Stabilising the Beaches

The two main factors that imapct on beach erroision rates are wave climate and sediment size.
The only way to reduce the waves impacting on Eastbourne and Pevensey is to block them with a barrier. co-park.
This is possible and such engineering solutions have been applied successfuly elsewhere, such as Borth on the Welsh Coast.

Sediment Size Matters

The beach above is in state of quasi-equilibrium
It has been naturally filled with sufficent grey cobbles to reach this state.
During the winter of 23-34 this and eleven other stabilised beaches remained intact during the twelve named storms that impacted on the coast.
This is dramatically contrasts the adjacent beaches filled with dredged ballast s that required three major interventions over the same period.

Grey Cobbles

The grey cobbles washed out from fallen chalk deposits appear to absorb the incident wave energy and change state (position) over relatively short distances when impacted by storm waves.
Cobble size clasts that are washed down-slope become less influenced by gravity and remain stationary until storm waves wash them back up slope, generally towards the eastern groyne of a particular beach cell.
The slow accumulation along the eastern groyne eventually tops the groyne structure and further input results in over-topping into the adjacent beach.
The ballast that has been used to infill the beaches is lost in the same manner, but a significant portion of the recycled ballast is drawn down the beach and settles lower down between the groynes. The slope between the base of high tide berm and beach toe forms into a relatively hard flat sloping surface, due to the sediment mix.
Wave energy entering between two adjacent groynes is partially reflected by the groyne structure. Interfering wave trains distribute the energy in a a chaotic manner which results in high and low energy sectors across the beach. As the tide recedes these low and high energy sectors are depicted by the sediment distribution.
The chaotic mix of sands, gravel and cobbles is sorted by random wind and wave conditions. Most of the sediment grains are of insufficent size to resist being moved by the wave energy vectors and are partially sorted by wave action and backwash
The beach below has been naturally recharged with grey cobbles and is now able to absorb wave energy without any significant change in state. The slow drift to the NE corner of the beach can be reversed, on a beach by beach basis using clean energy.

Local sources of the more suitable grey cobbles have been identified and these offer a solution to the above.

A significant clean deposit are located along the foot of the cliffs between Beachy Head and Birling Gap. A method of moving them to the beaches to the east has been developed using predominantly green energy.

The grey cobbles "lost" between 1985 and 1999 cannot have moved far from the beaches due to the energy required to move them along a near horizontal surface that exist along the low tide zone. It is very likely that they have become assimilated within low tide sands that are deposited over the bedrock.

Recycled Ballast

It has been proven empirically using photographs and basic survey techniques that the rate of beach erosion has increased significantly due to the ballast used to recharge the beaches since 2004.

The beach below is eroded by several agents including direct wave energy, vibrations from close by breaking waves, fore-wash and rain. The significantly quantity of sand is washed out and is eventually deposited within the low tide zone. Small round brown pebbles are easily displaced by wave action and roll down the flat sloping, relatively smooth inter-tidal seabed. Negative loops are introduced to the beach erosion process as the recycled sediments are reworked by wave action.

In general the large cobbles are moved along the beach slope toward the NE corner and the smaller grains (sands) either carried away in suspension or deposited at the low tide zone. Small round pebbles are drawn-down and build up the beach surface that slopes upwards towards the east side of the beach