Val Pola rock avalanche of July 28, 1987, in Valtellina (Central Italian Alps)
Published:January 01, 2002
Mario Govi, Giovanni Gullà, Pier Giorgio Nicoletti, 2002. "Val Pola rock avalanche of July 28, 1987, in Valtellina (Central Italian Alps)", Catastrophic Landslides, Stephen G. Evans, Jerome V. Degraff
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The Val Pola rock avalanche began when a sagging slope failed due to toe unloading. The mass then plunged down into a narrow valley from a considerable height, crossed the valley, parted, rebounded, and, in part, ran back up to the source slope. Seven men were killed in this stage. The destabilization of this 34 × 106 m3 rock mass (mostly diorite) was triggered by heavy rainfalls that caused shallow landslides on the Val Pola sides and debris flows along the Val Pola thalweg. These processes resulted in a 35 m deepening of the canyon along the toe of the sagging slope. The morphology of the accumulation is mostly characterized by frequent, aligned hummocks and depressions, by reverse runup ridges, and by a narrow, 900-m-long, tongue-like downstream extension. The interaction between the moving mass and local morphology resulted in a relatively moderate runout and an unusually high degree of spreading. The north arm of the rock avalanche displaced the water of a preexisting landslide-dammed lake, generating a wave that killed 22 people more than 2 km upstream. A new and greater lake was formed as a consequence of the event. The systematic identification of sagging slopes and the establishment of reference geotechnical models are suggested for hazard prevention and emergency management.
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>This volume documents further advances in our knowledge of catastrophic landslides since the pioneering compilations of the late 1970s by Barry Voight. It provides a worldwide survey of catastrophic landslide events written by leading authorities. Catastrophic Landslides begins by drawing upon South America to dramatically illustrate the impact of these phenomena on human populations. The occurrence of catastrophic landslides, including site-specific insights, is shown through six events of the past 20 years. Several other chapters focus on the mechanisms involved with catastrophic landsides both in relation to geologic factors in a particular geographic area as well as to specific geologic processes.