Fairfax County Land Use February 2014

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Fairfax County Land Use February 2014

Watershed Management Plans

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Fairfax County Land Use February 2014

  1. 1. Watershed Management Plans A Fairfax County, Virginia Publication, February 2014
  2. 2.  Develop countywide land use/land cover GIS data layers useful for plan development ◦ Watershed characterization (i.e. maps, data analysis) ◦ Pollution and hydrologic modeling  Key requirements ◦ A layer containing a land use mix for existing and future conditions  Key parameter for modeling water quality ◦ A layer containing impervious values (connected and disconnected) for both conditions  Key parameter for modeling water quantity
  3. 3.  Tax Administration Dept. real estate records ◦ Each record contained a unique code for each parcel  Existing land use Codes > 200 types  Zoned land use  Adopted land use comprehensive plan ◦ Polygons containing planned land use information ◦ Twenty-two planned land use categories  Parcel data ◦ Polygons contained a unique ID for each parcel ◦ Included vacant and underutilized parcels  Planimetric data (1997 aerial photography)
  4. 4.  The need to simplify (i.e. group) land use types through consolidation was evident ◦ 200 codes (included embedded towns) ◦ Code numbering convention facilitated consolidation
  5. 5.   Grouped existing, zoned and planned land use types into 11 categories Miscellaneous:  OS - Open Space  GC - Golf Course  INT - Institutional:  Government/Universities  IND - Industrial  Airports  Railways Transportation:  TRANS - Road rights-of-way
  6. 6. Existing conditions  Each real estate record was assigned a category for existing, zoned and planned land use  Joined the tabular tax record data to the parcel layer polygons  Included category: TRANS landuse ◦ Areas outside of the parcel boundaries = ROW  Included category: WATER land cover ◦ Planimetric data of the stream network, lakes
  7. 7. Future conditions  Intersected comprehensive plan coverage with the parcel layer ◦ Most parcels were already built-out  Vacant and underutilized parcels ◦ Compared zoned vs. planned land use ◦ Where different, chose classification that yielded the greatest density
  8. 8. Existing conditions - Tysons Corner
  9. 9. Future conditions - Tysons Corner future
  10. 10.  Used planimetric data ◦ Features were assigned a corresponding percent imperviousness  Buildings, roads, parking lots and sidewalks/trails – 100 percent  Parking lots, unpaved – 50 percent  Areas outside planimetric features – 0 percent  Feature types sampled to estimate the typical DCIA/NDCIA split ◦ Roads, parking lots – 100 percent DCIA ◦ Sidewalks/trails – 85 percent DCIA, 15 percent NDCIA ◦ Buildings – DCIA varied by type  Commercial – 100 percent  Industrial – 95 percent  Multi-Family Residential – 90 percent  Single Family Residential – 50 percent
  11. 11. Planimetrics - Tysons Corner
  12. 12.  Estimating existing and future condition imperviousness values by land use ◦ Sampled planimetric data in areas representative for each land use category ◦ Average percent imperviousness was calculated for each land use category ◦ Assigned percent DCIA/NDCIA to each category based on appropriate feature types  DCIA and NDCIA values were aggregated to a “sub-basin” level ◦ Polygons were created for modeling purposes ◦ Typically 300 to 500 acres in size ◦ More than 1800 polygons
  13. 13. Existing percent imperviousness by land use - Tysons Corner
  14. 14. Future percent Imperviousness by land use - Tysons Corner
  15. 15.   The LU/LC methodology Fairfax County implemented for its watershed planning effort worked well at the local scale and could be a method used to help standardize urbanized LU/LC categories across the bay watershed. Many smaller jurisdictions have less readily available data. However, many larger urban areas maintain data similar to Fairfax (i.e. comprehensive plan, tax/parcel information and planimetrics) which could be used with this methodology.
  16. 16. Questions? For more information or to request this document in an alternate format call 703-324-5500, TTY 711 or email SWPDmail@fairfaxcounty.gov Fairfax County Department of Public Works and Environmental Services Stormwater Planning Division 12000 Government Center Parkway Fairfax, VA 22035 www.fairfaxcounty.gov/dpwes/stormrwater Thank you.

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