3-D architecture, depositional patterns and climate triggered sediment fluxes of an alpine alluvial fan (Samedan, Switzerland)

Hornung, Jens; Pflanz, Dorthe; Hechler, A.; Beer, Alexander R.; Hinderer, Matthias; Maisch, Max; Bieg, U.

doi:10.1016/j.geomorph.2009.09.001

Cited by 42 publications

(43 citation statements)

References 9 publications

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“…Glacier inheritance influences sediment production and transport as demonstrated by a strong spatial association between sediment yield and past and current glacial cover (Hinderer et al, 2013;Delunel et al, 2014). Almost continuous temperature-driven glacier recession in the European Alps since the late 19th century (Paul et al, 2004Haeberli et al, 2007) has maintained large parts of the landscape in early stages of the paraglacial phase, where unstable or metastable sediment sources (Ballantyne, 2002;Hornung et al, 2010) can maintain high sediment supply rates. Anthropogenic impacts on sediment yields are more recent, and on a global scale largely related to land-cover change through intensified agriculture and the trapping of sediment in reservoirs (e.g.…”

Section: Introductionmentioning

confidence: 99%

Temperature signal in suspended sediment export from an Alpine catchment

Costa

Molnár

Stütenbecker³

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Suspended sediment export from large Alpine catchments ( > 1000 km 2 ) over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation-deactivation of different sediment sources (proglacial areas, hillslopes, etc.), transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation). Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhône River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity), and the activation of different potential sources of fine sediment (sediment supply) in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degreeday model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment concentration through hillslope erosion by rainfall on snow-free surfaces, and increased meltwater production on snow-free glacier surfaces. Despite the rise in air temperature, changes in mean discharge in the mid-1980s were not statistically significant, and their interpretation is complicated by hydropower reservoir management and the flushing operations at intakes. Overall, the results show that to explain changes in suspended sediment transport from large Alpine catchments it is necessary to include an understanding of the multitude of sediment sources involved together with the hydroclimatic conditioning of their activation (e.g. changes in precipitation, runoff, air temperature). In addition, this study points out that climate signals in suspended sediment dynamics may be visible even in highly regulated and human-impacted systems. This is particularly relevant for quantifying climate change and hydropower impacts on streamflow and sediment budgets in Alpine catchments.

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Section: Introductionmentioning

confidence: 99%

Temperature signal in suspended sediment export from an Alpine catchment

Costa

Molnár

Stütenbecker³

et al. 2018

Hydrol. Earth Syst. Sci.

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“…Deposition of sediment by repeated flows results in the construction of debris-flow fans that can potentially record information on past flow size, timing, composition, and depositional pattern (Schumm et al, 1987;Harvey, 2011). Such fans are therefore a potentially powerful archive of debris-flow processes (e.g., Whipple and Dunne, 1992;Dühnforth et al, 2007;d'Arcy et al, 2015;de Haas et al, 2015ade Haas et al, , 2015b, hazard (e.g., Hubert and Filipov, 1989;Helsen et al, 2002;Stoffel et al, 2008a;Arattano et al, 2010;de Scally et al, 2010), and sediment supply (e.g., McDonald et al, 2003;Dühnforth et al, 2008;Hornung et al, 2010;Savi et al, 2014). Reading that archive, however, and extracting quantitative information about past debris flows, requires that we understand the pattern and timing of debris flow deposition on fans so that the evolution of the fan can be reconstructed.…”

Section: Introductionmentioning

confidence: 99%

Quantitative reconstruction of late Holocene surface evolution on an alpine debris-flow fan

et al. 2016

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Citation for published item:h¤ urhD F nd hensmoreD eFvF nd svyEyhsD F nd osserD xFtF nd uoerD pF nd hluneggerD pF nd werdellD fF nd el(movD F @PHITA 9untittive reonstrution of lte roloene surfe evolution on n lpine derisE)ow fnF9D qeomorphologyFD PUS F ppF RTESUF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Cl exposure dating of debris-flow deposits on the fan to constrain the temporal evolution of the sediment routing system in the catchment and on the fan during the past 3200 years. We show that the fan surface preserves a set of debris-flow lobes that were predominantly deposited after the occurrence of a large rock avalanche near the fan apex at about 3200 years ago. This rock avalanche shifted the apex of the fan and impounded sediment within the Illgraben catchment. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTSubsequent evolution of the fan surface has been governed by both lateral and radial shifts in the A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTactive depositional lobe, revealed by the cosmogenic radionuclide dates and by cross-cutting geometrical relationships on the fan surface. This pattern of frequent avulsion and fan surface occupation provides field-scale evidence of the type of large-scale compensatory behavior observed in experimental sediment routing systems.

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“…During the transition from the Younger Dryas to the early Holocene (12–9.3 ka), this same catchment experienced high sedimentation rates and debris‐fan growth at the catchment mouth. Similarly, sediment flux estimates on an alluvial fan in Switzerland indicate the importance of climatic controls on sedimentation rates, and document a decline in total sediment flux during the Holocene (Hornung et al ., ). The rate of coarse debris production in the Colorado Rockies may have been up to two orders of magnitude greater during the late Pleistocene and Neoglacial periods (Dethier et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Patterns of debris flow initiation and periglacial sediment sourcing in the Colorado Front Range

Patton

Rathburn

Bilderback

et al. 2018

Earth Surf Processes Landf

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During an extreme storm in the Colorado Front Range in September 2013, 11 debris flows initiated at high elevations in Rocky Mountain National Park. We characterized these debris flows to determine controls on their initiation and found that eight of the 11 initiated in areas of convergent topography, and eight initiated at elevations > 2800 m. The high proportion of debris flows in areas of convergent topography emphasizes the importance of local topographic control on initiation. Debris flows at high elevations in the Front Range are atypical; this event broadens our understanding of debris flow regimes in the Front Range. Survey data (scarp dimensions, transport distance) suggest that transport is influenced by downslope processes rather than characteristics of the initiation site. At one site with evidence of multiple debris flows sourced from the same colluvial hollow, we obtained relative ages of debris flow deposits through geomorphic mapping and fan stratigraphy. We used radiocarbon and beryllium‐10 (10Be) analysis to age stratigraphic deposits and debris flow levees. Radiocarbon ages (n = 6) were highly variable and were interpreted to reflect secondary hillslope processes rather than debris flow ages. Large ranges in cosmogenic exposure age and anomalously old samples indicate that sampled boulders (n = 14) contained inherited 10Be concentrations. Beryllium‐10 concentrations were likely acquired as exposed bedrock surfaces or during intermediate storage in the colluvial hollow. We suggest that 10Be inheritance limits the utility of cosmogenic exposure dating of debris flows with short transport distances (10−1 to 101 km). Despite these limitations, we documented field evidence for four to seven debris flows in the last 75 ka, including two in the last 8 ka. Considered collectively, 10Be sample ages from all levees suggest that greatest sediment production occurred during Quaternary glacial stages due to periglacial processes. Subsequent evacuation of the colluvial hollow likely occurred during wetter periods of the mid‐Holocene. © 2018 John Wiley & Sons, Ltd.

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3-D architecture, depositional patterns and climate triggered sediment fluxes of an alpine alluvial fan (Samedan, Switzerland)

Cited by 42 publications

References 9 publications

Temperature signal in suspended sediment export from an Alpine catchment

Temperature signal in suspended sediment export from an Alpine catchment

Quantitative reconstruction of late Holocene surface evolution on an alpine debris-flow fan

Patterns of debris flow initiation and periglacial sediment sourcing in the Colorado Front Range

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