The kelp persistence database was developed as part of a GIS analysis to determine the optimal site to build a 150 acre artificial reef as mitigation for kelp losses ascribed to the San Onofre Nuclear Generating Station. The database was constructing by overlaying each of the annual kelp canopy maps produced from aerial surveys conducted by Dr. Wheeler North of CalTech. The aerial surveys extended from Newport Harbor to the Mexican Border and covered the time period from 1967 to 1999. Over 650 survey maps were scanned, georeferenced, classified for kelp canopy area, and composited to produce the final persistence database. The database can be queried in a number of ways to show characteristics such as the total number of years that kelp was present in an area or to show the kelp canopy during any individual year during the survey. The resolution of the final vector database was set at a minimum polygon size of 50 m2, which provided adequate spatial detail and a sufficiently fast redraw time.
The above figure shows the kelp bed offshore of LaJolla, CA. The red areas show the most persistent core areas of this bed where kelp was present during 10 or more years of the 33 years covered by the surveys. These core areas are found at water depths ranging from 35 to 55 feet.