Difficult Run is a 15.9 miles (25.6 km) tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

 of the Potomac River

Potomac River

The Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately long, with a drainage area of about 14,700 square miles...

 in northern

Northern Virginia

Northern Virginia consists of several counties and independent cities in the Commonwealth of Virginia, in a widespread region generally radiating southerly and westward from Washington, D.C...

 Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The term "run" for "stream" is common usage in this part of Virginia and throughout the mid-Atlantic

Mid-Atlantic States

The Mid-Atlantic states, also called middle Atlantic states or simply the mid Atlantic, form a region of the United States generally located between New England and the South...

 region; another "run" is better known in American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 history: Bull Run

Bull Run (Occoquan River)

Bull Run is a free-flowing tributary stream of the Potomac River that originates from a spring in the Bull Run Mountains in Loudoun County, Virginia, and flows south to the Occoquan River...

. Difficult Run flows through Fairfax County

Fairfax County, Virginia

Fairfax County is a county in Virginia, in the United States. Per the 2010 Census, the population of the county is 1,081,726, making it the most populous jurisdiction in the Commonwealth of Virginia, with 13.5% of Virginia's population...

 to Great Falls Park

Great Falls Park

Great Falls Park is a small National Park Service site in Virginia, United States. Situated on 800 acres along the banks of the Potomac River in northern Fairfax County, the park is a disconnected but integral part of the George Washington Memorial Parkway...

, on the Virginia side of the Potomac River. The portion of the run through the park has been characterized as "a miniature Mather Gorge

Mather Gorge

Mather Gorge is a river gorge south and just downriver of Great Falls on the border of Maryland and Virginia. The Maryland side of the gorge is Bear Island, part of the Chesapeake and Ohio Canal National Historical Park, and the Virginia side is part of Great Falls Park. Both parks are National...

 and Great Falls

Great Falls of the Potomac River

The Great Falls of the Potomac River are located at the fall line of the Potomac River, upstream from Washington, D.C. Great Falls Park, operated by the National Park Service, is located on the southern banks in Virginia, while Chesapeake and Ohio Canal parkland is located along the northern banks...

." In the Great Falls area the run is relatively flat and wide at the top of the trail with calm waters, like the Potomac River above Great Falls. The stream picks up speed as it narrows into a steep gorge with waterfalls and quickly reaches the same level as the Potomac. At the mouth of Difficult Run, one can see a panoramic view of the Potomac River.

Watershed

The Difficult Run watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 is the largest in Fairfax County at 37179 acres (150.5 km²). The following subwatersheds make up the Difficult Run Watershed:

• Captain Hickory Run
• Piney Run
• Colvin Run
• Snakeden Branch
• Little Difficult Run
• Rocky Run
• Angelico Branch
• Piney Branch
• Wolftrap Creek
• Rocky Branch
• Lower Difficult Run
• Sharpers Run
• Middle Difficult Run
• Upper Difficult Run
• South Fork Run
• The Glade
• Old Courthouse Spring Branch
• Dog Run

Parks and trails

Using community planning, a secluded 12 miles (19.3 km) hiking and biking trail was built along Difficult Run from Reston

Reston, Virginia

Reston is a census-designated place in Fairfax County, Virginia, United States, within the Washington, D.C. metropolitan area. The population was 58,404, at the 2010 Census and 56,407 at the 2000 census...

 to Great Falls Park. The trail is well-known among area mountain biking enthusiasts for its rolling terrain which makes for fast, smooth rides although there are portions requiring technical skills. The portion of the trail that sees the most mountain biking activity starts near the end of Michael Faraday Court, behind SkateQuest-Reston ice skating rink and follows the tributary stream valley to Lake Fairfax. From Lake Fairfax the trail crosses over Hunter Mill Road and follows Difficult Run itself all the way to Great Falls Park. Great Falls Park is a unit of the George Washington Memorial Parkway

George Washington Memorial Parkway

The George Washington Memorial Parkway, known to local motorists simply as the "G.W. Parkway", is a parkway maintained by the U.S. National Park Service. It is located mostly in Northern Virginia, although a short section northwest of the Arlington Memorial Bridge passes over Columbia Island,...

, and is administered by the National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

. In addition, almost the entire length of Difficult Run is paralleled by the Cross County Trail, which is maintained by the Fairfax County Park Authority for continuous coverage along the run.