Some aspects of the initiation of debris avalanches in the Campania Region: The role of morphological slope discontinuities and the development of failure

In May 1998, a prolonged period of rainfall caused disastrous landslides in the Sarno–Quindici area (Campania, SouthernItaly). The landslides initiated as small debris slides, and developed into debris avalanches and debris flows involving theshallow pyroclastic deposits that lie on the steep, vegetated slopes of this area. In view of the potential for such events tooccur again in this area, an understanding of the initial failure mechanism is crucial if assessments are to be made of thehazard levels.In this paper, the results of detailed surveys of the morphological characteristics of the source areas are presented. Statisticalanalyses and parametrical relationships have been performed on key parameters, demonstrating that the initial failures wereassociated with the presence of morphological discontinuities, such as limestone scarps and road cuts. Notably, the presence ofman-made cuts appears to have been responsible for about the 60% of the initial debris slides. Morphometric analysis hasshown that the debris avalanches are characterised by a typical triangular shape. Statistical analyses have been used to try torelate the apex angles to relevant geomorphological parameters. Allowing for differences in local morphology the findings showsome significant correlation.