CHAPTER 10: COASTAL PROCESSES, PATTERNS AND LANDFORMS
Factors controlling wave height over open water
wind speed
wind duration fetch
Fig. 4 Wave sailing in strong winds Belmullet, County Mayo
When waves break, water rushes up the beach. This is known as the swash. Some of the water will seep into the sand, the rest returns to the sea as the backwash.
Swash leaves material on the beach. Fig. 5 Swash and backwash Constructive waves (spilling breakers) – building up our coastline
Some waves have a powerful swash that can carry debris up the beach but have little energy left in the backwash to drag the debris away again. These are called constructive waves. A wide sandy beach is the best evidence of deposition by constructive waves. Constructive waves break some distance from the shore, and the surf rolls in gently up the beach.