COASTLINES Coastlines are the interface between water and land. Waves in water will affect the land in many ways, especially along coastlines. Let's look briefly at why we get waves. Waves on the surface of the water are from wind energy transferred to water due to the friction between the water and blowing air. Water moves in waves that have crests or peaks and troughs or lows. The distance between a crest or trough is called the wavelength, while the height of the wave or wave height is from the crest down to the trough. The wave amplitude is not the same as the wave height. It is defined as half the wave height and is measured from the middle point to the crest. The wave period is the time it takes to get one crest to pass and another to arrive at any given point. The wave speed or velocity is the forward momentum or energy of the wave in distance divided by time. The wave base is the spot below which the water is undisturbed by wave activity. The fetch is the distance involved in the blowing of any wind. A long fetch means the wind energy was strong. Figure 60 shows wave anatomy in detail:
Figure 60.
221
