Black-and-white aerial photography at a scale of 1:24,000 was the principal source of information used to assess distribution and abundance of SAV in Chesapeake Bay, its tributaries, and the Delmarva Peninsula coastal bays from Assawoman Bay to Magothy Bay in 2011. There were 160 flight lines that yielded aerial photography negatives that were scanned and orthorectified to create orthophoto mosaics. These mosaics were carefully examined on-screen and outlines were drawn to identify all SAV beds visible on the photography, providing a geographic information system (GIS) digital database for analysis of bed areas and locations.Ground survey information collected in 2011 was tabulated and entered into the VIMS SAV GIS digital database.

However, while the entire Bay was flown, some portions of the Bay were not mapped since SAV signatures were masked by excess turbidity present months after the passage of Hurricane Irene and Tropical Storm Lee. The regions that were not mapped are contained within nine CBP segments, including the Middle, Upper and Western Branch of the Patuxent River; the Middle and Upper Potomac River; Piscataway Creek; and the Anacostia River.

The aerial photography is carefully examined to identify all visible SAV beds. Photographs covering SAV beds are scanned and orthorectified to create orthophoto mosaics. Outlines of SAV beds are then interpreted on-screen, providing a digital database for analysis of bed areas and locations. Ground survey information collected in 2011 is tabulated and entered into the SAV geographic information system (GIS). SAV distribution data are presented and discussed based on the 2003 revised Chesapeake Bay Program (CBP) segmentation and zonation scheme (DAWG, 1997). This segmentation scheme is mapped, listed by salinity regime, and delineated descriptively.

The CBP Segmentation scheme defines 93 segments that are grouped into three zones for this report. The Upper Bay Zone includes the Susquehanna River and extends to the Chesapeake Bay Bridge; the Middle Bay Zone extends to the southern boundaries of CB5MH, TANMH, and POCMH; the Lower Bay Zone extends to the mouth of Chesapeake Bay and includes the James River. The salinity within each zone roughly coincides with the major salinity zones of estuaries: polyhaline Lower Zone (18-25 ppt), mesohaline Middle Zone (5-18 ppt); oligohaline Upper Zone (0.5-5 ppt). Although the major rivers and smaller tributaries of Chesapeake Bay have their own salinity regimes, each river is included within the zone where it connects to the Bay.

SAV distribution in the Delmarva Peninsula coastal bays is presented and discussed separately from Chesapeake Bay. A fourth zone, the Delmarva Peninsula Coastal Bays Zone, is defined to include the region from Assawoman Bay to Magothy Bay and is subdivided into five segments: Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and Southern Virginia coastal bays.