Land Development Services

CONTACT INFORMATION: Monday through Thursday, 8 a.m. - 4 p.m. and Friday, 9:15 a.m. - 4 p.m. Please note that visitors may not be added to in-person queues past 3:45 p.m.
703-222-0801 TTY 711
12055 Government Center Pkwy
Fairfax, VA 22035
Bill Hicks

Development in Dam Break Inundation Zones

Any proposed development that will occur in the dam break inundation zone of a state-regulated impoundment that has been mapped and is on file with the County must be identified on all Preliminary Plats, Subdivision Plans, Site Plans and Minor Site Plans. A dam break inundation zone is the area downstream of an impoundment that would be flooded by failure of the impoundment’s dam.

As part of the plan review process, the county will notify dam owners and the Virginia Department of Conservation and Recreation (DCR) of any proposed development in the dam break inundation zone of a state-regulated impoundment. DCR is required to determine the potential impacts of the proposed development on the spillway design of the dam and notify the dam owner and the county of its determination. If the proposed development will require changes to the dam’s spillway, the development cannot be approved unless it is modified to avoid changes to the spillway or the developer pays half the cost of the necessary upgrades. In addition, when any part of a proposed subdivision is in a mapped dam break inundation zone, this fact must be noted on the Final Subdivision Plat for the development.

The requirements only apply to proposed developments downstream of a state-regulated impoundment for which a dam break inundation zone map is on file with the county at the time of the official submission of a plan to the county. The requirements for proposed developments located in dam break inundation zones and construction of state-regulated impoundments are contained in the Subdivision Ordinance, the Site Plan Provisions of the Zoning Ordinance and Chapter 6 of the Public Facilities Manual.

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