«La Fana de Genestaza» is an active mountain torrent representative of these kind of systems in the Cantabrian Mountains. As the field evidences show, the availability of non consolidated material in the catchment area is due to rockfall processes as well as to small landslides. Although water transport processes are prevailing, sporadic discharges of debris-flow take place in the drainage channel. This process is controlled not only by the rainfall regime, but also by the volume of available material in the catchment area. The field evidences suggest a relatively high frequency for the occurrence of this kind of episodes