Preprints
https://doi.org/10.5194/hess-2022-347
https://doi.org/10.5194/hess-2022-347
 
13 Dec 2022
13 Dec 2022
Status: this preprint is currently under review for the journal HESS.

Channel evolution processes in a diamictic glacier foreland. Implications on downstream sediment supply: Case study Pasterze/Austria

Michael Paster1, Peter Flödl1, Anton Neureiter2, Gernot Weyss2, Bernhard Hynek2, Ulrich Pulg3, Rannveig Øvrevik Skoglund4, Helmut Habersack1, and Christoph Hauer1 Michael Paster et al.
  • 1CD-Laboratory for Sediment research and management, Institute of Hydraulic Engineering and River Research, Department of Water, Atmosphere and Environment, University of Natural Resources and Life Sciences Vienna, Muthgasse 107, 1190 Vienna, Austria
  • 2Department for Climate Research, Central Institute for Meteorology and Geodynamics, Hohe Warte 38, 1190 Vienna, Austria
  • 3UNI Research Miljø, Laboratorium for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5006 Bergen, Norway
  • 4University of Bergen, Fosswinckelsgt. 6, 5006, Bergen, Norway

Abstract. Global warming and glacier retreat are affecting the morphodynamics of proglacial rivers. In response to changing hydrology, their altered hydraulics will significantly impact future glacifluvial erosion and proglacial channel development. This study analysis proglacial channel evolution processes at the foreland of Austria’s biggest glacier Pasterze by predicted runoff until 2050. A high-resolution digital elevation model was created by an unmanned aerial vehicle, channel bathymetry was sampled, a one-dimensional hydrodynamic-numerical model was generated, and bedload transport formulas were used to calculate the predicted transport capacity of the proglacial river. Due to the fine sediment composition near the glacier terminus (d50 < 49.6 mm), the calculation results underline the process of headward erosion in the still unaffected, recently deglaciated river section. In contrast, an armor layer is already partly established by the coarse grain size distribution in the already incised river section (d50 > 201 mm). Furthermore, already occurring exposed non-fluvial grain sizes combined with decreasing flow competence in the long term are indicators for erosion-resistant pavement layer formation and landform decoupling in the vertical direction. The presented study clearly shows that subsystems of ‘developed channels’ exhibiting pavement formation of non-fluvial deposits are found at the investigated glacier foreland. Thus, an extension accompanied by a refinement of the fluvial system in the sediment cascade approach was developed as a central result.

Michael Paster et al.

Status: open (until 22 Feb 2023)

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Michael Paster et al.

Michael Paster et al.

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Short summary
Glaciers experienced record-breaking melting rates in recent years. This development leads to a continuous enlargement of glacier forelands, accompanied by increasing sediment availability and altered meltwater runoff behavior. This study describes the final development step of the gradual meltwater channel evolution using river engineering techniques. This is relevant to adequately define high alpine fluvial processes and sediment yields in these transitional landscapes.