MATT MARINER BROZE wrote: > Somewhere (possibly the last edition of Waves and Beaches by Willard > Bascom--out of print but a great read for coastal kayakers) I read about a > jetty (maybe in CA) that was destroyed in relatively mild swell because of the > (rare--maybe from the southern ocean) direction the relatively mild swell was > coming from interacted with the underwater topography offshore to focus the > energy from a wide area of sea onto a part of the jetty that was torn apart by > huge waves that were confined to only in a small area. Yup. That's in both versions. I've got the 1984 revision, which details this on pp 82-85. The jetty affected was near Long Beach, CA, and was hit in 1930. Its tip was damaged by waves not sensed anywhere nearby. The focused waves moved large racks running to 4 to 20 tons. These originated from somewhere in the Indian Ocean, and with a period in the 20-30 sec range, were monsters. The feature which focused the waves was a hump in the ocean floor about 10 miles offshore spanning a depth range of 180 to 600 feet. The focusing concentrated a roughly 8-mile long wave front at the outward extent of the hump into an impact zone about a quarter mile wide. At depth, the waves were less than two feet high; they formed breakers about 12-25 feet high when they broke on the jetty. Walter Munk, one of the first oceanographers at Scripps Institute of Oceanography in La Jolla, details studies using wave-sensing arrays scattered about the Pacific which did the detective work tracing wave trains similar to the ones that did that damage to a source about 13,000 miles distant from the California shoreline. There is a great interview of Munk in the December 2009 issue of The Surfer's Journal, a popular journal on surfing, often stepping afield from shots of surf stars on mega waves. Munk and his family spent several months on a remote SE Pacific island, monitoring the nearby array, as guests of the local chieftain. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Wed Jan 27 2010 - 14:28:42 PST
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