The Mam Tor Creeping Landslide

Abstract

The Mam Tor creeping landslide has been active throughout the 3600 years since its formation. The landslide is divided into three main sections; an upper extensional regime at the head, a central strike-slip regime, and a lower compressional (in the downslope direction) regime in the toe. This movement picture within the slide has been revealed through annual surveys over a 19-year period. Maximum local displacement rates in excess of 50 cm/yr have been measured. Local faulting within the slide, driven by the heterogeneous distribution of displacements within the main body of the slip gives rise to a hummocky, irregular topography across the whole slipped mass. Year-on-year movements prevent a normal dendritic drainage system from developing, and local streams drain into isolated ponds with no natural outlet. Discrete periods of movement, as identified from high resolution monitoring using underground creep meters, are typically initiated by high rainfall over a period of 3–4 weeks before creep can begin, but movements are normally suppressed in the summer months as a result of evapotranspiration by vegetation cover, returning one-third of rainfall to the atmosphere. The Mam Tor slide is the only active one of five of similar dimensions in the vicinity.