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Northwest Branch Subwatershed

The Northwest Branch, in the eastern part of the County, is the largest of the four County subwatersheds that contribute flow into the Anacostia River (Northwest Branch, Sligo Creek, Paint Branch, and Little Paint Branch).

The Northwest Branch of the Anacostia River originates south and east of Olney, MD near the intersection of Route 108 and Georgia Avenue, and flows south approximately 15 miles before passing into Prince Georges County, where it is joined by several other major tributaries to form the Anacostia River.

Tributaries in the upper part of the subwatershed, particularly the headwaters, support the few remaining streams with excellent and good conditions in the Northwest Branch subwatershed.

There are 32 species of fish found in the Northwest Branch including rosyside dace, northern hogsuckers, and five species of shiners. Some species can be found throughout the subwatershed, but others are found only where the right mix of habitat, flow, and low amounts of pollutant stressors occur.

Northwest Branch Subwatershed Study (PDF, 2.4MB)

Image of the stream and trees around Northwest Branch Watershed.


A Journey Through Northwest Branch 



The upper portion of the subwatershed has changed from predominantly agricultural to suburban. As a result of this new landscape, the streams have also transitioned. Tributaries of the Northwest Branch went from carrying sediment and nutrients associated with farming activities to increased levels of stormwater due to development.

As this transition continues, today's environmental standards are designed to minimize the impacts to the streams through forested buffers, floodplain and wetland protection, and management of stormwater runoff. However, with the application of modern stormwater controls, changes in subwatershed hydrology are inevitable.


The middle section of the subwatershed contains a mix of moderate to higher density land uses along with large areas of forested parkland. Inadequate stream buffers on the tributaries are common in this section. More of this area developed with stormwater controls than in the lower reaches.

DownstreamImage of downstream torrent and gorge section of Northwest Branch Watershed.

The lower reaches of Northwest Branch contain older and more concentrated development. These communities developed long before requirements for stream protection or stormwater management. The hydrology in these areas has been altered, and the stream condition is generally poor or fair.

However, also found in this part of the sbwatershed is a stream section described as "the most scenic and rugged section of the Anacostia watershed." This is the beginning of the torrent and gorge section of the Northwest Branch, which begins just below Route 29. This is a transitional area where the Northwest Branch leaves the Piedmont and passes through the fall line before entering the slower reaches of the Coastal Plain. This area contributed significantly to the State of Maryland’s identifying the Anacostia as a state "Scenic and Wild River" in 1984, under the Maryland Scenic and Wild Rivers Act.


How Can I Help Protect the Northwest Branch Subwatershed?

Individuals interested in helping to protect the health of the Northwest Branch can contact the Neighbors of Northwest Branch. This organization of local citizens prides itself in keeping the streams in the Northwest Branch subwatershed healthy and alive for all to enjoy.