Akademik Veri Yönetim Sistemi
JOURNAL OF COASTAL RESEARCH AN INTERNATIONAL FORUM FOR THE LITTORAL SCIENCES, cilt.26, sa.SI, ss.72-81, 1998 (SCI-Expanded)
Some 35% of the England and Wales coastline has been designated as Heritage Coast, with the aim of preserving for
posterity, the natural scenery. The Glamorgan Heritage Coast is mainly cliff bound and the cliffs are composed of
Lias limestone and mudrock with rock mass strengths of 123MN/m2 and 12MN/m2 respectively. Three main sets of
readily apparent joint patterns characterise the area i.e. W-E; NNE-SSW; NW-SE, but myriads of Griffith cracks
further reduce intact rock strength. Cliff mass failure is a widespread occurrence and four movement mechanisms
exist?translation, toppling, buckling and joint block detachment. Questionable engineering practises have been ini
tiated at Colhuw Beach which have further lowered rock strength and exacerbated rock failure. Cliff blasting was
employed to reduce the upper cliff angle and to generate a talus cone of some 150,000 tonnes. This procedure was
predicted to reduce the frequency of failure, slow the rate of recession and protect the cliff base from erosion. However,
the blast debris was swept away by high wave energy and efficient longshore drift within five years, and as much
energy from the blast went into the rock face opening joint systems, enhanced recession has continued. Similarly the
1997 partial sea-wall and revetment construction projects undertaken at the same location with the aim of protecting
recreational facilities, have had suspect results since the natural characteristics and behaviour of the system were
not fully appreciated. A reliability?based risk model (REBAD) has been applied to this project and concluded that
within 15 years, the moderate damage level of 15% will be exceeded with 80% probability in the revetment.