Oceanography (2+1)

Spilling and breaking waves

Breaking waves

Breaking waves are otherwise called breakers. These are found in all beaches. Some waves are destroyed by opposite winds, others interact and some cancel each other, and most of the waves end up as breaker, when they encounter shallow water. Most waves move across the surface of the deep ocean unaffected by the bottom. As waves approach the coast, they are increasingly affected by the bottom, and they change from deep water to shallow water waves. Wave length and speed decrease, while the wave period remains constant. At the same time the wave height decreases slightly and the finite energy is converted into potential energy and its height increases rapidly as water depth decrease to one tenth the wave length and the wave crusts found close together. The crust angle reach the critical value of 120⁰. The proximity of the causes once circular orbit to become elliptical further adding to the waves   in stability. In deep water a molecules in the crust stop its orbit can count on support from the water immediately in front of it to complete its cycle. As the breaker shoals, there is not enough water immediately in front of the crust to come all the way up to meet it. The crust appears to get ahead of its support and it breaks. The wave break when the velocity of the water molecule in the crust is greater than that of the wave beneath such that the crust gets ahead of the wave.

            Waves often break more than once before reaching shore. Breaker are classified in to four kinds

Types of breakers:

1. Spilling breakers

2. Plunging breakers

3. Collapsing breakers

4. Surging breakers

Spilling breakers: These are over steepened waves where the unstable top spills over the front of waves as they move towards a beach. In spilling breakers waveforms advance but  wave heights are diminished. These waves break gradually over a considerable distance.

Plunging breakers: The wave crust typically curls over, forming a large airpacket, when a wave breaks, there is a large splash of water and foam  which is usually thrown into the air. These plunging breakers tend to form from long gently sloping but irregular bottom.

Collapsing breaker: Break in the middle or near the bottom of the wave rather than at the top.

Surging breaker: In surging breaker the waves slides up and down the beach with little or no bubble production. These are common is areas with steeply sloping bottom.