Complete Grain-Size Analyses on Debris-Flow Source Area in the Carrara Marble Basins, Apuane Alps, Italy

Since the first exploitation in the Roman period, marble quarrying in the Carrara Marble Basins (Northern Italy) has produced a large amount of debris which remains on the slopes as dump deposits, locally called “ravaneti”. The occurrence of debris flows sourced from ravaneti has increased dramatically in the past few years. The aim of this work is to analyse the relationship between debris-flow events and the sedimentological characteristics of relative source areas. Special sampling procedures and image analysis are used to obtain grain-size analyses over a more extensive range covering all the sediment involved in debris-flow events. Analyses in the source areas and in the deposits not affected by mobilization highlight that the silt and clay fractions, produced by the recent techniques of block cutting and grinding (directly dumped into the ravaneti), enhance debris-flow probability.