Within-Event Spatially Distributed Bedload: Linking Fluvial Sediment Transport to Morphological Change

Reenie, C.D., Williams, R. , Brasington, J., Vericat, D. and Hicks, M. (2012) Within-Event Spatially Distributed Bedload: Linking Fluvial Sediment Transport to Morphological Change. In: Hydraulic Measurements and Experimental Methods, Snowbird, UT, USA, 12-15 Aug 2012,

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Abstract

Maps of apparent bedload velocity are presented along with maps of associated channel change. Apparent bedload velocity is the bias in acoustic Doppler current profiler (aDcp) bottom track (Doppler sonar) due to near-bed particle motion (Rennie et al. 2002). The apparent bedload velocity is correlated to bedload transport (Rennie and Villard 2004), and thus serves as an indicator of local bedload transport. Spatially distributed aDcp surveys in a river reach can be used to generate maps of channel bathymetry, water velocity, bed shear stress, and apparent bedload velocity (Rennie and Church 2010). It is possible to relate the observed spatial patterns of bedload and forcing flow. In this paper, the technique is used to measure bedload flux pathways during two sequential aDcp spatial surveys conducted in a Rees River, New Zealand braid bar diffluence-confluence before and after a major flood event that inundated the entire braid plain. The aDcp surveys were complemented with terrestrial laser scans (TLS) of the bar topography. Linking aDcp bathymetry and TLS topography allowed for generation of complete digitial elevation models (DEMs) of the reach, from which morphological change between surveys were determined. Most intriguingly, the primary bedload pathway observed during the first survey resulted in sufficient deposition during the major flood event to fill and choke off an anabranch. This is perhaps the first direct field measurement of spatially distributed bedload and corresponding morphological change.

Item Type:Conference Proceedings
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Williams, Dr Richard
Authors: Reenie, C.D., Williams, R., Brasington, J., Vericat, D., and Hicks, M.
Subjects:G Geography. Anthropology. Recreation > GB Physical geography
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Geography
Copyright Holders:Copyright © 2012 The Authors
Publisher Policy:Reproduced with permission of Authors
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