More MetadataMaintenance and Update Frequency: Floodplain boundaries are updated by Building and Development staff as detailed floodplain studies are submitted and floodplain alterations are approved and structures are built in association with land development applications.Abstract: The regulatory floodplain boundary reflects the limits of flooding resulting from a storm having an occurrence probability of 1% in any given year, identified as the 100-year storm. The floodplain boundary was was revised on February 17, 2017 for consistency with FEMA’s National Floodplain Hazard.Purpose: Floodplain data are used to establish a Floodplain Overlay District (FOD) as defined in the Zoning Ordinance of Loudoun County, which restricts the allowable uses within the regulatory floodplain. Data are used to establish flood risk factors and eligibility to participate in the National Flood Insurance Program. Floodplain data are also used in land use planning and for taxation of land.Note: Users should beware of the dynamic nature of floodplains and floodplain mapping when using this data. Our floodplain boundaries are based on the best available information, but are still approximate in many areas where detailed studies have not been conducted.Completeness Report: Floodplain data is incomplete countywide due to unavailability of data within Town and Dulles International Airport limits. Features may have been eliminated or generalized due to scale and intended use. To assist Loudoun County, Virginia in the maintenance of the data, please provide any information concerning discovered errors, omissions, or other discrepancies found in the data.Flood Plains:Major Flood Plain = Drain Area > 640 AcresMinor Flood Plain = Drain Area > 100 Acres and < or = 640 AcresApp. Num: The associated Loudoun County Application NumberData Owner: Department of Building and Development