Frequencies of Crest Heights for Random Combinations of Astronomical Tides and Tsunamis Recorded at Crescent City, California.

Of particular concern to the U.S. Army Corps of Engineers is the protection of Crescent City, California from future tsunami damage. Six tsunamis having maximum wave heights greater than one foot have hit Crescent City since 1946 4 see Fig. 1. The last two occurred on May 23, 1960 and March 28, 1964. Their wave heights were 10.5 ft and 22-26 ft, respectively, and the tsunamis caused millions of dollars of damage. Presently studies are being conducted by the Corps to evaluate the required height of a seawall fronting the ocean. The report presents a method for taking into account the random occurrence of tsunamis with respect to the astronomical tide. The important parameter describing the tsunamis damage potential is assumed to be the maximum total water level during the occurrence of a tsunami. The total water level is assumed to be the sum of the tide water level and the tsunami water level with respect to the tide. The method is applied to the 1960 and 1964 tsunamis that were recorded on the Crescent City tide gage at Duttons Dock. The result is a histogram of the maximum total water level for each of the tsunamis which can then be used to evaluate the severity of the tsunamis. Author