The headwaters of the stream originate in the city of Rockville, and the branch flows southwest for 11.2 miles (18.0 km),[1] under the C&O Canal near Swain's Lock, to the Potomac River, which drains to the Chesapeake Bay.

[3] While some parts of the Watts Branch watershed are parkland or remain forested, the area is adjacent to Rockville town center and the Interstate 270 corridor.

Population in the Rockville city limits (of which only a portion is in the Watts Branch watershed) more than doubled between 1960 and 2010, from approximately 26,000 to 61,000.

[4] These development trends have led to degraded water quality due to stormwater pollution in some portions of the Watts Branch mainstem and tributaries.

The stream and watershed have been the subject of extensive studies and planning by Montgomery County and the City of Rockville.