Condition of the Watershed
The Little Hunting Creek Watershed was developed during a time when stormwater was treated by piping it off roads and yards and into the nearest stream as quickly as possible. For decades, Little Hunting Creek and its tributaries have functioned as giant storm sewers, and were damaged as a result.
About 92% of the watershed is developed, and 25% is covered by impervious surfaces, such as parking lots, roads, driveways, and roofs. During rain storms, such surfaces produce large volumes of runoff at high velocity that damage streams. To halt and reverse the damage, both the amount and velocity of stormwater runoff must be reduced.
Assessments conducted by Fairfax County and the Commonwealth of Virginia over the past 30 years find streams in the Little Hunting Creek Watershed in poor condition because of:
Streambank erosion and sedimentation
Stormwater runoff has resulted in an actively widening stream bed and unstable banks in the upper reaches of Little Hunting Creek and its tributaries.
Head cuts (highly eroded stream banks--see picture at right) are created by high volumes and velocities of stormwater runoff.
Sediment is carried downstream, and about 50% to 60% of the bottom of streams in the watershed is affected by sediment deposits.
Riparian (streamside) buffer loss
Over half the stream buffers in the watershed are deficient because they are too narrow or lack vegetation and are paved or covered with lawn.
Poor water quality
The water is nutrient-enriched--that is, it contains too much nitrogen and phosphorus--and aquatic life is threatened by excessive algae in the tidal waters of Little Hunting Creek.
Measures of fecal coliform are high.
Dissolved oxygen in the North Branch is low--at the minimum level needed to support aquatic life.
Fish taken from the creek have high levels of polychlorinated biphenyls (PCBs) in their tissues, leading the Virginia Department of Health to issue a health advisory for fish consumed from the creek.
Chlordane has been found in sediment samples from the tidal portion of Little Hunting Creek, above the level that threatens aquatic life.
Low biological health
Stream habitat quality is rated as poor or very poor for 73% of the length of streams in the watershed, and fair for 27%. None of the streams have any portion rated as good or excellent.
Macroinvertebrate assessment ranking is very poor. Diversity is low and only pollution-tolerant species live in the streams of the watershed.
Number of fish species in upstream sampling sites is moderate.
Sources
For more information about the condition of the watershed, see
Chapter 2 of The Little Hunting Creek Watershed Management Plan.
Fairfax County Stream Water Quality Report. Annual.