Watershed Management Program
The Technical Review Committee, comprised of engineers and planners from the public works and environmental services departments of local governments, is responsible for the technical investigations required to determine the flooding/SWM impacts of future land use changes and drainage modifications. Technical and administrative support for the program is provided by NVRC staff.
The Watershed Management Program relies upon the Four Mile Run Computer Model to simulate the watershed's complex hydrology and to forecast interjurisdictional impacts of stormwater runoff from local land use changes and drainage modifications. Cumulative impacts are reviewed on a quarterly basis, and corrective measures are recommended if the model projects flooding problems.
NVRC staff uses the watershed model to develop projections of peak stream flows and water surface (flood) elevations at critical control points in the watershed and recommends ways in which adverse impacts can be eliminated or mitigated. The potential for a proposed land use change or drainage modification to cause flooding in the Arlandria area can be analyzed simply by the following methodology: 1) Revise the computer model's land use database or channel configuration to represent the proposed project and 2) examine the model's output. The computer model also is used to evaluate the effectiveness of various proposed stormwater detention facilities for which downstream effects would not otherwise be known. Finally, the model has been employed to help analyze a number of "what if" scenarios related to stream flow and flooding at various user-specified locations throughout the watershed.
To date, the computer-based watershed model has analyzed over 650 local land use changes affecting stream flow, which cumulatively represent the addition of over 200 acres of impervious ground cover. Reflected with these land use changes in the model are 110 runoff control structures that collectively hold a total of over 32 acre-feet of detention storage. Additionally, the construction of Route I-66 through the watershed resulted in the conversion of 100 acres from open space to impervious cover as well as the addition of 47 acre-feet of detention storage to the watershed, both of which are represented by the Four Mile Run computer model.
Congress and the USACE view the Four Mile Run Watershed Management Program as an important prototype for future watershed management elsewhere in the United States. NVRC views the program as an excellent example of how jurisdictions can collaborate to develop regional solutions to water resources problems which spill over jurisdictional boundaries. In short, the watershed management program constitutes a regional planning effort that continues to function effectively, and one in which all of its participants can take great pride.