Preprints
https://doi.org/10.5194/esurf-2021-90
https://doi.org/10.5194/esurf-2021-90

  30 Nov 2021

30 Nov 2021

Review status: this preprint is currently under review for the journal ESurf.

Spatio-temporal variability and controlling factors for postglacial erosion dynamics in the Dora Baltea catchment (western Italian Alps)

Elena Serra1,2, Pierre Gaston Valla3,1,2, Romain Delunel4, Natacha Gribenski1,2, Marcus Christl5, and Naki Akçar1 Elena Serra et al.
  • 1Institute of Geological Sciences, University of Bern, Bern, 3012, Switzerland
  • 2Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland
  • 3University Grenoble Alps, University Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, Grenoble, 38000, France
  • 4Université Lumière Lyon 2, CNRS, UMR 5600 EVS, F-69635, France
  • 5Laboratory of Ion Beam Physics, Swiss Federal Institute of Technology Zurich (ETHZ), Zurich, 8093, Switzerland

Abstract. Disentangling the influence of bedrock erodibility from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial/temporal scales involved. The Dora Baltea catchment (western Italian Alps) appears the ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major litho-tectonic units of the western Alps, whereas this region has experienced homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new 10Be-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rate results vary between 0.2 and 0.9 mm/yr, consistent with values obtained across the European Alps by previous studies. Spatial variability in denudation rates was statistically compared with topographic, environmental and geologic metrics. 10Be-derived denudation records do not correlate with the distribution of modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock erodibility (litho-tectonic origin) and glacial overprint, has the main influence on denudation rates. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support steep slopes and high relief and thus favour intense glacial/periglacial processes and recurring rock fall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low 10Be concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.

Elena Serra et al.

Status: open (until 22 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-90', Anonymous Referee #1, 21 Dec 2021 reply
  • RC2: 'Comment on esurf-2021-90', Anonymous Referee #2, 14 Jan 2022 reply

Elena Serra et al.

Elena Serra et al.

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Short summary
Alpine landscapes are transformed by several erosion processes. 10Be concentrations measured in river sediments at the outlet of a basin represent a powerful tool to quantify how fast the catchment erodes. We measured erosion rates within the Dora Baltea catchments (western Italian Alps). Our results show that erosion is governed by topography, bedrock resistance and glacial imprint: hard lithologies support high reliefs affected by glacial/periglacial processes and recurring rock fall events.