Debris flow magnitude in the Alps: data collection and analysis

The estimation of debris flow magnitude is essential for the assessment of debris flow hazard. Historical data are an important basis for evaluating magnitude and frequency of debris flows in a given geographical region. Data on debris flow magnitude concerning 130 basins of the Eastern ltalian Alps have been collected from scientific and technical journals, technical reports and historical documents gathered from local archives and through field surveys carried out in the last few years. The analysis of collected data includes various approaches. Regression techniques were used to correlate debris flow magnitude to morphometric parameters and to geological characteristics of the basins. A comparison of historical magnitudes with geomorphic field estimations carried out in recent years is presented and the relations between debris flow magnitude and frequency for a few selected cases are analysed. Some proposals about the possible combined use of considered techniques are then suggested.