X-SciTech

Making Waves

January 22, 1998 / 6:18 PM EST / AP

Future military commanders planning attacks from the sea will benefit from work being done on the North Carolina coast by a team of 100 scientists and an odd-looking research vehicle called a CRAB.

The data gathered during the Sandy Duck project also could help beach towns set policy on how close to the ocean it is prudent to build and could tell dredge operators how long a channel might stay open.

Sandy Duck, a $15 million, three-year experiment that continues this year, is sponsored by the U.S. Army Corps of Engineers Field Research Facility. The facility has a 1,840-foot concrete pier and unrestricted access to 3,000 feet of prime beach land. Posh beach homes line the shore on either side of the government complex.

"We're interested in the movement of sand, when it comes off the beach, where does it go and how does it change," said Bill Birkemeier, the scientist in charge of the research center. "The more we understand how the system works, how the sand moves, the easier it is to plan and to work with the system.

"It's our Mars landing. Of course, the Mars landscape doesn't change overnight."

In simple terms, the scientists and the CRAB vehicle, which drives into the ocean taking measurements and towing instrument sleds, are studying the way sand flows as breakers hit the beach. The CRAB, or Coastal Research Amphibious Buggy, is powered by a Volkswagen engine and resembles a duck blind perched on a huge moving tripod. The machine, built by Corps personnel for the study, can drive about 3,000 feet into the ocean to a depth of 28 feet.

Measurements are done with fiber optic backscatter sensors, which measure sand grain size, and side-scan sonar that paints pictures of the ocean floor. Acoustic current meters measure currents some distance away and acoustic altimeters measure drops in the ocean floors during erosion.

Scientists from six government agencies and 18 universities are feeding the information into computers and analyzing it.

It is possible to quantify the loss of sand from a beach, but scientists can't yet tell where it goes. Intensive study of the beach here and the sea bottom- in the breaker zone and beyond -could yield clues.

For example, Birkemeier said, time-lapse photos of the sand bar just off the beach show how it changes during storms. The bar, called the near bar, is irregular during calm weather; however, during storms it appears to move offshore and parallels the shore in a near-solid line. The still photos have been put on videotape. When played , they resemble a snake slithering along the shore.

Such studies could have significant military applications, said Thomas Kinder, a program officer from the Office of Naval Research in Arlington, Va.

Understanding what happens at Duck could give a commander clues to what's happening off a beach elsewhere in the world and aid the decision of where to send a rubber boat full of commandos or a laning craft loaded with relief supplies.

"Knowledge of the environment - the battle space - is important for naval and Marine Corps operations, like weather for aviators," Kinder said. "What we want to do is eliminate some of the risk in the decision making. Our intention is to be able to understand the environment of a lot of these beaches and advise naval commanders."

During D-Day invasions of France in World War II, Kinder said, landing craft might have dropped troops in ankle-deep water instead of waves over their heads if there had been a better understanding of the ocean bottom.

Gen. Dwight Eisenhower's "decision would have been less risky and the routing of some ships might have been different," Kinder said. "Fewer amphibious tanks might have sunk."

Carl T. Friedrichs, a researcher from the Virginia Institute of Marine Science, is studying why and how sand moves between the outer surf zone and the inner edge of the continental shelf, but no farther.

"In other words, what keeps beach sand from being washed out into depths of 40 feet or more during winter storms and never returning," Friedrichs said.

"This is an important economic issue because millions of dollars are spent on beach renourishment in the U.S. each year. Understanding whether or not sand is likely to be washed out onto the shelf will help predict whether such large expenditures make sense," he said.