Morphodynamic simulation of sediment deposition patterns on a recently stripped bedrock anastomosed channel

Milan, David; Heritage, George; Entwistle, Neil; Tooth, Stephen

Abstract

Some mixed bedrock-alluvial dryland rivers are known to undergo cycles of alluvial building during low flow periods, punctuated by stripping events during rare high magnitude flows. We focus on the Olifants River, Kruger National Park, South Africa, and present 2D morphodynamic simulations of hydraulics and sediment deposition patterns over an exposed bedrock anastomosed pavement. We examine the assumptions underlying a previous conceptual model, namely that sedimentation occurs preferentially on bedrock highs. Our modelling results and local field observations in fact show that sediment thicknesses are greater over bedrock lows, suggesting these are the key loci for deposition, barform initiation and island building. During peak flows, velocities in the topographic lows tend to be lower than in intermediate topographic areas. It is likely that intermediate topographic areas supply sediment to the topographic lows at this flow stage, which is then deposited in the lows on the falling limb of the hydrograph as velocities reduce. Subsequent vegetation establishment on deposits in the topographic lows is likely to play a key role in additional sedimentation and vegetation succession, both through increasing the cohesive strength of alluvial units and by capturing new sediments and propagules.

Citation

Milan, D., Heritage, G., Entwistle, N., & Tooth, S. Morphodynamic simulation of sediment deposition patterns on a recently stripped bedrock anastomosed channel. Presented at IAHS Scientific Assembly 2017, Port Elizabeth, South Africa

• Presentation Conference Type: Conference Paper (published)
• Conference Name: IAHS Scientific Assembly 2017
• Acceptance Date: Aug 16, 2017
• Online Publication Date: Apr 16, 2018
• Publication Date: Apr 16, 2018
• Deposit Date: Sep 18, 2017
• Publicly Available Date: Nov 22, 2018
• Journal: Proceedings of the International Association of Hydrological Sciences
• Print ISSN: 2199-8981
• Publisher: Copernicus Publications
• Peer Reviewed: Peer Reviewed
• Volume: 377
• Pages: 51-56
• DOI: https://doi.org/10.5194/piahs-377-51-2018
• Keywords: LiDAR, anastomosed, dryland river, 2D Morphodynamic simulation, sediment transport
• Public URL: https://hull-repository.worktribe.com/output/454814
• Publisher URL: https://www.proc-iahs.net/377/51/2018/
• Additional Information: This is the authors' accepted manuscript of an article which has been accepted for future publication in: Proceedings of the International Association of Hydrological Sciences
• Contract Date: Sep 18, 2017