1. Introduction
5
1.2.2 Refraction
It was assumed that energy is transmitted only in the direction of wave
propagation under the phenomenon of “shoaling”. However, due to large
variations in the seabed contours, the waves will start bending as the portion
of the wave crest in deeper waters will move faster than the portion of the
same crest in shallower waters. This phenomena defined as wave refraction
is illustrated in Fig. 1.4.
We can consider a point on a wave front in the offshore and traverse this
point towards the shore, which basically represents the wave direction. If we
identify yet another point on the same wave front in the offshore separated
by a distance, bo and trace its movement, it obviously will be separated by
a distance “b”, the relationship between bo and b that could be derived from
the famous Snell’s law will be governing the behaviour of the waves in the
near shore. Equating the power in deep and shallower waters along with the
respective directions of the wave, the relationship between the wave heights
in the offshore and shallow waters can be derived as
H _ 11 Zl\ /Co\ [bo
Ho~ 2\n) \ C ) \ b
(1-2)