Movement of the Mam Tor landslide, Derbyshire, UK

The Mam Tor landslide is a kilometre-long feature in shales and sandstones. The initial slope failure occurred over 4000 years ago as a rotational lan dslide that developed. into a large debris flow at its toe: A road built ac ross: it nearly 200. years ago, and now closed, provides graphic evidence o f continued movement of the slide mass; this has:: now been monitored for e ight years; Current. mean annual movement. is upto 0.25 m; this increases g reatly when winter rainfalls exceed thresholds of both 210 mm/month and 750 mm in the preceding six months, The most rapid movement is now taking plac e in a central zone of:slide blocks that rest on a steep slip surface locat ed at or close to the buried ground surface just downslope of the initial f ailure: toe, Both the main upper mass of landslide: blocks: and the debris toe move more Slowly over basal shears at lower angles of dip. Deep drainag e of the central part of the Landslide would be the mast effective means of stabilization, but may not totally eliminate movement.