Vegetation types in the study area were initially identified using information obtained from previous vegetation mapping efforts in the Carnegie SVRA (HDR 2004, Jones and Stokes 2000, DPR 1980) and the Existing Vegetation(Eveg) maps (USFS 2007) for the study area. Eveg maps were created by the United State Forest Service (USFS) using automated, systematic procedures, remote sensing classification, photo editing and field based observations to efficiently and cost-effectively map large areas with minimal bias. The classification is a provisional system that meets the floristically based level of the National Vegetation Classification Standard hierarchy. Eveg vegetation cover maps are produced at relatively low spatial detail (1:24,000 map scale) to provide a broad overview of existing vegetation in California.The vegetation types were then refined through aerial photograph interpretation using aerial imagery provided to AECOM by DPR (2010) and National Agricultural Imagery Program (NAIP 2009) aerial imagery to identify areas where vegetation cover may have changed since the previous mapping efforts were completed, or where vegetation boundaries may not have been drawn accurately due to the methodology, classification system, or mapping scale used. AECOM botanists mapped vegetation type polygons in a GIS overlay from aerial photograph interpretation during September and October 2011. Vegetation types were mapped at a fine-scale (1:6,000 map scale) in accordance with the Memorandum of Understanding for Cooperative Vegetation and Habitat Mapping and Classification mapping standards (California Biodiversity Council 2002). The minimum mapping unit is 1 acre for all common vegetation types. All discernible sensitive habitats, including wetland and riparian vegetation types and linear aquatic features (e.g., streams, rivers, ditches) were mapped regardless of size. For woodland vegetation types, trees on the edge of the polygon were included when they were within approximately two average tree canopy widths of the polygon (approximately 30 meters).AECOM then conducted a field verification survey of the study area on December 7 and 8, 2011, to verify, refine, and correct the vegetation types mapped in the office. The vegetation cover and linear aquatic feature GIS data layers created during the prefield mapping exercises were printed on 1 inch = 500 feet scale maps and also loaded onto a Trimble Global Positioning System (GPS) device with the 2010 DPR aerial imagery and compared for consistency with conditions observed on the ground. Areas that deviated from vegetation types mapped from aerial photography were corrected and refined in the field on the hard copy maps and digitally using the GPS device. The boundaries of wetlands and drainages were further refined using data from the wetland delineation conducted in the study area in 2010 (DPR 2010). Representative photographs were taken of each vegetation type.
