Environmental Sensitivity Index: How Shoreline Types are Determined

Environmental Sensitivity Index (ESI) maps—products of NOAA’s Office of Response and Restoration (OR&R)—served as the foundational data sets for the State of the Coast “shoreline type” indicator. Though primarily used by oil spill responders to identify which coastal resources are at risk if an oil spill occurs, ESI maps have other potential applications. For example, ESI maps implement a standardized method for classifying coastal geomorphology (i.e., shoreline type). Knowing what type of shoreline is available can help coastal managers and planners determine how shoreline should be managed generally—not just during oil spills—to ensure benefits for the economy, the environment, and coastal communities.  

Working with colleagues in the public and private sectors, OR&R researchers classified most of the U.S. shoreline using a combination of overflight information, aerial photography, ground truthing, local habitat maps, and National Wetlands Inventory data. The source of shorelines on ESI maps varies by state, but, typically, the 1:24,000 shoreline from the United States Geological Survey (USGS) 7.5-minute quadrangle maps is used. For more detailed information, see state-specific metadata.

The “shoreline type” indicator developed for State of the Coast presents a simplified summary of ESI shoreline types by state. To produce these state summaries, ESI shoreline classes were grouped into five general categories as listed in Table 1.

As with many national-scale data sets, ESI maps contain data gaps and peculiarities that users should be aware of. For the purposes of State of the Coast, some states were not included in the “shoreline type” indicator due to lack of ESI data (e.g., Great Lakes states), and some states, though incomplete, were deemed to have sufficient coverage to be included in the indicator (e.g., Louisiana in Figure 1). Also, as ESI maps are primarily used in oil spill response, ESI shorelines often include estuarine and upstream areas where oil might be expected to travel under tidal influence (e.g., St. Johns River, Florida in Figure 2; Columbia River, Oregon/Washingon in Figure 3).

Table 1                             Figure 1                       Figure 2                         Figure 3
ESI Categories   Louisiana Incomplete Shoreline   Inland extent of ESI shoreline along the St. Johns River, Florida   Inland extent of ESI shoreline along the Columbia River, Oregon and Washington
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ESI Categories

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Example of Environmental Sensitivity Index Map. Credit: NOAA