South Downs Coastal Group
A description of the Coastline covered by the South Downs Coastal Group.

The shoreline covered by the South Downs Coastal Group spans some 84km of East and West Sussex, on the south coast of England.

The various types of natural and man made features are shown below, as are a few of the types of defences.

From Beachy Head, with high chalk cliffs, in the East to Selsey in the West the shoreline forms a long sweeping bay.

A recent massive rock fall can be seen in the foreground. Little active management is undertaken; the is no development at the cliff top and the gradual but continual loss of material is seen as a natural process that should continue. There is some benefit to coastal processes from cliff falls in the area, not from the chalk that temporarily accumulates at the foot of the cliff but more from the flint that is often contained within the chalk. The flint lasts longer in the system than chalk as this quickly degrades and dissolves.

 

Here Selsey Bill can be seen in the top of the frame with the mouth Pagham Harbour in the mid-ground. The shingle spits and bars can clearly be seen even though the shot was taken near high water. The site is a Site of Special Scientific Interest, Special Area of Conservation, Special Protection Area and a Ramsar site. It is an important site for nesting Terns and the shingle ridges support colonies of Yellow Horned Poppy and Childing Pink. In the foreground can be seen part of Pagham Lagoon
What is now Pagham Lagoon used to be the outlet to Pagham Harbour in the late 1800s and was formed when the migration of the shingle spits sealed the outfall to the sea. Another coastal lagoon can be found at Shoreham, where Widewater supports a various species of flora and fauna.

A number of rivers discharge to the sea along the frontage; notably the Cuckmere at Exceat where the artificial cut made in 1846, the disconnected meanders can be seen in the foreground.

This area is being examined as a site where a more natural and sustainable defence can be established; controlled breaches are to be formed in the banks and areas of pasture allowed to flood and revert to floodplain, the meanders may also later be re-established, by reconnection to the main channel. In the middle of the frame is Seaford Head and a little further west is the town of Seaford.

Beyond Seaford is Newhaven.

Looking back eastwards, the port of Newhaven is on the River Ouse. The main port operation is a cross-channel ferry to Dieppe and the approaches are regularly dredged to allow these ships to operate.

Seaford is at the top of the frame and Peacehaven, in the foreground, is on the Greenwich Meridian (0 longitude).

Seaford, has a wide shingle bank, regularly recycled by the Environment Agency, to provide a defence against the prevailing south-westerly storms which attack with great force.

Whilst the area to the east of the Ouse is low lying, the land to the west is relatively high and continues to be so through to Brighton - a distance of approximately 13km.

There are few defences along the eastern part of this shoreline, although to the west the undercliff is protected by a concrete seawall and several rock and masonry groynes.

In the foreground is Rottingdean and towards the top of the shot is Brighton Marina.

The coastal plain beyond Brighton rarely rises more than 10m above High Water near the shoreline. Many of the coastal towns grew up around the turn of the last century due to the tourist industry and the belief in the health enhancing coastal airs.

Much of Brighton is fronted by a wide shingle bank, especially the area immediately west of the Marina. There are a number of large masonry groynes in the main beach and these generally give way to a more traditional timber groynes in the west.

The coastline was protected by ad hoc defences in the 1800s; prior to this the coast was typically eroding,by as much as 2½m per year. With the increase in development in the 1920s & 30s came a more concerted effort to defend the coast against erosion.

 

Brighton Marina was constructed in the open sea, from precast concrete caissons sunk to the seabed, in the early 1970s. The Marina now supports high quality residential property and various retail and leisure units. It has a large pleasure craft mooring facility; fishing and dive boats also operate out of the Marina.

Approximately 7km further west Shoreham Harbour supports a more commercial operation, with timber and aggregate ships regularly discharging their cargoes. This commercial operation exists alongside a smaller pleasure sailing fleet.

The locked harbour is on a spur of the River Adur, which is controlled by two harbour arms. Shingle builds against the western arm and material is by-passed eastwards to help reinforce the narrow, timber groyned beach fronting the Harbour.

Here, at Birling Gap, where the high chalk cliffs of the South Downs meet the sea at the eastern end of the frontage, an old dry river channel presents a weaker defence than the surrounding chalk cliffs.

The resulting increased erosion has provided an area where there are conflicting opinions. Whether there should be human intervention to safeguard the small number of properties on the cliff-top or should the natural process of cliff recession continue to safeguard the this Site of Special Scientific Interest.

Unfortunately for those living on or near the cliff-top, economic considerations also come into play; the benefit of defending the coast must be weighed against the cost, now and in the future, of providing a defence. This is true of the whole coastline.

With a few exceptions, the western part of the frontage is defended by timber groyne fields, often backed by concrete seawalls. Here, at Worthing in common with many other areas, development has nearly up to the shoreline. Timber groynes can be seen developing the familiar ziz-zag pattern of shingle, as they reduce the rate at which shingle is carried along the coast.

To the west of the frontage the inter-tidal area and the seabed beyond slope very gently, producing a wide (up to 500m) foreshore, much of which is covered with a veneer of sand over the chalk bedrock. Beyond Bognor Regis Regis this chalk gives way to London Clay, interspersed with Reading Beds (shingle) and harder sandstone outcrops.

Aldwick Bay, in the foreground, has a naturally accreting beach giving way further east to the timber groyned beaches of Bognor Regis, Felpham and Middleton.

Many of the defences fell into disrepair during WWII and it was not until the introduction of the Coast Protection Act in 1949 that many coastal defence systems were again brought back into good order.

Today, where appropriate, the "hard" defences of concrete seawall and timber breastworks are being replaced with the "soft engineering" of shingle beach management systems and rock structures.

Whilst the rock used is in itself hard, the defence systems constructed with it and the wider shingle beaches are considered "soft" because they absorb wave energy, rather than reflecting it with seawalls, as in the past. Wave reflections encourage scour to occur and thus remove beach material from the shoreline.

Rock has been used in an number of innovative project as in the scheme seen here at Elmer. The old timber groynes were unable to efficiently maintain a suitably wide shingle beach, due to the increased sediment transport rates caused by the change in beach plan shape.

The rock breakwaters reduce wave energy whilst allowing some littoral drift to continue. The scheme was a joint project between the local authority and the national Rivers Authority (Now Environment Agency) and cost around £6m, in a number of phases. The main one being constructed in 1992/93 and involving 200,000 cubic metres of imported shingle and 100,000t of rock

Here at Climping the end of the Elmer scheme can just be seen in the foreground, giving way to the largely open beach which fronts the strategic gap between the conurbations of Littlehampton and Bognor Regis.

High quality farmland is a key feature of the coastal plain in the west of the area.

 
For more information about the content of these pages please contact coastal.defence@arun.gov.uk.