National Geographic : 1962 Dec
KODACHROMESBY JAMESR. ROOT (ABOVE) AND B. ANTHONYSTEWART© N.G.S. Artificial Beaches Help Engineers Guard Shores To study wave action, the U. S. Army Corps of Engi neers uses a series of tanks at its Beach Erosion Test Grounds, Washington, D. C. Earthmovers first build a beach in a 635-foot, 112 million-gallon tank (left). Then six-foot waves are sent crashing onto the sands (below). To create these breakers, the bulkhead at far end slaps the water every 6.5 seconds. Jet-type vacuum cleaner in the hands of Sherry Myers, Jr., sucks up drifted sand that waves have borne from hopper at upper right to trough in foreground. By weighing the sand, techni cians determine the amount moved by waves. Green dye and stopwatch enable Robert P. Stafford to measure speed of water movement. The men work in a tank resem bling a giant wading pool.