Past and Present Rates of Coastal Chalk Erosion at Peacehaven, Sussex
by Richard Charman
Abstract At Peacehaven, in East Sussex, a classic example of a chalk shore platform is found at the foot of cliffs defended by concrete sea walls and groynes. Two sites on the platform were studied in this document, based around two groynes at the west and east of the town. The cliffs behind these sites were found to be retreating at 0.332m per year until the defences were constructed, as many of the houses were close to cliff edge. The platform is continually downwearing via a variety of processes but in this document, it is found that it is greater in the runnels (water and shingle filled gullies) than on the ridges. Longshore drift causes the eastern sides of groynes to be more exposed, increasing erosion due to the continual removal of the coarse material. On the western sides, material tends to build-up, protecting the platform surface. Along the lengths of the groynes (which vary between 35 and 50 meters long), erosion is fastest close to the sea wall and approximately 20 to 25 meters from the sea wall. It tends to be slowest approximately 15 to 20 meters from the sea wall. Three methods were used for measuring the downwearing: a micro-erosion meter (MEM), screw and washers attached to the platform and designed to block denudation beneath them and the groyne structures themselves, which have blocked the denudation since they were installed 18 to 24 years ago.