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The Effects of Waves on Sand Erosion

Waves from the sea play an instrumental role in shaping the shorelines of the world. Over hundreds and thousands of years, they can transform sandy beaches into different forms. Because waves almost never crash on shore at a 90-degree angle, they toss and tumble grains of sand along the shore, moving the beach incrementally until the sand is deposited in another location.

Sand Transport
- When you wade into the water at a beach, you'll notice that the sand on shore is fine, then it becomes coarse near the point at which the waves break, then it becomes fine again in deeper water. As waves crash ashore at an angle, they will push sand in the direction of the wave then pull them back toward the sea. Over time, the sand particles make their way down the beach, either resting on the sand bed or suspended in the water, or it can find itself pulled back into the sea.
Tombolos
- Tombolos are thin, sandy structures that connect an island to the mainland. The island is then called a tied island. They are formed when sand is deposited from two opposing currents enough to accumulate between the island and the mainland, though they can be eroded or washed out altogether in strong storms. Wave refraction is responsible for these landforms. This is when a wave has its direction changed by the shallow water surrounding an island, which splits the wave into two sections, which then collide diagonally. Sand then accumulates along this path, and the island is connected to the mainland.
Graininess
- The size of sand grains affects the slope and shape of a beach. Coarse beaches drain into the beach face, which then reduces backwash. This means that sand is carried further onshore by the waves, but are not dragged back towards the sea, which results in a steep beach. Beaches that have finer sand stay waterlogged, which means that waves remove any loose sand with its backwash, and the slope of the beach is very light. Tides affect the shape of a beach as well; the greater the range of the tides, the shallower the beach slope will be.
Wave Swash
- The amplitude and length of waves play an important role in shaping beaches. A wave has three stages as it approaches the shore, first becoming a breaker, then a bore, and finally a swash. When a swash washes up on a reflective beach, that is, a beach with a steep face, they will be short bursts with short swash lengths. Conversely, flatter beaches have longer swash lengths with longer periods between waves.

Nature