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Technology Solutions Attacking beach erosion coasts. In the United States alone, one-fourth of coastal structures are threatened by erosion that will occur over the next 60 years, according to a federal study released last summer. When erosion allows rare formations like barrier islands to slip away, it can have environmental consequences. The sand displaced by erosion may affect coral reefs by increasing turbidity. And some of the remedies for beach erosion, such as “nourishUSGS
The hidden forces that suck beaches into the surf are growing less murky thanks to a cadre of researchers patrolling the sands in specially equipped dune buggies, jet skis, and small planes. In time, the U.S. Army Corps of Engineers hopes that this research will enhance their arsenal of antierosion weaponry. The pristine-looking stretch of sand outside the Field Research Facility in Duck, NC, operated by the
PeterRuggiero ofthe W ashington State DepartmentofEcologycollected nearshore bathymetric data forthe Southw estW ashington CoastalErosion Studyusing a speciallyequipped jetski.
Army Corps of Engineers is the beststudied beach in the world, according to William Birkemeier, chief of the 24-year-old facility. That reputation, teamed with the Duck site’s ability to represent many U.S. coastal locations, lures researchers from around the world to test new equipment there. The techniques being developed at the site “are changing the way we look at beaches,” Birkemeier says. Although much of beach erosion is natural, it can be accelerated by anthropogenic forces. Whatever the cause, it is a serious problem because people throughout the world persist in building along scenic sea144 A
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ment”, also known as supplementation, can also cause at least shortterm environmental problems. The majority of the action, in terms of the sand movement, that can lead to erosion, takes place where the waves break on the sand, Birkemeier says. Because of its highly dynamic nature, that zone is one of the most difficult places for researchers to take measurements, he explains. “For much of near-shore science’s history, we’ve had very few data points in the breaking zone,” he says, adding that the Army Corps of Engineers has an interest in sand movement because of its mission to maintain navigable waterways.
ENVIRONMENTAL SCIENCE & TECHNOLOGY / APRIL 1, 2001
The Field Research Facility earned its premier position in near-shore science with its invention of the Coastal Research Amphibious Buggy (CRAB), a 35-ft-tall submersible wheeled tripod that began gathering Duck beach data in 1978. It has been joined by a wide variety of tools and techniques since then. In the past few years, a new generation of equipment has emerged, thanks to recent advances in computer imaging technology and global positioning systems (GPS), and new insights about how to couple some relatively inexpensive technologies with beach-accessible vehicles. Slowly but surely, these tools are revealing a three-dimensional picture of how the surf moves the sand, Birkemeier says. The most surprising observations, Birkemeier says, have resulted from studies made with the souped-up dune buggy dubbed Surveying Wide Area Shorelines (SWASH), devised by Jeff List of the U.S. Geological Survey (USGS). By prowling up and down the shoreline at low tides before and after a storm, List learned that areas of the Outer Banks beaches recovered almost all of the sand that had been washed away by an October storm within 5 days, far more quickly than anyone expected. The SWASH buggy’s three-dimensional data come from a special GPS with four antennas that is capable of tracking beach position down to the cubic centimeter. Although other ocean researchers use dune buggies, the SWASH is the only one able to record three-dimensional data, Birkemeier says. Its ability to enter shallow water and its relatively low $60,000 price tag both enhance its appeal, he adds. What the SWASH cannot capture is where the sand goes, Birkemeier says. This is where the jet skis come in. Reggie Beach, a researcher at Oregon State University, found a way to conduct complete hydrographic surveys using jet skis equipped with GPSs and echo sounders to deter© 2001 American Chemical Society
mine the depth of the seafloor beneath them. Guy Gelfenbaum, an oceanographer with the USGS’s coastal and marine geology program, has been using the jet skis to map out underwater geography along the coasts of Oregon, Washington, and North Carolina since 1998. The North Carolina tests showed that the jet skis can collect data similar to that accumulated by the CRAB device. The advantages of using the jet skis are their greater portability and lower price ($40,000–$50,000), Gelfenbaum says, noting that he transports them via a flat-bed truck to wherever he wants to gather data. He adds that they can take measurements in places on the West Coast that are otherwise inaccessible to boats and humans. An important complement to the local-scale data collected by SWASH and the jet skis is the regional data that Tom Lippmann, a research scientist in Ohio State University’s Civil and Environmental Engineering and Geodetic Science Department, is collecting by taking aerial video images from a small Cessna 172 plane with a GPS system. It took Lippman a year
The SW ASH dune buggyhascollected some surprising data on itsrunsup and dow n the shore ofNorth Carolina’sOuterBanks.
to assemble his collection device, which fits into a standard Cessna airplane door and costs $50,000. The concept of aerially surveying the shoreline is not new, but Lippmann’s technology can reveal the presence of sandbars, unlike technology that costs upward of $1 million. Lippmann has been flying over the coastlines of North Carolina, southern California, Oregon, and Washington since 1997, and the data that he is gathering allow observers
to follow changes over time. Because all of that data is computerized, researchers can compare the information they are gathering at the local scale with what is happening at the regional scale, he says. If List drives up and down the North Carolina coast before and after a storm, the data that Lippmann compiles by flying over can show how the position of offshore sandbars affects the shoreline erosion that List has measured, Lippmann explains. “Lippmann’s work is important because it shows what is going on in sandbars,” Birkemeier says. And Birkemeier and Lippmann agree that the links this research is illuminating between sandbars and beach erosion may prove to be very important in helping policy makers to pinpoint areas where erosion is likely to be a problem. Although researchers cannot piece together the whole story of beach erosion, it is an exciting time in the field of near-shore science, Birkemeier says. In the next few years, it is likely that the turbulent science will grow increasingly more exact. KELLYN S. BETTS
APRIL 1, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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