Sediment Transport in Glacial Meltwater Streams
Glacierized areas in Norway are being considered for future hydro-electric power production due to favorable hydrologic conditions; these include high specific water yield at high altitudes and at relatively short distances from tide water. However, technical problems can be expected in utilization of sedimentladen water, particularly in reservoirs and in the turbines. A study program of sediment transport and deposition was therefore initiated, and some of the major results are given in this paper.
Suspended-sediment transport was determined at five selected glaciers by frequent water sampling, at least five samples being taken daily. Sediment concentration ranged from tens of milligrams per liter to several grams per liter, and rapid variations were experienced, particularly in periods of increasing water discharge. No simple correlation was found between water discharge and suspended sediment load but, in general, years of low total water discharge gave less sediment transport than years of high total discharge.
Bed load was determined at one glacier (Nigardsbreen outlet glacier from the Jostedalsbreen Ice Cap) by trapping all coarse material in a large, strong fence built across the river. The bed load accounted for 30 to 50 percent of the total transport of solid matter, as measured close to the glacier terminus. The rate of sedimentation in a natural lake close to a glacier was established both as a difference between sediment input and output and by a study of older deposits on the lake bottom. Annual layers (varves) were easily recognized and studies were made of their grain size and mineral composition. “Winter" layers had finer grains, more mica and less quartz than "summer” layers. A great part (70 percent or more) of the suspended-sediment input into the lake settled on its bottom, and the remainder that left the lake consisted mainly of the finest grain size fractions.
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Glaciofluvial and Glaciolacustrine Sedimentation
This publication is the outgrowth of a symposium on Glacial Sedimentology that was held in Buffalo, New York, March 1972. The great interest generated in glacial phenomena during the nineteenth century had important implications and repercussions for the infant field of sedimentology. It provided its fair share of the background stimulus necessary to establish sedimentology as a separate branch of the earth sciences in the twentieth century. The time for reciprocity is now at hand; feedback from the expertise gained in the burgeoning field of sedimentology can greatly help the Quaternary specialist solve particular field problems. The last decade has witnessed a growing interest in the sedimentology of the Quaternary, and it seems appropriate now to summarize progress in the study of stratified drift, to present results of some recent studies, and to focus attention on avenues of research that should be explored in the near future.