Surf Videos Could Help Fight Erosion

COLUMBUS, Ohio, January 2, 2001 (ENS) - Researchers at Ohio State University have developed a new way to map the ocean currents that erode beaches, cost coastal towns millions of dollars in annual property losses, and threaten a tourist industry worth billions of dollars.

With this new method, one video camera with special software does the same work as the current system - an expensive grid of electronic sensors planted beneath the waves.

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Observation tower in Duck, North Carolina. The Ohio State University camera, seen on the right side of the ledge, is pointed at the beach's surf zone where ocean waves break and circulate against the shore. (Photos courtesy Thomas Lippmann)
The new software uses foam from breaking waves to track the complex flow of water near the shore, explained Thomas Lippmann, research scientist in Ohio State's Department of Civil and Environmental Engineering and the Byrd Polar Research Center. The Office of Naval Research funded this work.

At the fall meeting of the American Geophysical Union in San Francisco, Lippmann and his colleagues reported that their video derived data compares favorably to data obtained by the in-water instrumentation.

"If we could better measure and predict water circulation patterns, we could learn more about erosion, as well as other near shore phenomena such as rip currents and undertow," Lippmann said, referring to the fast moving currents often responsible for swimming accidents on beaches.

Lippmann explained that the sensors scientists now use to study waves and currents make individual measurements at single locations, whereas water circulation patterns tend to vary over much larger areas. Scientists must install dozens of sensors to study a single section of beach, and placing the sensors correctly is difficult and expensive.

The sensors cost anywhere between $5,000 and 20,000 each, and installation doubles the cost. So an array of 30 sensors could cost as much as $1.2 million - an amount beyond the reach of all but a few research programs worldwide, Lippmann said.

He predicts that the Ohio State camera and software system would eventually cost no more than $100,000 for the equipment plus installation.

The video camera could be moved from place to place with relative ease, so the same system could travel around the country and study many beaches.

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Duck Beach in North Carolina is the scene of the Ohio State University erosion experiments.
To test their system, Lippmann and Ohio State research associate Jennifer Shore set up a video camera on a 130 foot tower on the beach in Duck, North Carolina, a popular tourist destination in the Outer Banks region. Duck is a popular spot for researchers investigating ocean waves, so Lippmann and Shore were able to take advantage of the fact that researchers from several other institutions including the Scripps Institution of Oceanography had previously installed an array of sensors called current meters under the water along the beach.

The Ohio State video camera filmed a 1,625 foot (500 meter) stretch of the beach's surf zone, the area where ocean waves break and circulate against the shore. The new software analyzed the image of the water, focusing on the white, foamy patches of bubbles left after breaking waves passed. Based on where the foam moved, the software calculated the speed and direction of the currents.

Lippmann said that data from the video based measurements matched data taken by the current meters to within 10 percent.

Erosion is a process that is more complex than it seems. With the Ohio State camera system, scientists may soon have a tool to help them better understand erosion and how to manage it, Lippmann said.

Residents along the coastal U.S. have tried to counter erosion by adding sand to beaches or building artificial seawalls out of wood or rocks, but some recent studies have shown that these efforts may increase erosion in certain situations.

Storms, rising ocean levels, and beachfront development all contribute to the problem, according to a recent report by the Federal Emergency management Agency. The agency estimated that erosion along U.S. coastlines could cause $500 million in annual losses if current population and erosion trends continue.

As erosion eats away at a shoreline, it brings homes and businesses closer to the water, making buildings more vulnerable to flooding and storm damage. Over the next 60 years, erosion may claim one out of every four houses within 500 feet of the Atlantic, Gulf Coast, Pacific and Great Lakes shorelines, the report stated.

Lippmann believes the Ohio State software and camera system would work even better if it could film from directly above the water. This spring, he will conduct these same tests with the camera suspended from a blimp tethered to a Monterey, California beach. Partners for that experiment will include the Naval Postgraduate School.