The Wetlands of Tysons Last Forest

By definition, wetlands are lands that have wet and spongy soil.  The wetlands of Tysons Last Forest provide the transition between dry land and the stream.  Because of their relationship to the Old Courthouse Spring Branch stream, wetlands serve as a vital link between the land and the water.

The United States Fish and Wildlife Service lists Old Courthouse Spring Branch Stream Valley Park (“Tysons Last Forest”) as classified WETLANDS.


According to the National Wetlands Inventory, Tysons Last Forest is classified with code PFO1A.

P         System PALUSTRINE: The Palustrine System includes all nontidal wetlands dominated by trees, shrubs, emergents, mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean derived salts is below 0.5 ppt.

FO       Class FORESTED: Characterized by woody vegetation that is 6 m tall or taller.

1          Subclass Broad-Leaved Deciduous: Woody angiosperms (trees or shrubs) with relatively wide, flat leaves that are shed during the cold or dry season.

A         WATER REGIME Temporary Flooded: Surface water is present for brief periods during growing season, but the water table usually lies well below the soil surface for most of the growing season.

Why are Wetlands Important?

With their unique natural characteristics, wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs.  Wetlands play an integral role in the ecology of the watershed:

  • Protect and improve water quality:  Filter out sedimentation, decompose vegetative matter and convert pollutants into usable form,
  • Erosion Control:  Counter erosive forces of moving water,
  • Flood Protection: Prevent flooding by holding water much like a sponge, and
  • Animal Habitat: Provide homes for fish and wildlife.
What do Wetlands Look Like? 

Neighborhood Coalition members have taken some amazing photographs of the trees, shrubs, and other vegetation in Tysons Last Forest.  If you look closely, you can see the working relationship between the wetlands and the watershed.

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