I 



Section VIII. CONCLUSIONS 

 Introduction 



From the details in this study on the origin and effects of the 

 Uaskan tsunami, we now draw conclusions to add to existing knowledge, 

 and provide criteria for the planning and design of protective measures 

 against potential damage. 



In the area affected "by the Alaskan earthquake there was usually 

 a complex interaction between different categories of damage, involving 

 regional earth movement, seismic shock, compaction settlement, slides 

 and fissuring, fire, and tsunami wave damage with associated impact from 

 floating debris. In most cases where major wave damage was involved, it 

 :o\ild be fairly well identified. 



Because this study was started almost two years after the earth- 

 quake occurred, there were few damage cases remaining that could possibly 

 be analyzed for evaluating the wave forces. However, it is possible to 

 arrive at some general conclusions regarding the ability of different 

 structures withstand tsunami forces. 



2. Water Particle Velocities and Pressure Forces from Tsunamis 



It would appear that the damaging effect of tsunamis depends very 

 greatly upon the amplitude and the period of the waves , the nature of the 

 terrain they invade, and the development of breaking or bore formation in 

 the coastal inundation. The availability of easily floatable debris, 

 ■logs, boats, automobiles, and timber-frame structures) which acquire the 

 nomentum of the water, provides a ready means of increasing the damaging 

 punch of the waves when striking obstacles. 



To calculate the force of the water on any obstacle it is necessary 

 to know the velocity and direction of flow, as well as the water level 

 as a function of time. The nature and shape of the obstacle are, of 

 course, of basic importance. 



In tsunami-damaged areas, we have found few cases from which some 

 idea of water particle velocities may be obtained. One case is the over- 

 turning of a locomotive at Seward. Calculations related to the overtiirned 

 engine (see Figure 152) give a water velocity of 2U.5 feet" /second with an 

 average pressure force of TOO pounds per square foot. The approximations 

 made for this calculation are, admittedly rather rough. Using a formula 

 based upon pure frontal drag is open to question, since the direction of 

 water flow around the locomotive may have been oblique rather than normal. 

 The use of the alternative formula (Equation (D-2U) of Appendix D) might 

 also be questionable. It is nevertheless of interest to determine the 

 applicable value of the coefficient K in Equation (D-IT) of Appendix D, 

 that would have yielded the overturning conditions of the locomotive. 



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