The paper describes the results of research in the Upper Dades Valley in the High Atlas Mountains in Morocco. The purpose of the research was to identify the impact of river channels changes, fluvial accumulation nad erosion on human activity. Fieldwork and maps were used to characterize the structure of the Dades river channel and the intensity of present-day fluvial processes. Research data show that the Upper Dades Valley is shaped primarily by short but frequent and intense hydrometeorological events. The structure of the Dades river channel indicates a complex functionality. Tributary episodic riviers and gorges sections supply most of the weathering material. Narrow sections of Dades channel serve for material as transfer zones, while deposition occurs across broader areas. Research has shown that extreme fluvial processes occurring in semi-arid mountains result in fast river chanels changes and accelerated deposition of weathering material across valley floors, which usually leads to limits on the development of agriculture in such areas.