VI. TSUNAMI -SHORELINE INTERACTION 



In addition to the shoaling of waves on the nearshore slope, a tsunami 

 may interact with a shoreline in a number of different ways, including 

 standing wave resonance at the shoreline, the generation of edge waves by 

 the impulse of the incident waves, the trapping of reflected incident 

 waves by refraction, and, as the reflected wave from the shoreline propa- 

 gates seaward, the reflection of wave energy from an abrupt change in 

 water depth at the seaward edge of a shelf. Also, a wave arriving at an 

 oblique angle to the shoreline may produce a Mach-stem along the shoreline. 

 All of the above interactions depend on wave reflection at the shoreline. 

 Tsunamis entering inlets and harbors may also produce resonant conditions 

 within the inlets and harbors. LeBlond and Mysak (1977) provide a general 

 discussion of edge waves and wave trapping. 



1 . Wave Reflection . 



The reflection of an incident wave ray from a shoreline is illustrated 

 in Figure 30. The angle, a 1 , between the wave ray and a line normal to 

 a tangent to the shoreline will have the same value for the incident and 

 the reflected wave rays. For a steep nearshore slope, the reflected 

 wave will be in phase with the incident wave. 



Shoreline 



Reflected Wove Ray 



Line Normal to Tangent 



Line Tangent to 

 Shoreline 



Incident Wove Ray 



Wove Crest 



Figure 30. Wave reflection from a shoreline. 



