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Total Area: 7,085 acres (11.1 mi2)
Average Imperviousness: 34%
Population: 81,943
Population Density: 7,081/mi2
Wetlands: 1.5 acres

Forest Cover: 14.9% Deciduous: 826.4 acres
Coniferous: 157.9 acres
Mixed: 758.6 acres
Shrub/Scrub: 368.7 acres
Local Watershed Group: Friends of Sligo Creek

Sligo Creek is a free-flowing tributary of the Northwest Branch of the Anacostia River; the stream joins the Northwest Branch at the western city limits of Hyattsville. The subwatershed is generally bound by Arcola Avenue and University Boulevard to the north and east, Queen's Chapel Road to the southeast, and the District of Columbia and Georgia Avenue to the west. Seventy-five percent of the subwatershed is in Montgomery County, with 20% and 5% in Prince George's County and the District of Columbia, respectively. Major Sligo Creek tributaries include: Wheaton Branch, Flora Lane tributary, Woodside Park tributary, Long Branch and Takoma Branch.

Dominant Land Uses: The three largest land uses by area in the Sligo Creek subwatershed are residential (75%), forest cover (10%), and commercial (8%).

Physical Characteristics: The Sligo Creek subwatershed is approximately 7,085 acres (11.1 mi2) in size and approximately 34 percent impervious. Elevations range from 450 feet at the subwatershed divide to 35 feet at the confluence with the Northwest Branch. With an average gradient of 0.72 percent over 8.3 miles of the main stem, Sligo Creek flows from its headwaters in the Piedmont physiographic province into the Coastal Plain. Average baseflow for the lower Sligo Creek main stem is estimated to be approximately 5-6 cubic feet per second. The Fall Line or Zone represents the transitional area between the Piedmont Plateau and the Coastal Plain. It is characterized by an abrupt change in valley slope, with a corresponding increase in stream gradient, a boulder-strewn appearance, and small to medium-sized cataracts which act as barrier to the upstream migration of anadromous fish species such as Alewife and blueback herring. The entire lower main stem channel, from Riggs Road to the confluence with Northwest Branch, has been channelized. In addition, major portions of the Sligo Creek main stem (from University Boulevard downstream to Maple Avenue) has been armored with rip-rap (i.e., large stone), so as to reduce streambank erosion problems.

Biological Characteristics: Sligo Creek is designated a Use I stream (i.e., suitable for water recreation and support of aquatic life) by MDE. The condition of fish and macroinvertebrate populations in Sligo Creek has improved since the completion of the first two phases of habitat restoration in the upper third of the subwatershed. These efforts, which have included controlling stormwater quantity and quality, restoring both tributary and main stem instream habitat, creating wetlands, reforestation, and native fish and amphibian reintroduction have resulted in aquatic habitat rankings of greater than 70% (partially supporting) of reference conditions at three main stem sampling sites. Although aquatic biota are correspondingly healthier and more diverse than during previous sampling, main stem populations remain impacted, scoring no better than 36% (moderately impaired) of reference conditions. Several physical barriers to both resident and anadromous fish movement and migration are present downstream of Riggs Road. These, as well as other barriers in Sligo Creek, have been identified and remain as a restoration challenge for this subwatershed.

Condition Summary: Sligo Creek is one of the most urbanized subwatersheds within the Maryland portion of the Anacostia watershed. Approximately 90 percent of the total subwatershed area is developed, and only 15 percent of the subwatershed remains forested. The majority of the stream is bordered by a narrow buffer of parkland owned and maintained by the Maryland-National Capital Park and Planning Commission (M-NCPPC). However, only about 35 percent of the stream miles have an adequate riparian forest buffer (i.e., 300-foot total width). Initial indications are that comprehensive stream restoration efforts in the subwatershed, as well as fish re-introduction, have been successful in partially restoring the aquatic ecosystem of Sligo Creek. The impaired condition of the aquatic biota that remains following these efforts are attributable to how recently these projects were completed and the need for additional stormwater management controls and instream restoration work. Planned future projects include, but are not limited to: stormwater management focusing on the employment of low impact development (LID) and environmentally sensitive design (ESD), wetland creation, aquatic and terrestrial habitat restoration, fish barrier modification/removal, invasive plant management, trash reduction and potentially additional fish reintroductions.

To get involved in protecting your Anacostia subwatershed contact The Friends of Sligo Creek.