State of the Streams 2024

Little Falls Branch

Little Falls Branch is a small tributary of the Potomac, stretching only 3.8mi in length. Despite its small size, Little Falls has a long history of serving both Montgomery County and Washington DC. The branch was formerly called Powder Mill Branch, named after the Longborough Mill that operated alongside the stream. Up until 1864, it used to serve as a drinking water source for Washington, D.C.​

Report Highlights and Opportunities for Improvement:

Little Falls Branch stood out from the other streams in the report in its wetlands scores. Historically, Little Falls Branch has been a highly urbanized stream with approximately 20% of its length still channelized with concrete. In the 15-year period over which we measured wetland loss, maintenance or gain, Little Falls was the only stream that gained wetlands in its watershed. This is incredibly important to improving the health of the stream. While Little Falls Branch scored a perfect fish passage score due to not having any dams, waterfalls or road passages, this score does not reflect the impact that channelization has on fish populations that are not able to live upstream due to the barriers that this channelization creates.

Little Falls Branch had the greatest opportunity for improvement in its riparian buffer score. The stream scored 0 in this factor with only 33% of the stream being surrounded by 100’ thick riparian buffer. Riparian buffers not only provide vital habitat for wildlife, but they also help to protect streams from climate impacts, such as heat and stormwater runoff.  Little Falls runs through a highly urbanized community that impairs its riparian buffer.It has been altered by underground pipes, open concrete channels and culverts.

With a poor riparian buffer and a highly urbanized surrounding community, you can see the effects on Little Falls through its benthic macroinvertebrate or BIBI score, which reflected a poor stream environment for benthic macroinvertebrates to thrive.

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Little Falls Branch

INDICATORSSCORES
Impervious Surface53
Fish Populations (FIBI)75
Benthic Macroinveterbrates (BIBI)23
Water Chemistry94
WATER QUALITY – TOTAL61
INDICATORSSCORES
Fish Passage100
Stream Habitat80
Invasive Plants62
Birds95
BIODIVERSITY – TOTAL84
INDICATORSSCORES
Tree Canopy57
Air Quality86
Stream (Riparian) Buffer0
Wetlands100
CLIMATE – TOTAL56
INDICATORSSCORES
Tree Canopy85
Park Access95
ACCESS – TOTAL90
LITTLE FALLS BRANCH / GRAND TOTAL74 – FAIR