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| Titel |
Sediment yield from a large alpine glacier over one season |
| VerfasserIn |
Ian Delaney, Mauro Werder, Andreas Bauder |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250142043
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| Publikation (Nr.) |
 EGU/EGU2017-5617.pdf |
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| Zusammenfassung |
| Hydropower operators in the Swiss Alps have noted increased reservoir sedimentation rates
in the last decade. This material either originates from erodible periglacial areas, no longer
stabilized by ice, or from subglacial environments, where it is transported by pressurized
melt-water. In order to forecast sediment production on subyearly timescales as
glaciers retreat and hydrological conditions evolve, the processes that transport
subglacial sediment must be further described and integrated into numerical models. To
determine and model these processes we have examined Gornergletscher in the Valais
Alps.
By measuring suspended sediment expelled from the glacier, along with data from
sediment traps used by the hydropower company to estimate bedload transport, we have
quantified the glacier’s sediment output during the 2016 melt season. The highest
concentrations of suspended sediment occurred in late May and early June 2016
during drainage of an ice marginal lake. However, sediment evacuated during this
two week period is not as high as during other parts of the season, at just above
5% the season total. This indicates that although an undeveloped drainage system
can indeed erode considerable amounts sediment, the flux is heavily dependent on
discharge and thus much sediment is available for transport below the glacier. In an
effort to apply the observations at Gornergletscher to a broader context, a simple
model has been devised and calibrated with the above mentioned data. Using the
Darcy-Weisbach equation for pressurized flow through a pipe, we constrain the
propensity for subglacial sediment transport. With inputs of hydraulic gradient,
discharge and conduit shape, we determine shear stress of water flowing through the
glacier’s hydraulic system on subglacial sediments. This enables us to reconcile the
competing process of decreased (increased) hydraulic gradient (discharge) which
decrease (increase) the ability of water to erode sediment as conditions in glacierized
catchments evolve. This model requires inputs of discharge and glacier topography and
thickness, thus making it applicable to other glaciers with these datasets available. |
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