The Lower Potomac Direct watershed is located in the southwestern
portion of Montgomery County. The watershed has a drainage area
of approximately 61 square miles, and includes the subwatersheds
of Muddy Branch, Watts Branch, Little Falls, and Rock Run. The Lower
Potomac Direct is a highly urbanized watershed with a rich history
dating back to the Civil War era.
Muddy Branch originates in Gaithersburg's historic district, one
of Montgomery County's oldest development centers. The stream flows
southwest for approximately thirteen miles, before flowing into
the Potomac River. Lack of stream buffer and stormwater management
along major transportation corridors such as Route 355 and the railroad
have resulted in high levels of impervious areas in the headwaters,
and have impacted the streams in the upper portion of the subwatershed.
Development occurred at a very rapid pace in this subwatershed,
primarily after the 1970s. These later developments were subject
to some level of environmental standards, but only the most recent
ones have stream buffers and on-site stormwater controls. Closer
to the headwaters, several regional stormwater facilities have been
installed to control areas of high impervious associated with the
Shady Grove research and development and commercial corridor. Large
areas of the stream valley have been purchased as parkland to protect
landowners from flooding and improve stream protection. The lower
development densities and higher level of protection downstream
correspond to improved stream conditions.
Watts Branch originates in the City of Rockville, to the south
and east of the intersection of I-270 and Shady Grove Road. The
stream flows southwest for approximately 11 miles, and merges with
Piney Branch before entering the Potomac River. The headwater areas
are highly developed and contain commercial, high-density residential,
and research and development centers. The upper portion of Watts
Branch has been impacted by runoff from the high impervious areas.
The lower portions of the subwatershed are predominately lower density
residential and still support a diverse fish population. The upper
and western portions of Piney Branch and Lower Sandy Branch, major
tributaries, contain high quality, coolwater streams and are important
in maintaining water quality further downstream in the mainstem.
In 1995, the Piney Branch tributary was designated as a SPA in recognition
of the need to preserve this sensitive resource as its headwaters
were developed. There is an ongoing effort to address water quality
problems in the Watts Branch watershed through additional runoff
control, restoration of stream habitat, and improved stormwater
Subwatersheds Implementation Plan
Muddy Branch and Watts Branch Subwatersheds Implementation Plan (PDF, 32 pp, 1.59 MB)
The Montgomery County Muddy Branch and Watts Branch Subwatersheds Implementation Plan first recommends prioritizing full implementation of high and low priority projects during the County’s MS4 permit cycle through 2015. Fewer additional opportunities exist overall compared to the Anacostia and Rock Creek Watersheds. No other strategies were proposed as there are no existing TMDLs in the Muddy Branch and Watts Branch subwatersheds. In future permit cycles, previously identified stream restoration projects are recommended for implementation for pollutant load reduction.
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