Sandy beaches tend to be wide with gentle profiles, such as Swansea Bay which is 500m wide and has a gradient of 1:50. This is due to the low permeability of the sand as the fine particles leave little space for the water to drain through. This means that only a little of the swash is lost through the sand and low frictional loss of energy over fine material resulting in material is distributed up and down the beach evenly. Off shore bars develop on sandy beaches encouraging the wave to break earlier reducing swash energy and the sand absorbs wave energy encouraging more spilling breakers.
Shingle beaches tend to be narrow with steeper profiles such as Aldburgh which is 70m wide and has a gradient of 1:10. This is due to the high permeability, so much of the swash is lost through the coarse material. This coarse material causes high frictional loss of energy the shingle meaning that the swash is stronger than the backwash so the material is pushed up the beach resulting in it being distributed unevenly up and down the beach. The steep gradients created by this reflect the wave energy and encourages the more destructive plunging breakers. This encourages berms to develop at the point where the wave is at highest energy resulting in storm beaches and high tide ridges.
As well as the sediment having a role of shaping beaches, the dominant wave type can also influence the beach profile. Constructive waves, which are swell wave from a long fetch, are long, low in relation to length and relatively infrequent with 6-8 arriving in a minute. These types of waves are commonly found on low gradient beaches and tend to break near the shore and as they have travelled across such a large distance the energy of the waves is dissipated allowing the sediment to remain on the beach. Whereas destructive wave, which are local storm waves with a short fetch, are short, high in relation to length and are more frequent with 10-12 arriving in a minute. They are most commonly found on steep gradient beaches and as the energy is concentrated in a relatively small area, the strong backwash strips sediment from the lower beach, steepening the gradient further.
This illustrates the concept of equilibrium by exhibiting the balance between particle size, gradient and dominant wave type.
Beach profiles aren’t the same all year round, they can vary over time. Beaches can change overnight with high tides pushing the coarser material into high tied ridges and sweep zone changes can be driven by certain events such as a storm. This can change a beach profile dramatically and make many negatively changes. Beaches can also changes over a longer period of time such as seasons. In winter, when storms are more frequent, destructive waves are dominant and beaches can be stripped of material. For example Swansea beach dropped by a meter during one winter season, and Aldburgh beach, a steep shingle beach, lost over 2 metres. Seasonal change isn’t only limited to the UK, beaches in India display dramatic alteration between monsoon and non-monsoon seasons. Over a period of years beaches can change due to the littoral cell system. Barton on sea lost its sand supply due to big groyne being built in Bournemouth to control their problems with longshore drift. On the east coast of the Furness peninsula there was a consistent loss of beach material when new sea walls were built at Roosebeck to control erosion. With no erosion there was no new sediment being added and longshore drift continuing, beach levels decreased.
Beach plans can tell how beaches are shaped and are maintained by the view from above. There are 3 main shapes a beach can take. Swash aligned beaches are beaches where waves are refracted between headlands and approach the shore at right angles, with wave crests parallel to the beach. The dominant movement of material is up beach, swash, and back down the beach, backwash. This creates stable features and although the profile may change due to changes in the sweep zone processes, the plan alters very little as there is no appreciable net gain or loss of material.
Drift aligned beaches are where wave approach the coast at an angle. Longshore movements of sediment build out the beach to ensure that the optimum angle for sediment movement is achieved (40⁰-50⁰). Sediment is added at the same rate that longshore drift is happening so that no material is lost.