The two systems are complementary. ESI maps provide a nationally standardized, color-coded index of sensitivity of the shoreline to oil spill response. The ESI system uses wave exposure, substrate type, and biological productivity to assign a shoreline ranking (1-10) that reflects the relative degree of sensitivity to oil spills. ShoreZone includes these ESI index ratings and a second index, the Oil Residence Index, used to describe the self-cleaning ability of the coast based on a combination of wave exposure and substrate type (Bartlett & Smith 2001; Harney 2008).
Both ESI and ShoreZone techniques document biological resources, but they do so in distinct yet complementary ways. For example, ESI maps include locations of seal haul-outs and bird colonies, which ShoreZone does not. ShoreZone biological data relates to the presence and relative abundance of supratidal, intertidal, and nearshore flora and fauna such as salt marsh vegetation, eelgrass, algae, and kelps. ShoreZone provides detailed biologic and geomorphologic attributes in a spatial database; downloadable GIS layers; collection and public web-posting of high-resolution aerial imagery; ability to download that imagery; and a query engine to create your own data layers and models.