Figure 61. Grove of pandanus trees knocked down by 



1946 tsunami on the Island of Kauai, Hawaii 

 (from Shepard, MacDonald, and Cox, 1950). 



trees which were knocked over in parallel rows by the 1946 tsunami in 

 Hawaii (Shephard, MacDonald, and Cox, 1950). Reid and Taber (1919) noted 

 that palm trees were uprooted by the 1918 Puerto Rico tsunami. Shepard, 

 MacDonald, and Cox (1950) indicated that dense thickets of hau trees pro- 

 vided effective shields in many places during the 1946 tsunami in Hawaii. 



Matuo (1934) calculated that trees could be broken by water velocities 

 of 2 meters per second or greater, but did not analyze specific types of 

 trees. He indicated that trees broken off by higher velocities may add 

 debris to the surge and increase the damages resulting from the surge. 

 Magoon (1965) indicates that a buildup of debris in front of a structure 

 may increase its effective area. This would result in an increased drag 

 force, and may cause the entire structure to be swept away by the tsunami. 



3. Other Shoreline Structures. 



Damage from a tsunami may occur to structures located at the shore- 

 line or along river channels near the shoreline. In 1964, a dock at 

 Crescent City, California (Fig. 62), was damaged when the water elevation 

 increased to 2 meters above the deck elevation, uplifting a large lumber 

 barge moored to the dock (Wilson and Tjzfrum, 1968). The tsunami surge at 

 Seaside, Oregon, destroyed a bridge over the Necanicum River and a rail- 

 road trestle over Neawanna Creek. Shepard, MacDonald, and Cox (1950) 



167 



