PRediction of the erosion of cliffed terrains : "PROTECT" : technical report

PROTECT (Prediction Of The Erosion of Cliffed Terrains), is a European 5th Framework part funded research programme undertaken by the national geological surveys of Denmark and Greenland (GEUS), France (BRGM) and the U.K. (BGS) and the University of Brighton, supported by the French Geotechnical Laboratories at Nancy (INERIS). BGS are the co-ordinating partner. Rocky, coastal cliffs of North West Europe are continually subjected to changes in stress caused by marine erosion and climatic factors. This leads to fresh geological features and materials becoming an active part of the cliff instability regime. To investigate the possibility of providing better ways of predicting when, where and how cliff instability would occur, chalk cliffs were chosen by the PROTECT team. Chalk cliffs form extensive coastlines on the Baltic coast of Denmark and along the English Channel coasts of northern France and southern and eastern England. These are in areas where, either communities are built on the cliffs (Mensil-Val, Criel, northern France) or the cliffs are open to public use (Beachy Head, U.K. with >200,000 visitors a year; Møns Klint, Denmark with similar number of visitors) under and on top of the cliffs. A further advantage of choosing chalk cliffs is the level of previous research carried out under other European funded programmes such as ROCC (Risk Of Cliff Collapse) which made selection of the PROTECT sites easier. The PROTECT programme set out to investigate new ways of (i) determining the temporal aspects of movements in the cliffs leading to collapse (ii) identifying the failure mechanisms. This required integrating the detailed engineering geology with the results from the geophysical techniques and the rock mechanics testing. The PROTECT results indicate that each geophysical technique is suited to a particular type of geology, but not to all the geological situations investigated. Hence, the detailed engineering geology is an essential prerequisite to the interpretation of results and the application of the techniques.