A Level Geography - Coasts Exam Questions

Explain how different wave types result in different beach profiles [6 marks]

Different wave types can result in different beach profiles. Waves can either be constructive or destructive and this depends on the strength of their swash and backwash. When the swash is bigger than the backwash, it is a constructive wave; when the backwash is bigger than the swash, it is a destructive wave.

Destructive waves have larger backwash than swash, meaning that more material is removed from the beach than added. They are usually formed where there is a large fetch during storms, meaning they are powerful and tall, and have a high frequency. An example of a place that gets destructive waves is Cornwall. Destructive waves remove material from the beach and produce a steeper beach profile because of this. They carry material out to sea which means the gradient of the beach is likely to be more vertical. Destructive waves can form a storm beach which happens when waves have a very large fetch, so they can deposit larger material higher up the beach which can then not be removed with the swash. This creates a steep beach profile.

Constructive waves have less power and are likely to be smaller compared to destructive waves. They have a low wave frequency also. Because constructive waves have a bigger swash than backwash, more material gets pushed onto the beach so more is always added, meaning that the beach will have a smoother, gentle beach profile. These waves continue to deposit more material on the beach than they remove which will then lead to the creation of a berm, which happens at the high tide mark. These factors create a shallow beach profile which is more smooth and gentle than one created with destructive waves.

Explain the part played by longshore drift in the development of coastal landforms [8 marks]

Longshore drift is the process which moves and transports sediment along the coast. Waves move material along the beach in the direction of the prevailing wind and then gravity pulls the material down the beach at right angles to the coast. Some things can interrupt this which leads to the formation of coastal features like tombolos, spits and drift aligned beaches.

A spit is a stretch of sand or shingle that extends from the mainland, out to sea. It happens where the coast changes direction so the wind blows at a different angle to the coast, for example, at a river mouth. Longshore drift continues to deposit sediment across the river mouth which creates a bank of sand, known as a spit. The shape of this can change as a result from the refraction of waves, for example, the spit may curve in on itself like at Dawlish Warren. Waves may return to their normal direction; strong winds can lift sediment which can form dunes, meaning that the spit can stabilise and become home to pioneer plants.

Longshore drift can also develop drift aligned beaches. This happens when the waves break at an angle to the coast, causing the swash to occur at an angle. The backwash runs perpendicular to the beach. The sediment is pushed up the beach at an angle, however, gravity pulls the wave back down the beach at a right angle to the coast. This means that the sediment is pushed along the beach, creating a thin beach that is long. An example of a beach like this is Dawlish in Devon.

A tombolo is a beach that has been formed between a small island and a mainland. They occur due to wave refraction and diffraction as when waves come close to an island, they are slowed by shallow water. They are forced to bend around the island which creates longshore drift on the opposite side. Sediment will slowly begin to accumulate in this location and the waves will bring sediment onto this ridge from both sides. Over time, more sediment will keep on getting added, and when it connects the mainland to said nearby island, a tombolo is formed. It may be covered at a high tide. There are examples of this in Britain, namely at Chesil Beach where the Isle of Portland is joined to the mainland.

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