Hydrographic polygons in and around Fairfax County. The original data in this layer was captured during the 1997 data conversion effort for Fairfax County. After that an update capture was completed in 2014 using stereo models from the 2009 Virginia State imagery. Subsequent to that an update capture was completed in 2022 using stereo models from the 2017 Virginia State imagery. The most recent planimetric update was completed in 2024 using orthoimagery from the 2023 and 2022 Eagleview Orthophotos.

This dataset contains lakes, ponds, streams, rivers, etc. within the established constraints of the dataset development. The data set width threshold for double line stream polygons is > 20' and < 20' for all single line features. The determination of a 20-foot-wide stream is based on the average width over the length of the segment. So, if a stream segment on average is 20 feet or wider then that stream becomes a double line stream and will be a polygon as well as a stream centerline down the middle. Typically, from that point on downstream that stream will be a double line stream.

Contact: Fairfax County Department of Information Technology GIS Division

Data Accessibility: Publicly Available

Update Frequency: As Needed

Last Revision Date: 3/1/2024

Creation Date: 1/1/1997

Feature Dataset Name: GISMGR.PLANIMETRIC

Layer Name: GISMGR.HYDRO_AREAS