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1 Department of Earth Sciences Cambridge, UK 2 GR - Géosciences Rennes

Abstract : We have performed a series of experiments to investigate the relationship between channel geometry and tectonic forcing in steady state landscapes at various uplift rates. The experimental setup consists of uniformly uplifted silica paste eroded by artificial rainfall. In this setup, erosional landscapes evolve by growth and amalgamation of incisions, which organize into a drainage network whose dynamics are a function of the interaction between vertical channel cutting, hillslope erosion, and sediment transport. High-precision 0.5 mm pixel size digital elevation models were constructed using a stereogrammetric camera system. From this data, channel bed slope was found to be independent of discharge and position on the experimental surface and to increase linearly with uplift rate. Geometric parameters of the flow, such as channel width or depth, could not be observed directly during the experiments. Using laminar flow equations for the mean flow velocity, these parameters were back calculated, and relationships to the imposed substrate uplift rate were derived. Channel width, cross-sectional area, and wetted perimeter decrease with increasing uplift rate to a limit value, hydraulic radius and flow depth increase slightly, and flow velocity increases approximately linearly with increasing uplift rate. These results are qualitatively consistent with recent field surveys and highlight the importance of channel width and slope variations in accommodating channel response to variable rock uplift rates.

Keywords : tectonic forcing channel morphology experimental geomorphology





Autor: Jens Turowski - Dimitri Lague - Alain Crave - Niels Hovius -

Fuente: https://hal.archives-ouvertes.fr/



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