Four Mile Run flows through residential areas as well as urban corridors in south and western Arlington.
Four Mile Run is the largest stream flowing through Arlington, draining approximately two-thirds of the County.
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, about 10 percent of the upper reaches of Four Mile Run were found to be in actively eroding condition, while many areas of the stream were beginning to naturally stabilize or had been artificially stabilized. In the lower reaches, more than 25 percent were in stable condition, about 20 percent were naturally stabilizing and about 6 percent were actively eroding.
About Four Mile Run
A study by the Northern Virginia Regional Commission (NVRC) examined the sources of the bacteria, showing the major sources of identifiable bacteria were urban wildlife (waterfowl and raccoons), humans and dogs. A Total Maximum Daily Load (TMDL) has been created for Four Mile Run, and a management strategy for controlling anthropogenic sources of bacteria to the stream has been created. The NVRC has more information about the Four Mile Run TMDL.
Watershed retrofit studies for Four Mile Run have also been completed.
Macroinvertebrate Monitoring Data
Since 2001, there have been two monitoring sites located on Four Mile Run.
- Bluemont Park, south of Wilson Boulevard.
- Banneker Park, slightly downstream of the Arlington County and City of Falls Church line.
Barcroft Park, located in south Arlington, was added and monitored for a short time in 2005. The site was reinstated in 2009 with new volunteer support.
Macroinvertebrates commonly found are:
- 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.
- Macroinvertebrate data for Four Mile Run Banneker Park
- Macroinvertebrate data for Four Mile Run Barcroft Park
- Macroinvertebrate data for Four Mile Run Bluemont Park
- Fish data for Four Mile Run Banneker Park
- Fish data for Four Mile Run Barcroft Park
- Fish data for Four Mile Run Bluemont Park
Click on one the graphs above for an enlarged version.
Bacteria Monitoring Data
There are 10 sites on Four Mile Run that volunteers monitor for bacteria. Learn more about bacteria monitoring data.
- Blue line: Measured bacteria levels.
- Orange line: Primary contact recreation water quality standard, 235 E. coli CFU/100 mL. Primary contact recreation activities have a high probability for total body immersion or ingestion of water, like swimming, canoeing and kayaking.
- Gray line: Secondary contact recreation water quality standard, 1,173 E. coli CFU/100 mL. Secondary contact recreation activities don’t have a high probability of total body immersion or water ingestion, like skipping rocks or fishing.
- The graphs below can be enlarged by clicking on them.