purpose:
This dataset was produced to facilitate regional planning, conservation, and enhancement of biological resources by state
agencies, project partners and regional stakeholders. This vegetation dataset combines mapping in the western Sacramento Valley
with maps produced previously of the Department of Water Resources Central Valley Flood Protection Program's System-wide Planning
Area (floodplains along the Sacramento and San Joaquin Rivers and major tribuataries) and ot the eastern Sacramento Valley.
It is mapped to the Alliance level of the state and national vegetation hierarchy, with exceptions. The DWR mapping area includes
the main-stem rivers and major tributaries (including ancillary natural and semi-natural vegetation) as follows: 1) Within
the Department of Water Resources Central Valley Flood Protection Program's System-wide Planning Area (SPA); 2) Outside of
the SPA but along streams from the King's River north to the town of Red Bluff. This area was determined by buffering the
National Hydrologic Dataset stream centerlines based on mean annual stream flow as follows: >12,500-45,000 cfs, 1.25 miles;
>7,500-12,500 cfs, 1 mile; >3,000-7,500 cfs 0.75 mile; >1,000-3000 cfs, 0.5 mile; and >50-1,000 cfs, 0.25 mile. 3) North of
the USDA Great Valley Ecological Section (GVE) along the main-stem of the Sacramento River to Keswick Dam. The eastern Sacrameno
Valley mapping was funded by the Strategic Growth Council and includes areas within portions of Butte, Yuba, Sutter, Placer
and Sacramento Counties within the GVE but outside the DWR mapping area as described above. The western Sacramento Valley
mapping was funded by the California Department of Fish and Wildlife and Wildlife Conservation Board and includes portions
of Tehama, Glenn, Colusa, Yolo, Solano and Contra Costa counties within the GVE but outside the DWR mapping area as described
above. Mapping was completed from interpretation of the National Agricultural Inventory Program's 2009 (NAIP 2009) aerial
imagery. Polygons were hand-digitized at a scale of 1:2000, with a minimum mapping unit (mmu) of 1.0-acre, and a minimum average
width of 10-meters per polygon. Along with vegetation alliance (or in some cases group or macrogoup in the NVCS hierarchy
when alliance could not be determined from photointerpretation), vegetation cover was estimated for tree, shrub and herb cover.
All of the vegetation cover groups were estimated using "birds-eye total cover," i.e., what can be seen on the aerial image,
excluding understory layers when covered by an over-story layer. The combined DWR and SGC mapping area was assessed for accuracy
by VegCAMP. Overall users accuracy of the map was 88% and producers was 87%, thus exceeding the Federal Geographic Data Committees
standard for such maps of 80%. Accuracy of the western Sacramento Valley portion of the map was not conducted but is assumed
to be similar to the rest of the map given the same classification, imagery, and photointerpreters were used. More information
on the classification can be found https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=64011. More information on the mapping
procedures and standards and the accuracy assessment methods and results can be found here: https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=74420.