| Summary: | National audience Over the last decades, the socio-ecosystem of Umiujaq has encountered drastic changes regarding the climatic and anthropogenic impacts. Permafrost degradation triggers the transfer of water and suspended sediments towards the Umiujaq River. Aerial photo and satellite image interpretations were used to find out the main characteristics of environmental changes on the entire watershed. During the last year, we quantified the landform evolutions along the river, and tracked bank and slope instabilities that connect to the river. Despite of a global low lateral mobility, the course and flow of the Umiujaq River evolve according to the capture of thermokarst pools that develop on its banks. Shrub development in the valley and beaver dams are also factors in modifying river processes. Fieldwork focused on a landslide deposit corresponding to a recurrent dynamic, that impacts the river morphology. Sampling was carried out in the deposits and in the source area, to contribute to the contaminant documentation of the area; trees sampling was collected to lead dendrochronologic analyses that document the study landslide multi-year dynamic. Two cameras were also installed to document (i) annual flow variation and (ii) the sediment interactions between the landslide and the river. In a context of climate warming, such slope processes and subsequent sediment sources are likely to increase in number. It is therefore important to understand the interaction of these compartments (slopes, watercourses, etc.) in order to understand and anticipate future changes and trajectories. Au cours des dernières décennies, le socio-écosystème d'Umiujaq a connu des changements drastiques en ce qui concerne les impacts climatiques et anthropogéniques. La dégradation du pergélisol déclenche le transfert d'eau et de sédiments en suspension vers la rivière Umiujaq. Des interprétations de photos aériennes et d'images satellites ont été utilisées pour déterminer les principales caractéristiques des changements environnementaux ...
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