Complete Chain

The intertidal habitats of Prince William Sound and the Copper River Delta were mapped during overflights conducted by an experienced coastal geologist during 14-19 May 1999. The shoreline classifications were denoted onto 1:63,360 U.S. Geological Survey (USGS) topographic maps. The shoreline classifications were then transferred onto maps on which the shorelines derived from both National Wetlands Inventory (NWI) data and USGS Digital Line Graph (DLG) were plotted. The DLG shoreline was used in most cases; the NWI shoreline and polygons for tidal flats and marshes were used when they best represented the current shoreline conditions, especially in the Copper River Delta and other areas of extensive flats and marshes. Prediction of the behavior and persistence of oil on intertidal habitats is based on an understanding of the dynamics of the coastal environments, not just the substrate type and grain size. The sensitivity of a particular intertidal habitat is an integration of the following factors: 1) Shoreline type (substrate, grain size, tidal elevation, origin); 2) Exposure to wave and tidal energy; 3) Biological productivity and sensitivity; 4) Ease of cleanup. All of these factors are used to determine the relative sensitivity of intertidal habitats. Key to the sensitivity ranking is an understanding of the relationships between: physical processes; substrate; shoreline type; product type; fate and effect; and sediment transport patterns. The intensity of energy expended upon a shoreline by wave action, tidal currents, and river currents directly affects the persistence of stranded oil. The need for shoreline cleanup activities is determined, in part, by the slowness of natural processes in removal of oil stranded on the shoreline. These concepts have been used in the development of the ESI, which ranks shoreline environments as to their relative sensitivity to oil spills, potential biological injury, and ease of cleanup. Generally speaking, areas exposed to high levels of physical energy, such as wave action and tidal currents, and low biological activity rank low on the scale, whereas sheltered areas with associated high biological activity have the highest ranking. A comprehensive shoreline habitat ranking system has been developed for the entire United States. The shoreline habitats delineated in Prince William Sound and the Copper River Delta are listed below in order of increasing sensitivity to spilled oil: 1A) Exposed Rocky Shores; 1B) Exposed, solid man-made materials; 2A) Exposed Wave-Cut Platforms in Bedrock, Mud, or Clay; 3A) Fine- to Medium-Grained Sand Beaches; 4) Coarse-Grained Sand Beaches; 5) Mixed Sand and Gravel Beaches; 6A) Gravel Beaches; 6B) Riprap; 7) Exposed Tidal Flats; 8A) Sheltered Rocky Shores and Sheltered Scarps in Bedrock, Mud or Clay; 8B) Sheltered, Solid Man-Made Structures; 8C) Sheltered Riprap; 8D) Vegetated, Steeply-Sloping Bluffs; 9A) Sheltered Tidal Flats; 10A) Salt- and Brackish-Water Marshes. In many cases, the shorelines are also ranked with multiple codes, such as 6A/7. The first number is the most landward shoreline type (6A=gravel beach), with exposed tidal flats (7) being the shoreline type closest to the water. | Description Source: Research Planning, Inc.

Type of geographical feature | Description Source: Research Planning, Inc.

Data source for the ESI | Description Source: Research Planning, Inc.

Regional environment | Description Source: Research Planning, Inc.