Welsh Journals

THE FREOUENCY OF LANDSL/DES IN THE SOUTH WALES COALFIELD W. C. Rouse CAMBRIA INTRODUCTION The problem of landslides In the South Wales coaifield has been recognised since the early years of the present century when several examples of landslipping afiecting persons and property were recorded and investigated (Knox 1927). A new awareness of the importance of slope stability began In the late 1960s with a riee In interest in processes operating on slopes by both geomorphologlsts and englneers together wtth conferences highlighting the englneering properties of slope materials and the civil engineering problems assodated with areas of landslipping in the region (Simmons 1970; Perkins 1980; Morgan 1985). Investigative reports by members of the Geotogical Survey into landslipping in South Wates have also appeared in the last decade (Gostelow 1977; Conway et al. 1983) and further work is proceedlng wtth the current investigation of acoustic emissions from landslides (Stytes et al. 1988). This short paper reviews the concept of slope frequency and valley side stability In South Wales using primarily published data, but also unpublished reports of the Deptartment of the Environment and personal communications from consulting engineers and fellow research workers.The implications of the findings are then discussed and the possible dangers inherent in transport, industrial and urban development in the South Wales CoaJfield are highlighted. Rouse W C. (1989) The frequency of landslides in the South Wales Coalfield Cambria, 15, 167-179 ISSN 0306 9796. ABSTRACT About 93% of the landslides in the South Wales coalfield are shallow failures, confined to the surface deposits, and translatíonal in nature. These landslides are particularly frequent in areas character- ised by thick superficial deposits, rock strata that act as aquifers and aquacludes, and over-steepened valley sides. A cooiparison of threshold slopes and slope frequency diagrams suggests that extensive areas of the South Wales Coalfield are susceprible to landsliding and old shear surfaces exist even in areas with little surface manifestation of failures. Old landslides have been reactivated for several reasons, one of the most important being the change in the rainfall intensities since about 1925. AUTHOR'S ADDRESS Dr W. C. Rouse, Department of Geography, University College of Swansea, Single- ton Park, Swansea SA2 8PP, Wales. (Paper received October 1988 revised paper accepted October 1989)