FLUVIAL TRANSPORT DURING THERMALLY AND PLUVIALLY INDUCED PEAK RUNOFF EVENTS IN A GLACIER-FED MOUNTAIN CATCHMENT IN WESTERN NORWAY
Results compiled after three years of process monitoring and analysis in the glacier-fed Erdalen catchment, situated in the steep fjord-landscape of western Norway, indicate that there are significant intra- and inter-annual variations with respect to fluvial sediment transport rates and sediment yields. Three different periods with a high frequency of major discharge events can be identified over the year, with these three periods showing a significant inter-annual variability. High runoff in spring (April–June) is mainly caused by snowmelt whereas major discharge events in summer (July–August) are due to thermally caused glacier melt. In autumn (September–November), major discharge events are associated with heavy rainfall events. Autumn is the most important period with respect to fluvial sediment transport and fluvial sediment yields. Fluvial sediment transport and fluvial sediment yields in Erdalen are altogether supply-limited. The intensity of fluvial transport in autumn and over the entire year depends strongly on the number of heavy rainfall events that trigger transfers of sediments from slopes into channels via saturation overland flow with connected slope wash and debris flow events. Annual suspended sediment yields are about two times greater than annual solute yields corrected by atmospheric inputs. Suspended sediment concentrations in glacier melt water during summer and annual sediment yields in Erdalen are both lower than in many other glacierized catchments worldwide. Because of the quantitative importance of single meteorological events for fluvial sediment transport and yields, and the high intra- and inter-annual variability of sediment yields in Erdalen, process monitoring and analysis will be continued to be able to calculate more reliable annual sediment yields and denudation rates.