Tracing the Coastline

Before you can know what coastline is lost to hurricanes and sea level rise, you need to know what land is there. Researchers have finished the most complete mapping of the NC coast including oceanside, bayside, and all of the estuaries. Now they can track what happens next.

OUTER BANKS — Stand on the beach on the Outer Banks. Feel the ocean breeze. Sink your toes in the sand as the surf washes in and then out. It’s relaxing. It’s peaceful. But what you probably don’t realize is that you are witnessing North Carolina’s coastline changing.

That’s because with each wave that breaks and washes ashore as well as with every gust of wind, the coast is altered.

Sometimes the change is dramatic, as when a hurricane or a nor’easter washes out Highway 12 on Hatteras Island. But more often, the change is too small to be seen right away and it only becomes clear over time. The only constant is that North Carolina’s coast is dynamic and it is ever changing.

“If we want to evaluate the changes along the coast you have to start with a baseline,” explains Dr. Reide Corbett, a professor at East Carolina University and University of North Carolina Coastal Studies Institute. “You have to know what your coast is before you can look at how things are changing on different time scales, such as a decade or multiple decades or even just after a storm.”

But while North Carolina’s coastline was known, there had never been a serious effort to precisely document the coast, especially as a way to document how the coastline changes over time.

Building on nearly a century's worth of data — from late 1800s captain’s maps to modern day aerial and satellite images — researchers from East Carolina University created the North Carolina Coastal Atlas. It’s an online tool — the digital definition of the state’s coastline — not only showing where the land meets the water but also depicting what type of coast it is.

“We documented everything,” says Corbett, who explains why the effort took several years. “We wanted to show if that portion of the coast was a sandy beach, a marsh, a swamp forest, or if it was modified and if that modification was a building or a dock.”

The survey discovered some interesting facts.

North Carolina boasts roughly 322 miles of ocean shoreline. But if you step away from the oceanfront, the survey also found the state has the second largest estuarine system in the United States. There’s almost 12,009 miles of estuarine coastline. Combined, that gives North Carolina 12,331 miles of coastal shoreline.

The estuarine coastline includes bays, sounds and wetlands. Researchers found the state’s coastal shoreline is dominated by wetlands. Marshes make up the largest type of wetlands, but the survey found there are also swamp forests and sediment banks, such as river deltas and the banks of streams.

Perhaps most important, the North Carolina Coastal Atlas also shows how the coast is changing and what is driving the change. Surprisingly, for all of the development along the combined coastline, only about 600 miles, or 5%, of the coastline has been modified.

Corbett was surprised, but also pleased, by just how little of the entire coastline has been modified. But he says it’s a good example of why the North Carolina Coastal Atlas will be a valuable tool for local governments, planners and developers. In trying to understand how the changes along the coast will affect developments and where people will move now and into the future, a baseline of what the coast looks like is needed.

“We talk about shoreline change, sea level rise and storm inundation, but it all depends on where the shoreline is, what the shoreline is and how the shoreline is moving,” says Corbett. “And as the shoreline retreats over time, even a slight change will influence homes and property owners behind the shoreline."

Corbett believes understanding the changes will make for better property owners and developments.

The North Carolina Coastal Atlas focused not only on how the state’s shoreline is changing but also what is influencing the change, including storms and the gradual erosion and movement of the shore.

Besides the changing oceanfront, with which everyone is familiar, researchers also focused on the loss of wetlands. That’s because marshes and swamp forests are vital for storm protection as well as protecting the water supply and providing food and shelter for wildlife.

Besides setting a baseline for tracking how the coast is changing, the creation of the North Carolina Coastal Atlas also sounds a warning. Researchers found that 92% of the coastal shoreline, both ocean and estuarine, is eroding. It is often happening at the same time but at different rates.

“We have to focus on the changing coast because we are seeing the impact of erosion and sea level rise all around us,” says Todd Miller, Executive Director of the North Carolina Coastal Federation. “We’re already having houses fall in the ocean because of our changing coastline and we have to be careful about building sea walls because those walls could harm some of the most valuable estuaries and fisheries in the world.”

The atlas will be updated to reflect changes caused by new construction, erosion from storms, and even sea level rise. Braxton Davis, Director of the North Carolina Division of Coastal Management, which helped with the project, believes the atlas will not only show how the coast is changing but also answer basic management questions.

“Just being able to answer the basic questions, such as how many docks we have, helps us to understand not only the state of the system and how trends are moving, but also helps with all sorts of daily management questions,” explains Davis. “The more information we have gives us a better understanding of the coast we are all watching change over time so we can come up with the right management solutions.”

“Generally speaking, if something has been changing for the last 30 years, we expect it will continue to change in the future and most likely it will change more rapidly,” says Corbett, who reminds everyone that the coast is a dynamic system. “And while sections of the coast follow a pattern of growth and erosion, over the long term the coastline is eroding.”

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