Little Pimmit Run


Almost 90 percent of Pimmit Run is located outside Arlington. Included within this area is the Little Pimmit Run watershed, of which 57 percent is located within Arlington. The portion of Little Pimmit Run within the County’s border is located in north Arlington in a primarily residential neighborhood. 

Drainage Area

Little Pimmit Run drains into Pimmit Run, then the Potomac River. Pimmit Run has a drainage area of 12.4 square miles. While the Little Pimmit Run subwatershed includes Arlington and Fairfax counties, our legal authority is only limited to runoff generated within Arlington’s borders. 

Little Pummit Run Samping Site Map
Drainage area for the Little Pimmit Run monitoring site.

Rapid Stream Assessment Technique Scale: Fair

In 2011, we assessed all the streams in the County as part of the Stormwater Master Plan Update. The assessment used the Channel Evolution Model to evaluate which sections of the streams are actively eroding to prioritize them for stream restoration. During that assessment, Pimmit Run was evaluated to be a priority stream for stream restoration given that approximately more than 30 percent of the stream length assessed was found to be in an actively eroding state. In addition, less than 3 percent of the stream channel has been artificially stabilized. Although 70 percent of Little Pimmit Run was found to be in an actively eroding state, almost 90 percent of the stream has been artificially stabilized. 

About Little Pimmit Run

In 2008 and 2009, a watershed retrofit study of Little Pimmit Run was completed. 

Macroinvertebrate Monitoring Data

Little Pimmit Run Stream Monitors

The monitoring site is located near the intersection of 38th Street North and North Dumbarton Street. Volunteers began monitoring this site in January 2002.

Macroinvertebrates commonly found are:

  • Aquatic worms
  • Amphipods
  • Black flies
  • Flatworms
  • Midges
  • Net-spinning caddisflies
  • Small minnow mayflies

In fall 2011 and spring 2012, we contracted a professional monitoring group to collect family/genus-level macroinvertebrate and fish data at each of our volunteer monitoring sites.

Little Pimmit Run Macro Graph.jpeg(JPEG, 206KB)
Click on the graph above for an enlarged version.

Bacteria Monitoring Data

There is one bacteria monitoring site on Little Pimmit Run located near the intersection of 38th Street North and North Dumbarton Street. Learn more about bacteria monitoring data.