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| Titel |
Fluvial response to environmental perturbations: a perspective from physical experiments |
| VerfasserIn |
Sara Savi, Stefanie Tofelde, Andrew Wickert, Taylor Schildgen, Chris Paola, Manfred Strecker |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124849
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| Publikation (Nr.) |
 EGU/EGU2016-4343.pdf |
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| Zusammenfassung |
| Fluvial terraces and alluvial fans that are perched above the modern base level testify to
environmental conditions that were different from today. Sedimentological studies combined
with chronological constraints can be used to reconstruct the evolution of these landforms in
the context of past changes in regional to global forcing. Despite the improvements in the
most commonly used dating techniques (e.g. cosmogenic nuclides, 14C, and OSL), field
data from fluvial and alluvial archives often represent only a brief glimpse into the
evolution of that particular landscape. As such, the challenge of interpreting landscape
development and its relationship to external forcing in the remaining time gaps is often
unclear.
To gain more insight, we performed physical experiments to test how a fluvial system
responds to changes in the boundary conditions. This approach allows us to continuously
record the evolution of the fluvial system and to observe, step by step, the response of the
fluvial system and the development of the landscape. Additionally, we can directly link
the geomorphic modifications to a specific environmental perturbation. Starting
with a simple model and a single channel, we changed the amount of discharge
(Qw) and sediment supply (Qs) in the system. The most prominent response results
from a sudden increase in water discharge. In general, changes in the Qs/Qw ratio
control the fluvial morphology (particularly the height/width ratio), the channel’s
profile, the dynamics of the river, and its ability to modify the surrounding landscape.
Responses get more complex with the introduction of a lateral tributary, which
changes the dynamics of the main stem and creates feed-back mechanisms between
the two systems. For example, a change in the main stem can influence the fluvial
morphology and the steepness of the tributary (even with no perturbations in the tributary)
and vice-versa, illustrating the potential for non-unique interpretations of fluvial
landforms.
Our preliminary results indicate that any modification in sediment supply or water
discharge has the ability to leave distinct imprints on the landscape and suggest
that these signals, in turn, may be used to infer the direction of the changes that
occurred in the past. As such, our experiments provide information for a more robust
and reliable interpretation of sedimentary archives, furnishing insights into how
geomorphological features could be related to specific environmental perturbations. |
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