COLUMBUS, Ohio - By the time vacationers first dip their toes in beach sand next summer, scientists may have a new weapon in the battle to protect U.S. coastlines from erosion.
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.
With this new method, one video camera with special software does the same work as scientists' only current alternative: an expensive grid of electronic sensors planted beneath the waves.
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.
At a recent meeting of the American Geophysical Union in San Francisco, Lippmann and his colleagues reported that their video-derived data compared 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 envisions the Ohio State camera and software system would eventually cost no more than $100,000 total.
Another plus: 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.
To test their system, Lippmann and Ohio State research associate Jennifer Shore set up a video camera atop a 130-foot tower on the beach in Duck, NC, a popular tourist destination in the Outer Banks region.
Duck is also 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 camera filmed a 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.
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.
The concept of erosion may sound simple -- water washes away sand -- but the movement of the water in the surf zone is anything but simple, he said.
As water crashes against the shore, Lippmann explained, the waves and currents interact with the underwater surface to create complex swirls and eddy currents that defy methods for stalling erosion.
For instance, 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 actually 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 (FEMA). 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. In the spring of 2001, he will conduct these same tests with the camera suspended from a blimp tethered to a Monterey, CA, beach. Partners for that experiment will include the Naval Postgraduate School.
The Office of Naval Research funded this work.
Materials provided by Ohio State University. Note: Content may be edited for style and length.
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