Long-term flood controls on semi-arid river form : evidence from the Sabie and Olifants rivers, eastern South Africa

Heritage, G; Tooth, S; Entwistle, NS; Milan, D

Abstract

Rivers in the Kruger National Park, eastern South Africa, are characterised by bedrock-influenced ‘macrochannels’ containing variable alluvial thicknesses and riparian vegetation assemblages. Evidence from the Sabie and Olifants rivers suggests that flows up to moderate floods (<3500 m3 s-1) tend to result in net alluviation, with sediments gradually covering the underlying bedrock. More extreme floods strip alluvium and erode bedrock, effectively exerting the primary control over long-term river morphologic development. On the Olifants River, post-flood aerial LIDAR imagery reveals that the 2012 extreme flood (~14000 m3 s-1) resulted in extensive stripping of stored alluvial sediment, exposing and eroding the underlying weathered bedrock. On the Sabie River, preliminary optically stimulated luminescence ages for remnant alluvium are all less than 1000 years, highlighting typical timescales of sediment storage. Together, these results suggest that while periods of general alluviation occur on these systems, long-term river development results from extreme flood-generated bedrock erosion.

Citation

Heritage, G., Tooth, S., Entwistle, N., & Milan, D. (2015). Long-term flood controls on semi-arid river form : evidence from the Sabie and Olifants rivers, eastern South Africa. Proceedings of the International Association of Hydrological Sciences, 367, 141-146. https://doi.org/10.5194/piahs-367-141-2015

• Journal Article Type: Article
• Publication Date: Mar 3, 2015
• Deposit Date: Jan 19, 2015
• Publicly Available Date: Apr 5, 2016
• Journal: Proceedings of the International Association of Hydrological Sciences
• Print ISSN: 2199-8981
• Publisher: Copernicus Publications
• Peer Reviewed: Peer Reviewed
• Volume: 367
• Pages: 141-146
• DOI: https://doi.org/10.5194/piahs-367-141-2015
• Publisher URL: http://dx.doi.org/10.5194/piahs-367-141-2015
• Related Public URLs: http://www.proceedings-international-association-of-hydrological-sciences.net/