The coastline from Brighton to Eastbourne is a delight for any coastal engineer, and I am no exception, for it features almost all the important innovations of coastal engineering, along with old and new techniques used in the preservation of the beaches and harbors, endangered by natural and human encroachment. In other words such a place is an engineer's delight!
Walking along the Brighton Marina is an exhilarating experience and I was once again struck by the way in which this development has been made possible. Economic activities and urbanization though, have had some very adverse effects on the environment and coastal erosion is the cause of great concern. The Brighton Marina caused depletion of the beaches because it altered the long shore drift, and Seaford that was already suffering from erosion was further affected.
The Groynes had been built as early as 1836 to combat this problem and increase the amount of shingle. A groyne can be built of wood, concrete or rocks, which are placed at right angles to the sea, and help to create a wider and well nourished beach, since it catches the shingle on the updrift side, and protect the coast because the filtered sand absorbs the wave energy. But there is loss of beach material on the down drift side creating the need for another groyne there.
At Brighton a sea wall and promenade were built at the foot of the cliffs in the 1930s, with the sea wall constructed of concrete blocks and the space between the wall and the cliff was packed with the chalk rubble, which was removed from the cliff, while constructing the wall. A splash wall and promenade were laid on top of this and Groynes were constructed at right angles to the sea wall, which trapped the shingle, and was further extended to Saltdean. At Brighton and Hastings the groynes are made of stone and cement and are much more elaborate. (Bosworth, 1909) These hard engineering techniques were successful to a certain extent, in combating the coastal erosion which has grown considerably.
A number of breakwaters have been built to defend the coast and to prevent anchored yachts and ships from the effects of long-shore drift. The caisson unit is used here and they are characterized by vertical sides, where the mass of the caisson and the filling inside is used as a resistance against the waves. This is also effective in those places where one or more vessels are berthed on the breakwater's inner sides. (N.W.H. Allsop (2002).
The effect of the waves, leading to soil erosion have been checked by the dollos, near the Marina, and this is highly resistant to wave action and there was much better results when compared to the enormous concrete blocks which were earlier sunk offshore to catch the impact of the waves and tides. The breakwater at Newhaven, built more than hundred years back, has been effective in countering the eastward littoral drift of the shingle. The shingle buildup on the west of the breakwater has strengthened the cliffs below the Newhaven Fort, but the erosion in the bay led to breaches of the sea wall at Seaford.
Beach nourishment, as a method of coastal defense is