1996 data.
The Sligo Creek watershed has been targeted as an important part of the overall Anacostia watershed restoration effort and has been the focus of efforts to control urban pollutant loadings and restore habitat conditions where possible. There were several unique opportunities within this watershed to modify two older flood control facilities and improve runoff controls in this heavily urbanized area. Stormwater flow control has been improved at these sites, and water quality controls are being added to reduce urban pollutant concentrations. The ability to achieve flow control has allowed successful stream restoration activities to occur in stream segments where they would otherwise have been infeasible due to very high runoff velocities.
Efforts to control urban runoff in this watershed are limited by the small number of feasible opportunities to modify old flow control structures or to establish new stormwater runoff controls at strategically located sites. Large areas of the watershed remain uncontrolled. To ensure lasting success in reestablishing a viable biological community, strong local stewardship of this watershed must become a central part of the daily activities of watershed residents and businesses.
- Implementation of a strong public education program to inform residents about watershed conditions, including pollution prevention education for residents and businesses.
- Continued implementation of Capital Improvement Program stormwater retrofit and stream restoration activities
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Forest Estates Low Impact Development Project
Godwin Marsh and Beltway East Stormwater Management Wetland Creation in the Sligo Creek Watershed (PDF, 2 pp, 404K)
Sligo Creek Recreation Center Low Impact Development (LID) Project (PDF, 2 pp, 607K)
Will be updated.
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