Preprints
https://doi.org/10.5194/hess-2023-267
https://doi.org/10.5194/hess-2023-267
02 Jan 2024
 | 02 Jan 2024
Status: a revised version of 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 Paster, Peter Flödl, Anton Neureiter, Gernot Weyss, Berhnard Hynek, Ulrich Pulg, Rannveig Øvrevik Skoglund, Helmut Habersack, and Christoph Hauer

Abstract. Global warming and glacier retreat are affecting the morphodynamics of proglacial rivers. In response to changing hydrology, the altered hydraulics will significantly impact future glacifluvial erosion and proglacial channel development. This study analyses a proglacial channel evolution process at the foreland of Austria’s biggest glacier Pasterze, by predicted runoff until 2050 based on a glacio-hydrological model. A high-resolution digital elevation model was created by an unmanned aerial vehicle, sediment 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< 79 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> 179 mm). Furthermore, already reoccurring exposed non-fluvial grain sizes combined with decreasing flow competence in the long term indicate erosion-resistant pavement layer formation disconnecting the subsurface sediments for glacifluvial reworking (vertical landform decoupling). The presented study shows that subsystems exhibiting pavement layer formation by grains exceeding the predicted transport capacity supported by non-fluvial sediments 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.

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Michael Paster, Peter Flödl, Anton Neureiter, Gernot Weyss, Berhnard Hynek, Ulrich Pulg, Rannveig Øvrevik Skoglund, Helmut Habersack, and Christoph Hauer

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2023-267', Anonymous Referee #1, 17 Jan 2024
  • RC2: 'Comment on hess-2023-267', Anonymous Referee #2, 21 Apr 2024
Michael Paster, Peter Flödl, Anton Neureiter, Gernot Weyss, Berhnard Hynek, Ulrich Pulg, Rannveig Øvrevik Skoglund, Helmut Habersack, and Christoph Hauer
Michael Paster, Peter Flödl, Anton Neureiter, Gernot Weyss, Berhnard Hynek, Ulrich Pulg, Rannveig Øvrevik Skoglund, Helmut Habersack, and Christoph Hauer

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Short summary
Triggered by global warming, glacier melt is repeatedly reaching peak values year by year. This development leads to a continuous enlargement of glacier forelands, accompanied by increasing sediment availability and a change in meltwater runoff behavior. The study describes an essential development step of proglacial channel evolution using river engineering methods. This is relevant to adequately define glacifluvial processes and downstream sediment yields in these transitioning landscapes.