Methods for classifying shorelines include review of existing maps, literature, and remote imagery, incorporated with observations from low-altitude aerial surveys and ground observations.
Base maps, shoreline, wetland boundaries, and aerial photographs are gathered prior to a survey. Using this information, along with any previous studies of the area, the geologist completes a preliminary shoreline classification. This classification is modified during the fieldwork process.
Fieldwork consists of two parts: aerial surveys and ground verifications. During the overflight phase, the geologist annotates the shoreline base map with ESI Rankings, carefully noting transitions in habitats. Shorelines with more than one ESI type in the intertidal zone are annotated on the map in order from landward to seaward ESI classification. A segment of coastline may be assigned up to three ESI shoreline types. In areas where the coastline has changed significantly from the base map (either through natural or artificial processes), the geologist modifies the base map by hand. In addition to classifying the shoreline, the observer takes representative low-altitude, oblique photographs for each ESI habitat.
Ground verification consists of spot-checking to confirm aerial observations. Ideally, an example of each habitat is visited and photographed from the ground. At a minimum, ground verification concentrates on confirming grain-size classification for sedimentary substrates, since this can be difficult to recognize from the air. If a portion of the coast is identified during the overflights as problematic or difficult to classify, that segment is ground checked and maps are updated according to the ground observations.
Once the field component of the project is complete, the maps are scanned and the digital shoreline arcs are updated with the ESI attributes noted in the field. The shape and position of the digital shoreline may also be modified at this time to reflect field observations. After the information from the field map has been incorporated into the digital database, the ESI shoreline is color-coded and replotted at the same scale as the original base maps. The geologist then compares the classified shoreline plots to the original field-annotated base maps and any errors in shoreline attributes, as recorded in the GIS database, are corrected.
SENSITIVE BIOLOGICAL RESOURCES - ESI maps depict oil-sensitive animals and rare plants, as well as habitats that are used by oil-sensitive species. Some habitats, such as submersed aquatic vegetation and coral reefs, that are themselves sensitive to oil spills may also be depicted.
Biological resource information is gathered from local officials who provide expert knowledge and suggest relevant source materials for biological resources in the study area. When the data have been collected and reviewed, the biologist plans how each resource will be mapped throughout the entire study area. During this process, it may be necessary to prioritize the species to be mapped in order to avoid excess clutter, which makes the final product difficult to read or interpret. Considerations may include species that are rare or listed as protected or endangered, or those species that have a particular commercial, recreational, or cultural value in the area. It may also be appropriate to limit some species-mapping to particularly critical life stages, such as nesting or spawning. Biological features are mapped as points, polygons, and lines, and are given unique numbers corresponding to associated data tables, for easy identification and editing.
HUMAN-USE RESOURCES - ESI maps also include human-use areas that could be impacted by an oil spill, or that could provide access for spill response operations. They include areas that have added sensitivity and value because of their use, such as beaches, parks, and marine sanctuaries; water intakes; and archaeological sites. Human-use resources are divided into four major components: high-use recreational and shoreline access locations, management areas, resource extraction locations, and archaeological and historical cultural resource locations. Each human-use resource is assigned a feature type and feature code. Management areas are typically mapped as polygons, while the remaining socioeconomic resources are generally depicted as points.
For more information about the data sources and process for a particular resource, refer to the metadata record for the desired resource in the ESI atlas of interest.
Animals, plants, and habitats potentially at risk from oil spills are segmented into seven elements based on major taxonomic and functional groupings. Each element is further divided into groups of species or sub-elements with similar taxonomy, morphology, life history, and/or behavior relative to oil spill vulnerability and sensitivity. Attribute data include: species names (common and scientific), the legal status of each species (state and/or federal threatened, endangered, and special concern listings), concentration/abundance, seasonal presence by month, and special life-history time-periods (e.g., spawning, nesting).
Human-use resources can be subdivided into four major components: high-use recreational and shoreline access locations, management areas, resource extraction locations, and archaeological and historical cultural resource locations. Each of these elements is further subdivided based upon types of use.