Evaluation of hydrogeological hazard on alluvial fans

Alluvial fans represent a broad morphological category including elements built-up by very different phenomena and processes. Alluvial fans are also historically preferred building sites, in alpine and pre-alpine areas, even if frequently characterised by intense and extensive flooding. Since the early sixties researchers tried to characterise alluvial fans by measuring and computing morphological parameters that could be related to their relative flood hazard and risk. This approach is used and discussed in this paper, starting from a series of data and observations collected in the Central Italian Alps within the Lombardy Region territory. Statistical techniques are used to discriminate among a sample of 97 alluvial fans, to compare and obtain semi-empirical formulas for the forecast ofthe magnitude of flooding events from morphometric parameters.