Defining Coastal Lands for Conservation in a Changing Climate

There are various definitions of “coastal lands” that are used on this site.

Conservation in a Changing Climate includes references to the National Climate Assessment or NOAA data when applicable, which typically means either states that contain coastal watersheds or coastal counties. These definitions typically include the Great Lakes. You can view regional impacts and resources for more detailed information.

NOAA’s Definitions

NOAA tends to describe coastal lands as “Coastal Shoreline Counties,” which are “counties that have a coastline bordering the open ocean, or contain FEMA identified coastal high hazard areas in the SFHA” or “Coastal Watershed Counties” which means either (1) at a minimum, 15 percent of the county’s total land area is located within a coastal watershed; or (2) a portion of a county, or an entire county, accounts for at least 15 percent of a coastal USGS 8-digit cataloging unit. Using these definitions, there are 452 Coastal Shoreline Counties and 769 Coastal Watershed Counties in the United States.

Source: National Climate Assessment: Coasts map depicting population change in “watershed counties”.


According to the U.S. Census Bureau, coastal counties have experienced population growth and density increases between 1960 to 2008.

In 2012 NOAA reported that nearly 40% of the U.S. population lived in “Shoreline Counties”.

Coastal Data
Source: NOAA’s State of the Coast.

NOAA reports that from 1960 to 2015, the population density in all coastal counties (excluding those in Alaska) will have grown from 187 to 327 persons per sq mi. This is about three times the national average. These trends indicate that growth of coastal counties will continue, especially in warmer climates such as the Southeast, Gulf of Mexico, and Pacific regions.

Coastal Lands and the National Climate Assessment

Unless indicated otherwise, the National Climate Assessment describes “Coastal Watershed Counties” when discussing impacts to coastal populations.