DEBRIS-FLOW MAGNITUDE-FREQUENCY RELATIONSHIPS FOR MOUNTAINOUS REGIONSOF CENTRAL AND NORTHWEST EUROPE

Debris-flow activity within a given area can be defined in terms of ma gnitude and frequency. When for such an area ranges of event magnitude s can be related to the corresponding frequencies, the regional charac teristics of debris-flow activity will be obtained. From the viewpoint of hazard assessment this magnitude-frequency characteristic is an es sential element of the debris-flow process. For larger areas, (supra)r egional comparison may also be undertaken on this basis. However, the data available often specify magnitude insufficiently. For the present study, published data specifying both magnitude and frequency (a very limited amount) were used for the Alps, the Tatra Mountains, Scotland , Norway, and Swedish Lapland in addition to material for the French A lps from the author's research. Activity levels within Northwest Europ ean mountains were found to be lower than in the Alps or the Tatras. P ossible explanations are discussed, in which precipitation patterns an d debris availability play a prominent part. However, the general conc lusion has to be that firm statements about the causes of observed dif ferences in magnitude-frequency patterns cannot yet be given.