This book explores a new conceptual approach, closer to hydrology than hydraulics, which relies solely and rigorously on field data from the avalanche path studied. This approach is clarified and compared with both the deterministic and statistical approaches. The authors' past and current research implementing this approach is presented: analysis of the bulk rheology of certain avalanches, the elaboration of new conceptual models validated by comparison with field data, and a methodology for determining extreme events by extrapolating the knowledge garnered from past events