Wave propagation through Apra Harbor entrance and diffraction in the

harbor occurs simultaneously with local wave generation inside the harbor.

Significant wave height at the dock resulting from these two components can be

estimated by assuming that the total energy density in the sea surface is equal to

the sum of the energy densities due to each wave component. Since energy

density is proportional to wave height, this gives:

(19)

where

harbor entrance

Waves also partially reflect from the dock. Interaction between incident and

reflected waves effectively increases significant wave height adjacent to the

dock by a factor of one plus the reflection coefficient. Assuming waves are

symmetric about the swl, one-half of the significant wave height will rise above

the swl. Finally, the elevation reached by the crest of the significant wave

incident to the dock can be calculated as

(20)

where

swl = still-water level due to tide and storm effects

Reflection coefficient values used in this study are 0.5 along the exposed dock

face with southwest exposure and 0.1 along the relatively protected dock face

with exposure to the south.

These relationships are included in the Fortran program HARBOR so that a

time-history of *WL*s can be easily calculated for each typhoon modeled.

Storm damage reduction programs and design of coastal structures typically

require a storm-surge analysis to obtain a peak water-surface elevation for design

water levels. Because typhoons and hurricanes occur infrequently at a given site,

abundant storm-surge stages are generally not available and standard ranking

27

Chapter 3

Modeling Approach

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