The evolution of the Congo- Kalahari Watershed: African mega-geomorphology

Africa's bimodal elevation, low in the north and west, and high in the south and east, is globally unique. The Congo–Kalahari Watershed represents the transition between low and high Africa. This sub–continental drainage divide separates two of the world's large rivers: the Congo and Zambezi Rivers. This study focuses on the large rivers which form the Congo–Kalahari Watershed. The analysis of their longitudinal profiles, through the use of a geographic information system and remotely sensed imagery and elevation data, provides insights into this drainage divide. The creation of a geodatabase on river knickpoints, featuring geographic and geologic attributes for 18 longitudinal river profiles represented by 194 047 elevation points (19 700 km), identifies a total of 380 knickpoints, 243 of which have heights larger than 5 m. It is possible to assign a probable cause to 354 of all the knickpoints identified in this study, highlighting the underlying geology as a significant control with tectonics playing a secondary role. The following rivers are studied: Chambeshi, Congo, Kalungwishi, Kasai, Kwango, Luapula, Lufira, Lukuga, Lulua, Luvua and Wamba (Congo Basin) and the Cubango, Cuchi, Kabompo, Kafue, Luena and Upper Zambezi Rivers (Kalahari Basin). It is argued that the Congo–Kalahari Watershed is a trimodal feature comprising of a western, central and eastern zone. The smooth central region of the divide is the oldest and has been relatively stable since the break–up of Gondwana. The western region is topographically rougher and has undergone substantial change in the Cenozoic becoming bifurcated by the headwater erosion of the coastal rivers. The eastern watershed is the youngest and topographically roughest, having been substantially modified in the Neogene due to tectonic activity associated with the extension of Western Branch. Due to the extensive modification, this eastern zone should be considered a new feature. The acknowledgment of these three landscapes may lead to the conciliation of various interpretations and suggested causes of Africa's present day continental geomorphology.

Grantor dc:publisher.institution

Department of Environmental and Geographical Science

Year dc:date.issued

2014

Author dc:creator

• Flugel, Tyrel James

Advisors dc:contributor.advisor

• Eckardt, Frank
• Cotterill, Fenton

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/8695

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/8695