UNDERSTANDING RAINFALL-LANDSLIDE RELATIONSHIPS IN MAN-MODIFIED ENVIRONMENTS - A CASE-HISTORY FROM CARAMANICO TERME, ITALY

The expansion of Caramanico Terme in this century has led to the urban ization of marginally stable valley slopes, and this has coincided wit h the apparent acceleration of landslide processes. Recent landslides on man-modified slopes were caused, but not necessarily triggered, by heavy precipitation (antecedent moisture was a more critical factor th an the amount of storm rainfall). Because no important landslides on n atural slopes in the same period were reported in the Caramanico area, a clear distinction must be made between natural settings and those m odified by man when determining rainfall thresholds for predictive pur poses. In recently urbanized mountainous environments, the thresholds used to assess landslide hazards should not be weighted too heavily on old historical records of precipitation and associated mass movements . Instead, more weight ought to be given to the period following the o ccurrence of any major anthropogenic and natural (e.g. high-magnitude earthquake) modification of slope setting.