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Land
development through urbanization plays a significant role in
changing the hydrologic balance in our watersheds. Impervious
surfaces such as rooftops, asphalt roads, and concrete replace
the trees, shrubs, groundcover, and soil that retain and filter
stormwater. The net outcome of increased imperviousness is a
significant increase in surface runoff.
Streams, the main recipients of increased
runoff, make room in the channel by eroding the banks and bed.
The result is a wider and deeper channel. As the stream erodes
vertically and laterally, sediment and attached nutrients wash
downstream. Even in a healthy, stable stream, some erosion
and deposition can occur during major storm events. However,
when runoff in a watershed increases dramatically, erosion and
deposition become excessive.
NVSWCD promotes the physical rehabilitation
of streams through restoration or stabilization techniques.
Watershed planning in advance of development can prevent stream
problems. However, in the absence of appropriate and consistent
planning, streams are likely to degrade. In Fairfax County,
many streams have suffered as a result of upstream development.
The District works with County, state, and federal agencies
and homeowner associations to identify streams with economically
feasible rehabilitation potential. Once streams are identified,
the District collaborates with these agencies to do the restoration
or stabilization work. The District provides project coordination,
grant writing and support, technical advice, and publicity for
the projects.
Examples projects that the District has participated
in include the Kingstowne
Stream Restoration Project (1999) and restoration of
Snakeden Branch
in Reston (2003).
To learn more about how to address stream
erosion problems, contact
NVSWCD's urban conservation engineer or call 703-324-1427.
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