Monitoring High Hazard Dams, Fairfax County, VA


      high water monitoring station
High water monitoring station


In the past, residents of Fairfax County, Virginia had very little warning concerning water level changes of the high hazard PL-566 dams located throughout the county. To remedy this, officials designed an ALERT flood warning system to monitor water levels at each of the earthen dams, report rainfall totals throughout the watershed, and notify emergency personnel of the possibility of flooding or dangerous conditions.

In March of 2008, HSE was awarded a contract to supply, install and maintain the system. A total of nine packaged water level monitoring stations equipped with rain gauges and one repeater station were installed. The systems' remote water level sensors and rain gauges report by VHF radio to the County's base station computer, which runs DEC DataWise software.

In addition to regular timed reports, the rain gauges report each millimeter of rainfall to the base station. The water level sensors report any change in level based on a user selectable setting as small as 0.01 inch. Fairfax County has set alarm criteria in their software for the new gauges including rainfall levels, water levels, and the rate of water level rise at the dams. When alarm conditions are met, the software can send notification to appropriate personnel via text message and e-mail. The software also retrieves data from the NESDIS database for U.S. Geological Survey gages for display and archiving in the same database as the County's ALERT system.

water level sensor conduit
Water Level Sensor Conduit


      Water Level Station Standpipe at Hampton Forest
Water Level Station Standpipe at Hampton Forest


Water Level Station Standpipe at Hunter Mill
Water Level Station Standpipe at Hunter Mill



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