Rock Creek (Potomac River)

Rock Creek

Rock Creek, Washington, D.C.
Basin
River mouth Potomac River
0 feet (0 m)
38°53′58″N 77°03′26″W / 38.899556°N 77.0572°W / 38.899556; -77.0572Coordinates: 38°53′58″N 77°03′26″W / 38.899556°N 77.0572°W / 38.899556; -77.0572
Watershed area 76.5 square miles (198 km2)
Cities Rockville, Maryland Washington, D.C.
Landmarks Rock Creek Park
Physiognomy
Length 32.6 miles (52.5 km)
Discharge
  • Average rate:
    63.7 cu ft/s (1.80 m3/s)

Rock Creek is a free-flowing tributary of the Potomac River, which empties into the Atlantic Ocean via the Chesapeake Bay. The creek is 32.6 miles (52.5 km) long,[1] with a drainage area of about 76.5 square miles (198 km2). The last quarter-mile (400 m) of the creek is affected by tides.[2]

Geography

The creek rises from a spring near Laytonsville in Montgomery County, in the U.S. state of Maryland, and joins the Potomac near Georgetown and the Watergate in Washington, D.C. Beginning in the Derwood–Rockville area in Maryland, the creek flows through Rock Creek Regional Park southward to the D.C. boundary. About 9 miles (14 km) of the creek flow though Rock Creek Park in Washington, where it is fed by several small creeks — Piney Branch, Pinehurst Branch, Broad Branch, Soapstone Branch, and Luzon Branch — and numerous storm sewers.

The Chesapeake and Ohio Canal joins Rock Creek in Georgetown, and used the mouth of Rock Creek as its terminus in Georgetown. At the Tidewater Lock, the creek (and the Canal) empty into the Potomac River. This area, called the "Rock Creek Basin" by the Canal Company, which included a mole, causeway, and waste weir was completed in 1831.[3] Subject to silting up, it was dredged several times for the Canal's use.[4]

The Maryland portion of the watershed comprises the second-largest watershed in Montgomery County, about 60 sq mi (160 km2). About 21 percent of the creek's watershed is in Washington. Total land usage in the watershed is 896 acres (3.63 km2) of wetlands or water, 22,272 acres (90.13 km2) of residential and commercial areas, 15,488 acres (62.68 km2) of forest or grasslands, and 10,304 acres (41.70 km2) of agricultural areas. The creek has a fairly steep gradient, with rapid changes in elevation. The man-made Lake Needwood is located on the creek, north of Rockville.

Water quality and restoration

Rock Creek in Chevy Chase, Maryland. Stream bank shows downcutting (vertical erosion) due to stormwater runoff.

In Maryland, most of the northern Rock Creek watershed has good to excellent water quality, according to studies conducted by the county government. In 2004, to preserve water quality in partially developed areas, the county imposed restrictions on development (i.e., designation of "Special Protection Areas") in parts of this sub-watershed.[5] The southern portion of the Maryland watershed is highly urbanized. Most of this portion of the creek and its tributaries have poor water quality.[6] The county is managing several stream restoration projects throughout the watershed.[7]

The D.C. segment of Rock Creek also has poor water quality. In addition to typical urban stormwater pollution problems such as runoff from streets and other impervious surfaces, the creek has high bacteria levels due to combined sewer overflows (CSOs).[8] The D.C. government, which has a stormwater discharge permit from the United States Environmental Protection Agency, is improving its stormwater management to raise water quality in Rock Creek.[9] In 2009, the District of Columbia Water and Sewer Authority began a planned two-year effort to replace portions of the combined sewer with separate storm sewers, and so eliminate CSO-related problems in the creek.[10]

Fish species observed in Rock Creek and its tributaries include blacknose dace, bluntnose minnow, yellow bullhead, satinfin shiner, swallowtail shiner, longnose dace, and American eel.[11]

Restoration projects

Boulder step pools were installed to raise the water level and allow fish to swim over a partially-submerged sewer pipe which crosses the creek.

In 2006, the National Park Service finished a project to remove or bypass eight fish barriers in the creek by adding a fish ladder to bypass the 1905 Peirce Mill Dam, modifying historic fords, and removing abandoned sewage lines and fords. The effort is designed to restore American shad, river herring, and other migratory fish to the creek and their historic upriver spawning grounds.[12] It is estimated that 2 million fish migrate up the creek each year.

The D.C. government completed a restoration project on the Milkhouse Run and Bingham Run tributaries in 2013. As of 2014, ongoing restoration projects in the watershed include the Broad Branch and Klingle Run tributaries.[13][14]

Tributaries

(Listed in order from the mouth upstream)

In D.C.
In Maryland

See also

References

  1. ↑ U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map, accessed August 15, 2011
  2. ↑ U.S. Geological Survey, Baltimore, MD, 2002. Water Quality, Sediment Quality, and Stream-Channel Classification of Rock Creek, Washington, D.C., 1999-2000. Anita L. Anderson et al. Water-Resources Investigations Report 02-4067.
  3. ↑ Unrau, Harland D. "Historical Resource Study: Chesapeake & Ohio Canal" (PDF). [US Department of the Interior, National Park Service]. Retrieved 2013-05-02. p. 251
  4. ↑ Unrau p. 22
  5. ↑ Montgomery County Department of Environmental Protection (MCDEP). Rockville, MD. Special Protection Area Program Annual Report 2005. January 2007.
  6. ↑ MCDEP. Rock Creek Watershed Restoration Action Plan, July 2001.
  7. ↑ MCDEP. Restoration Projects in the County. 2010-09-14.
  8. ↑ U.S. Environmental Protection Agency. Philadelphia, PA. February 27, 2004. Decision Rationale: Total Maximum Daily Loads for Fecal Coliform Bacteria in Rock Creek.
  9. ↑ District of Columbia. Department of the Environment. August 17, 2007. 2007 Implementation Plan: District of Columbia NPDES Permit No. DC0000221 Municipal Separate Storm Sewer System.
  10. ↑ District of Columbia Water and Sewer Authority (2009). "Rock Creek Sewer Separation - 2009." Fact Sheet.
  11. ↑ National Park Service (NPS), Washington, D.C. (June 2012; rev. June 2015). "National Capital Region Network Resource Brief: Fish, Rock Creek Park."
  12. ↑ NPS. "Removing Barriers to Restore Fish Populations." The Current (newsletter). Vol. 2, No. 3. Fall 2007.
  13. ↑ District of Columbia, Dept. of the Environment. "Habitat Restoration." Accessed 2014-03-29.
  14. ↑ District of Columbia, Dept. of Transportation (2014-01-16). "Klingle Valley Trail Public Meeting."

External links

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