Rincon Island, Punta Gorda, California, is an offshore island manmade in 1958. It was the first such island to be built with an ocean exposure. The island, located in a depth of about 45 feet, is composed of armor rock and tetrapod revetments enclosing a sand core. A pile-supported causeway about 2,700 feet long connects the island to the shore. Major findings of an evaluation of the island's performance in the more than 14 years of its existence show: that the revetment has not been damaged by wave attack; that subsidence ranging from about 3 inches to 1.5 feet has occurred, mainly due to the deterioration of some inferior material in the revetment; that littoral transport has been almost unaffected; that adjacent bottom topography shows minor changes; and that a large, thriving community of marine organisms has developed in the environment created by the island. The report includes recommendations for instrumentation to provide measurement of waves and nearby bottom sedimentation. (Author)
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