| dc.description.abstract | Colluvial fans are built up by different slope processes, which often are discussed separately, while the reality is mostly a complex system with several interlinked processes occurring in the same area. Generations of snow avalanches, debris flows, rock avalanches and rock falls have over time built up a 1.5-km2 large colluvial fan, called Gråfonnvifta, lying on top of the detachment area of several landslides and moraine.
The main goal with this study is to get a better understanding of how these different processes can influence debris flow processes and terrain development on this fan. The study area is located in the east slope of a glacially shaped valley with alpine mountains, and has a northsouth orientation in Innfjorddalen valley, Western Norway. Mean annual precipitation is about 1500 mm, and gneisses dominate the bedrock. Debris flow processes on Gråfonnvifta are present in two different systems, which differs from each other in release -, transport - and deposit area, despite the fact that they have the same source area.
The methods used include fieldwork and quaternary mapping of Gråfonnvifta, done by digital photogrammetry in ArcGIS, as well as analysis of available meteorological data and historical debris flows events. Additional data from a meteorological station established near Gråfonnvifta have been available, as the thesis is a part of a project by NGU in cooperation with NVE. Results shows that precipitation cannot be the main cause for all earlier debris flow events. Further investigation shows that snow melt, weathering processes and geological conditions can be factors triggering and developing the two debris flows systems in different ways, and over time result in the landscape as we can see it today. | nb_NO |