"A typical example of a location subject to damage "by 

 horizontal currents is Santa Cruz Harbor (shown in Figure 208). 

 During the 196^ tsunami the water level varied from a high of 

 11 feet to a low of about -8 feet MLLW. During the major 

 portion of the drawdown, the water level dropped at a rate of 

 about 1 foot per minute for about 10 to 15 minutes. Obviously, 

 strong horizontal currents were produced by this disturbance. 

 A floating hydraulic dredge was docked near the entrance just 

 before the tsunami arrived. One of the early waves induced 

 such a drag on the dredge that the mooring lines parted and 

 the dredge was swept seaward. As it moved out the entrance, 

 it struck the east jetty and finally sank along the entrance 

 channel on the centerline extension of the east jetty. 

 Shortly thereafter a 38-foot cabin cruiser struck a submerged 

 object (presumably the sunken dredge) while attempting to 

 leave the harbor and sank. The strong currents induced by 

 the tsunami also caused movement of material in the entrance 

 channel bottom. Several small floats located near the public 

 pier were damaged from being caught against the pier and were 

 wrecked or twisted as the water fell. With the exception of 

 damage to the small floats mentioned above, all other floating 

 facilities withstood the tsunami. 



"inside of San Francisco Bay both the May 196O and March 

 196^4 tsunamis were greatly attenuated after passing through 

 the Golden Gate. Based on very limited data, a tsunami at 

 Richmond on the north and Hunter's Point on the south is 

 reduced to one-half the height at the Golden Gate. A tsunami 

 at the easterly end of San Pablo Bay and Alviso on the south 

 is reduced to less than one-tenth the height at the Golden 

 Gate. Damage in San Francisco Bay was largelv to pleasure 

 boats. The highest damage was reported from marinas in 

 Marin County where strong currents caused boats, and in some 

 cases, portions of floating slips to break loose. These ob- 

 jects attained the velocity of the moving water and cauL^d 

 damage when they struck the other craft. 



"At Noyo Harbor the entrance is restricted, but the harbor 

 is also restricted and the full effects of the waves were felt 

 over the entire reach of the harbor. In the March 196U tsunami 

 the first wave rose relatively slowly, and exhibited the 

 characteristics observed elsewhere along the coast. The 

 second wave, occurring about 15 minutes after the first, 

 formed a bore-like face, about 7 feet high, consisting of 

 a series of step-like jiimps. One observer saw the bore form 

 at the entrance and rapidly drove his automobile at about 30 

 miles per hour parallel to the travel of the bore, but was 

 unable to pass it. At Noyo damage was to floats and to 

 commercial fishing vessels that broke loose during the 

 tsunami . " 



326 



