Section A 



MM — WW 



Section 



+ 5.50(1896)- 



El. +4.80 

 +4.20(1.933) 



+ 2.80 



Figure 59. 



Cross sections of seawall, Yamada, Japan (from Iwasaki and 

 Horikawa, 1960). Dimensions in meters. 



Caution is also necessary when placing seawalls in a harbor area. 

 A seawall may cause waves to reflect into the harbor. It was determined 

 at Hilo, Hawaii, that a seawall might aggravate surge conditions within 

 the harbor (U.S. Army Engineer District, Honolulu, 1960). 



In some instances, trees may offer some protection against a tsunami 

 surge. Groves of trees alone or as supplements to shore protection struc- 

 tures may dissipate tsunami energy and reduce surge heights. Groves of 

 coconut palms (Fig. 60) may withstand a tsunami surge but may be sheared 

 off by debris carried forward by the tsunami. Other types of trees may 

 be easily uprooted and flattened. Figure 61 shows a grove of pandanus 



165 



