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The origin and development of the Nyl River floodplain wetland, Limpopo Province, South Africa: trunk-tributary river interactions in a dryland setting

Journal Article


Abstract


  • The Nyl River floodplain wetland, one of South Africa's largest floodplain wetlands and a Ramsar site of international conservation importance, is located in an area of long-term and still active valley sediment accumulation. Creation of accommodation space for sedimentation has previously been attributed to tectonic controls, but new investigations reveal that a more likely cause is progradation of coarse-grained tributary fans across the narrow river valley downstream of the main area of floodplain wetland. Obstruction of trunk river flow and sediment transfer by these tributary fans has led to backponding and upstream gradient reduction and to accumulation of valley fills up to 35m thick. Chronological control for the timing and rate of sediment accumulation is limited, but we hypothesise that a semi-arid to arid climate, characterised by asynchronous trunk-tributary activity that results in marked discontinuities in downstream water and sediment transfer, is likely to have been a key control. These interpretations are supported by other studies of dryland rivers globally and the findings add to our growing understanding of the controls on the origin and development of southern African wetlands, particularly by demonstrating how the combination of a particular physiography and a dryland climate can impart some distinctive geomorphological characteristics. © 2011 Copyright Society of South African Geographers.

Authors


  •   McCarthy, Terence S. (external author)
  •   Tooth, Stephen (external author)
  •   Jacobs, Zenobia
  •   Rowberry, M D. (external author)
  •   Thompson, Mark C. (external author)
  •   Brandt, Dion (external author)
  •   Hancox, P John. (external author)
  •   Marren, P M. (external author)
  •   Woodborne, Stephan (external author)
  •   Ellery, W N. (external author)

Publication Date


  • 2011

Citation


  • McCarthy, T. S., Tooth, S., Jacobs, Z., Rowberry, M. D., Thompson, M., Brandt, D., Hancox, P. John., Marren, P. M., Woodborne, S. & Ellery, W. N. (2011). The origin and development of the Nyl River floodplain wetland, Limpopo Province, South Africa: trunk-tributary river interactions in a dryland setting. South African Geographical Journal, 93 (2), 172-190.

Scopus Eid


  • 2-s2.0-84857019019

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/3607

Has Global Citation Frequency


Number Of Pages


  • 18

Start Page


  • 172

End Page


  • 190

Volume


  • 93

Issue


  • 2

Abstract


  • The Nyl River floodplain wetland, one of South Africa's largest floodplain wetlands and a Ramsar site of international conservation importance, is located in an area of long-term and still active valley sediment accumulation. Creation of accommodation space for sedimentation has previously been attributed to tectonic controls, but new investigations reveal that a more likely cause is progradation of coarse-grained tributary fans across the narrow river valley downstream of the main area of floodplain wetland. Obstruction of trunk river flow and sediment transfer by these tributary fans has led to backponding and upstream gradient reduction and to accumulation of valley fills up to 35m thick. Chronological control for the timing and rate of sediment accumulation is limited, but we hypothesise that a semi-arid to arid climate, characterised by asynchronous trunk-tributary activity that results in marked discontinuities in downstream water and sediment transfer, is likely to have been a key control. These interpretations are supported by other studies of dryland rivers globally and the findings add to our growing understanding of the controls on the origin and development of southern African wetlands, particularly by demonstrating how the combination of a particular physiography and a dryland climate can impart some distinctive geomorphological characteristics. © 2011 Copyright Society of South African Geographers.

Authors


  •   McCarthy, Terence S. (external author)
  •   Tooth, Stephen (external author)
  •   Jacobs, Zenobia
  •   Rowberry, M D. (external author)
  •   Thompson, Mark C. (external author)
  •   Brandt, Dion (external author)
  •   Hancox, P John. (external author)
  •   Marren, P M. (external author)
  •   Woodborne, Stephan (external author)
  •   Ellery, W N. (external author)

Publication Date


  • 2011

Citation


  • McCarthy, T. S., Tooth, S., Jacobs, Z., Rowberry, M. D., Thompson, M., Brandt, D., Hancox, P. John., Marren, P. M., Woodborne, S. & Ellery, W. N. (2011). The origin and development of the Nyl River floodplain wetland, Limpopo Province, South Africa: trunk-tributary river interactions in a dryland setting. South African Geographical Journal, 93 (2), 172-190.

Scopus Eid


  • 2-s2.0-84857019019

Ro Metadata Url


  • http://ro.uow.edu.au/scipapers/3607

Has Global Citation Frequency


Number Of Pages


  • 18

Start Page


  • 172

End Page


  • 190

Volume


  • 93

Issue


  • 2