Adjustment of Bikini Atoll to ocean waves

Atolls in the trade‐wind belt withstand a continuous heavy pounding from ocean waves. Against the windward side of Bikini Atoll alone it is estimated that waves dissipate 500,000 hp, one‐fourth the power generated at Hoover (Boulder) Dam. To withstand these forces the exposed reefs are moulded into a most effective natural breakwater, consisting of long narrow grooves in the seaward face of the reef, and surge channels on the reef flat. These surge channels are tuned to the prevailing wave periods. Their distribution around the reef conforms to the distribution in wave activity, which in turn is controlled by prevailing winds over the North and South Equatorial Pacific. Some of the power of the breaking waves is utilized to maintain a water level just inside the surf zone about 1.5 ft above the general sea level. The water flows downhill over the reef into the lagoon, regardless of the stage of the tide, with an average speed of 0.5 to 1.0 knot, but occasionally with speeds up to four knots. The reef as a biological community utilizes this current and maintains thereby a wave‐resisting and modifying structure.