The importance of preserving Italian hilltop towns through a general geotechnical strategy is discussed and is followed by a specificreview of the hydrogeologicalconditions responsible for regional mass movements at ancient hilltop towns in Basilicata. A historical survey of reactivations in colluvial deposits at selected sitesin the region suggested that increased activity was taking place in response to extreme rainfall events, possibly related to long-term climatic changes. The importance of natural and anthropogenic processes along critical hydrogeological boundary conditions in relation to this activity is then reviewed and one example of urban landsliding from Grassano in the Basento valley is described. Local structure, such as faulting, was shown to be especially important in the location of both groundwater discharge (springs) and the landsliding. The landslide activity in the town was also shown to be related to a period of population expansion and possible domestic water leakages following the provision of a pumped supply. It is suggested that these anthropogenic processes reduce the usefulness of empirical links between landslide frequency, rainfall extremes or other explanations involving climatic change. Finally, a strategy for landslide management based on the use of hydrogeological conceptual models and GIS technology is proposed.

Hadleigh Cliff forms part of a line of abandoned London Clay slopes, rising to a height of generally + 40 m o.d. or more, which extends westwards from Southend-on- Sea. The cliff, with its toe level originally at about —19 m o.d., was formed by strong fluvial erosion in the Middle and Late Devensian. By the latter part of the Late Devensian erosion had virtually ceased and since then the cliff has degraded in an episodic manner, largely in response to climatic changes. Four main stages of degradation, with intermediate periods of relative stability, have been recognized and dated, as follows: (1) Late-glacial, periglacial mudsliding, associated with a toe level of —19 m o.d. (2) Early Atlantic, temperate mudsliding, associated with a toe level which was rising with the continuing Flandrian aggradation, but lay on average at about —9m o.d. (3) Early Sub-Atlantic, temperate mudsliding, taking place to the present toe level of about + 3 m o.d. (4) A late 19th century, moderately deep-seated landslide in the crest of the slope, possibly caused in part by human interference. The times at which the first three of these stages of degradation occurred are believed to represent periods of generally increased mass movement activity in much of Britain and Europe. The present morphology of Hadleigh Cliff comprises a straight 20 scarp at the crest, an irregular and actively unstable 11° degradation zone, fronted by a smoother, quasi-stable accumulation zone inclined at about 8°. From a knowledge of the volumes and dates of the various colluvial units mantling the slope, reconstructions of earlier positions of the cliff profile are made. These indicate that during the last 10 000 years the inclination of the combined degradation zone and crest scarp has declined from about 19° to 13°, while that of the accumulation zone has remained relatively constant. The accompanying recession of the cliff crest has been approximately 50 m. From the pattern and dating of the various stages of colluviation, which increase both in age and in degree of fabric breakdown from crest to toe of the slope, it is clear that the cliff is degrading from the top. This is also reflected in the fact that the zone of weathered, in situ London Clay beneath the colluvium diminishes in thickness, in general, from bottom to top of the slope and is entirely absent beneath the late 19th century landslide. In an average year the potential evaporation at Hadleigh exceeds the rainfall. As a result soil moisture deficits are unusually high and appreciable pore-water tensions in the capillary zone probably exist even at times of maximum seasonal piezometric levels. Account is taken of these in the stability analyses that are carried out, which indicate that the accumulation zone has a factor of safety of around 1.05 in com­ parison with the value of unity obtaining in the currently unstable degradation zone. A comparison between the values of (pT indicated by the back analyses and those measured on the Hadleigh colluvium in ring shear shows the latter to be appreciably the lower: the discrepancy is reduced if the effects of pore-water tensions in the capillary zone are allowed for.

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A section of the road route chosen for the Ironbridge bypass crosses the northern valley slopes of the River Severn, near Buildwas, Salop. The slopes are underlain by Silurian Wenlock Shale which have been affected by slope degradation dating from the end of the last (Devensian) glaciation. The road design included cuttings and a large embankment up to 20 m high and circa 300 m long which was constructed across landslipped ground. This paper describes the engineering geology of the shale and the slopes, and draws particular attention to the difficulties of selecting critical potential failure mechanisms where there are complex, periglacially disturbed ground conditions.