|Total Area: 26,696 acres (41.7 mi2)
Average Imperviousness: 19%
Population Density: 4,556/mi2
Wetlands: 337 acres
Forest Cover: 31.3%
Deciduous: 5,611 acres
Coniferous: 775.9 acres
Mixed: 2,922 acres
Shrub/Scrub: 1,072 acres
|Local Watershed Group: The Neighbors of Northwest Branch|
The Northwest Branch is one of two major free-flowing tributaries to the tidal Anacostia River. Its confluence with the Northeast Branch, north of the town of Bladensburg, forms the tidal river. The subwatershed boundaries of the Northwest Branch are generally outlined by Olney-Sandy Spring Road to the north, New Hampshire Avenue and Adelphi Road to the east, University Boulevard and Georgia Avenue to the west, and the southern edge of Hyattsville to the south. Seventy-four percent of the subwatershed is in Montgomery County, with 18% and 8% in Prince George's County and the District of Columbia, respectively. Major Northwest Branch tributaries include: Batchellors Forest tributary, Sandy Spring tributary, Old Orchard tributary, Bryant's Nursery tributary, Longmeade tributary, Rolling Stone tributary, Bel Pre Creek, Sherwood Forest tributary, Glen Allen tributary, Lamberton Drive tributary, Oakview tributary, Adelphi Road tributary, Chillum Road tributary, and Arundel Road tributary.
Dominant Land Uses: The largest land uses, by area, in the Northwest Branch subwatershed are residential (52%) and forest cover (22%); agricultural land use and parkland comprise 9% and 7%, respectively.
Physical Characteristics: The Northwest Branch subwatershed is approximately 26,696 acres (41.7 mi2) in size and approximately 19 percent impervious. Elevations range from 566 feet at the Northwest Branch/Patuxent River watershed divide to 6 feet at the confluence with the Northeast Branch. With an average gradient of 0.60 percent over 15.7 miles of the main stem, Northwest Branch flows from its headwaters in the Piedmont physiographic province, through the Fall Line, into the Coastal Plain. 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 a barrier to the upstream migration of anadromous fish species such as Alewife and Blueback herring. The highly scenic and rugged Northwest Branch Fall Line extends from U.S. Route 29 downstream to approximately Riggs Road (MD Route 212) and the historic Adelphi Mill.
Biological Characteristics: As previously noted, the Northwest Branch subwatershed includes both MDE Use IV and Use I stream designated areas. Major post-1989 restoration efforts in the subwatershed, which have included controlling stormwater quantity and quality, restoring both tributary and main stem instream habitat, fish barrier removal and/or modification, creating and restoring wetlands and riparian reforestation, have resulted in aquatic habitat rankings which are still only partially supporting of reference conditions. In general, the aquatic community present in the upper Northwest Branch is correspondingly healthier and more diverse than that found in the middle and lower portions of the subwatershed (Figures 9 and 10). Main stem macroinvertebrate populations typically remain impacted, scoring no better than 3.3 out of 5.0 points (fair range). It should be noted that the six-lane Inter County Connector (ICC) is presently under construction and that the road's alignment takes it across the more environmentally sensitive headwaters portion of the Northwest Branch.
Condition Summary: The Northwest Branch, especially the upper headwaters portion, is one of the less densely urbanized subwatersheds within the Anacostia watershed. As of 2005, approximately 90-95 percent of the total subwatershed area had been developed. In addition, roughly 31 percent of the subwatershed remains forested. The majority of the upper and middle main stem and tributary portions of the stream are bordered by a broad buffer of parkland owned and maintained by the M-NCPPC; whereas, a narrower 35-50 foot buffer is generally present along the lower main stem between Riggs Road and Queens Chapel Road. Downstream of Queens Chapel Road the riparian corridor is virtually all grass because of floodway-related tree restrictions. In total, approximately 45 percent of the stream mileage present in the subwatershed has an adequate riparian forest buffer (i.e., 300-foot total width), which is confined almost exclusively to the upper two-thirds of the subwatershed.To get involved in protecting your Anacostia subwatershed contact The Neighbors of Northwest Branch.