Erosion prediction in ungauged glacierized basins

Methods to estimate sediment yields in ungauged glacierized areas are discussed and the sediment load in ungauged parts of the Svartisen hydropower scheme in northern Norway is estimated as an example. Long-term measurements of sediment yields of various glaciers in Norway revealed that erosion rates to a large extent are controlled by bedrock geology, glacial variables and large scale morphology of each individual glacier. Measurements of bed load G(b) and suspended load G(s) of two glaciers gave a relation G(b) = k G(s). Long-term values of the parameter k were found to vary between 0.67 and 1.0. The existence of such a relationship is due to the fact that suspended load is derived from abrasion and crushing of the coarser glacially quarried material. In the Svartisen hydropower scheme, direct measurements of sediment fluxes were carried out at selected locations. The sediment yields of the remaining ungauged catchments were then estimated from an evaluation of each individual glacier and the underlying bedrock. This gave as a result a suspended load and a bed load of 7100 t year(-1) and 4760 t year(-1), respectively, for the eastern tunnel, and of 20 300 and 13 600 t year(-1), respectively, for the southern tunnel complex. The amount of sediment delivered by the glaciers draining directly into the reservoir was calculated as 103 000 t year(-1), using sedimentation rates in dated sediment cores from the reservoir bed. The sediment yield of other glacier areas is discussed.