Beaches

Many people don't realise it, but beaches are a in fact a landform of deposition caused by the sea and its sediment. They can form in many different types of coastline and bring immense enjoyment and satisfaction to many of those who use them.

Beach profiles generally fall into two extremes: those that are wide and flat (constructive) and those that are narrow and steep (destructive). The type of beaches depends on the wave energy and more specifically, the type of wave. The types of wave include;

 - Constructive waves. These wash sediment up the beach as the waves have high energy, they then deposit the sediment as the energy of the wave decreases and it flows back down as backwash and out to the sea. They are usually shallow and of a low frequency. It involves a strong swash and weak backwash, as well as a long fetch (the horizontal distance over which wave-generating winds blow).

 - Destructive waves. These pick up sediment as they run down the beach and carry it back out to sea, therefore 'destroying' the beach.  Often involve high waves and they are often of a high frequency. They have a strong backwash and a weak swash, as well as a short fetch.

(NOTE; swash - the rush of seawater up the beach after the breaking of a wave.

            backwash - The motion of receding waves, as water flows down the beach)



The type of beach also depends upon the particle size. There is a relationship between particle size and the beach slope profile; this is partly to do with grain size but also to do with percolation rates.

As a result, different beaches will have different features associated with them. For instance, destructive waves often produce steep beaches whereas the beaches formed by constructive waves are often much more gently sloping. Or, shingle beaches are steeper than sand beaches because shingle beaches have higher percolation rates.

Constructive waves (top) and Destructive waves (bottom. Images from BBC.