Sediment dynamics in tropical mountain regions : influence of anthropogenic disturbances on sediment transfer mechanisms

The aim of this thesis was to improve the understanding of sediment dynamics in tropical mountain regions by analysing the influence of anthropogenic disturbances on sediment transfer mechanisms. The main objectives were (i): to determine the influence of landslides on sediment production, transport and delivery to the river network, (ii) to identify and assess the impact of land cover changes on landslide occurrence and (iii) to evaluate the extent to which land cover dynamics affect landslide area-frequency distributions and landslide-induced erosion. This study quantitatively confirms that more than fifty percent of the sediment delivered by the hillslopes to the streams in the Western Cordillera is initially mobilised by landslides. It also shows that landslide controlling factors vary through time and that topographical factors alone cannot explain the changing landslide patterns. Human disturbances significantly alter the landslide frequency-area distributions, particularly for smaller landslides. When analysing the geomorphic work realised by landslides in different environments, it becomes clear that the majority of landslide-induced sediment is coming from anthropogenic environments. However, this thesis shows that isolating human-induced processes from natural processes is not straightforward and that human impact on the geomorphic process rates may vary according to the spatial and temporal scale of study.(SC - Sciences) -- UCL, 201