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.