GIS-based modelling of glacial sediment balance

Abstract

In view of ongoing atmospheric warming, there is concern as to whether retreating glaciers uncover a rocky or sedimentary bed. Sedimentary beds are abundant in high-mountain areas and represent, if exposed, a severe hazard potential for outbursts of periglacial lakes or debris flows. Furthermore, knowledge about glacier sediment balance is needed when dealing with climate sensitivity of recent and historical glaciers. The main factors influencing sediment balance of a glacierised mountain catchment have been organised into an index (Ies) of glacier erosion and sedimentation, which distinguishes between glaciers eroding into bedrock and those building up thick sedimentary beds. GIS-based methods were developed to extract the needed Ies-parameters from Digital Elevation Models (DEM), digitised glacier outlines and central flowlines. These methods were automated and tested on 84 Swiss Alpine glaciers. The results were validated through comparisons with forefield classifications and manually derived index results. The comparison with classified forefields confirms that the index allows for a rough assessment of the glacial sediment balance. In order to improve the predictability of glacier-bed characteristics, a better understanding of the periglacial debris production is necessary. However, the high overall accuracy of the comparison with the manual glacier-by-glacier investigation shows the potential of using GIS-based modelling with DEM in geomorphodynamics.