Brighton & Hove's coastline is fully defended and so the usual effects of coastal processes (erosion, deposition, movement of beach material etc) are limited here. A general description of coastal change is given on Defra's website.
Brighton & Hove's coastline is divided into 2 sections by the Marina at Black Rock :
West of the Marina
The dominant wind direction is south westerly, so shingle and sand is moved eastwards by a process known as longshore drift. This effect can best be seen at groynes where the shingle builds up against the west side and is lower on the east. This position reverses after a run of easterly winds.
There is very little natural feed of shingle onto Brighton & Hove's beaches due to the mouth of the river Adur. The principal source of shingle onto our beaches is from Shoreham Port Authority's regular recharging of their beaches. They take shingle from their section of beach on the west side of the River Adur and bring it by lorry to deposit on their beaches on the east side. This shingle then gradually migrates along to the Marina. Consequently the size of the beaches gradually increases as you go eastwards.
It would be easy to assume that the Marina acts alone as a large groyne stopping beach material from moving further east. However, photographs taken prior to the construction of the Marina show that the beaches in the Kemp Town area were already growing in size. At one time the sea came right up to the south side of Madeira Drive where there still exists a sea wall, now buried. In even earlier times the sea washed the cliffs that now stand behind the concrete wall on the north side of Madeira Drive.
The angle of the seabed changes at Black Rock becoming steeper to the east.
East of the Marina
The coastline to the east of the Marina is dominated by chalk cliffs and a wave cut platform. The Undercliff Walk built before World War 2 to defend the cliffs from erosion was gradually renewed in the 15 years up to 2005. The first defence structures were built around 1907 to prevent the cliffs receding with the resulting loss of the coast road and the old trunk sewer which runs eastwards just within the cliff line at beach level. Due to the effect of the Marina and the changes in water depth east of Black Rock very little shingle comes onto this section of coast. This means that large beaches do not naturally form against groynes so a seawall was built to defend the cliffs from erosion. The beaches at Rottingdean and Saltdean have been created from imported beach material for leisure as well as defensive purposes.
Beaches in the south east are regularly surveyed, the results are freely available from the Channel Coastal Observatory at www.channelcoast.org