A Tale of Two Coasts


The coasts are a desirable place to live, a source of jobs, and a valuable resource for recreation.  When we talk about the coast, however, what do we really mean?  There are numerous definitions, even within NOAA, each serving different purposes. I’ll be talking about two definitions used by NOAA. While they don’t address every possible need, they are a good starting place.

The “Coastal Shoreline” Coast

Many times, when people quote statistics about the coast, they are describing people at risk from hazards such as storm surge, sea level rise, bluff erosion, or shallow coastal flooding.  These types of hazards affect the thin swath of land directly along the shore. This coast is defined in terms of the 452 Coastal Shoreline Counties in the United States and its territories.

The “Coastal Watersheds” Coast

While there is the small area directly adjacent to the shores of the US that are most at risk from hazards, there is a larger area that has impacts on our coastal waters. The coastal watersheds have direct impacts on the water quality and environmental health of the bays and nearshore waters. Those impacts can have large economic implications if they negatively affect the habitat for important fishery species, or the quality of the recreational resources that draw people to areas. There are 769 Coastal Watershed Counties (including the US territories).

Map showing the difference between coastal shoreline counties and coastal watershed counties

That’s great, but now what?

So, you know these definitions.  Now what, you say? With two very different definitions, it’s important to know when to use one or the other of them. If you’re thinking about populations at risk from coastal hazards can say with confidence that 39% of the US population live within the Coastal Shoreline Counties–the area most at risk from coastal hazards.

Donut charts showing the U.S. population in coastal shoreline counties (39%) and coastal watershed counties (52%)
Source: National Coastal Population Report – Population Trends from 1970-2010

On the other hand, maybe you’re thinking about green infrastructure as a tool to manage water quality. In this case, you’d use the full suite of Coastal Watershed Counties, because constructed wetlands in the upper watershed can have an effect on the water quality in nearshore areas.

These two coastal definitions won’t suit every need, but they meet a lot of them. In addition, they serve as good examples of the importance of choosing the right geography for your analysis. And remember, it’s mighty easy to lie with statistics, even unintentionally, so make sure you are upfront and clear about what you are using when citing your numbers!

Gabe Sataloff

I am a reformed database administrator who now works in the Human Dimensions program doing GIS work with data about people. While I work with data about people, I'm not normally allowed to talk TO people since I am a former database administrator. I started with my GIS work at a small college in the hinterlands of upstate New York before deciding to move to the warmer climate of South Carolina, getting a Masters of Environmental Science at the College of Charleston as a consequence. The College of Knowledge is where I really got my GIS chops, working on things from mapping bobcats on a barrier island to creating an interactive campus map. I was lucky enough to get an internship at the NOAA Office for Coastal Management straight out of grad school, and thus began the circuitous path from spatial analyst to general tech geek to database administrator to spatial analyst. Now I spend my days clicking buttons and looking at maps about things like ocean economics and social vulnerability.

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