Debris flow relationships in the Central Spanish Pyrenees

Abstract

Debris flows represent the most active geomorphic risk in mountainous areas, affecting infrastructures, human settlements and touristic resorts (Takahashi et al., 1981). For this reason, much effort has been put in assessing where debris flows occur and ranking the factors that trigger them, but also in defining two essential parameters in establishing debris flow hazards: what is the distance travelled by debris flows (especially the runout distance), and what is the volume of material carried out by debris flows, as well as the relationships between different debris flow parameters. This information is a very relevant input for debris flow modelling and to predict the areas most probably affected by future debris flows. In this report the characteristics of debris flow parameters are studied, in order to establish formulas allowing the calculation of debris flow transport distance and sediment volume delivered to the streams. Parallel effort has been put to predict the occurrence of debris flows in the hillslopes. The results from this report are the base to assess the debris flow hazard for infrastructures and settlements, as well as for arriving to the fluvial network and deliver large volumes of sediment.