Flooding dynamics in a large low-gradient alluvial fan, the Okavango Delta, Botswana, from analysis and interpretation of a 30-year hydrometric record

P. Wolski (1) , M. Murray-Hudson (1)

1 Harry Oppenheimer Okavango Research Centre

The Okavango Delta is a flood-pulsed wetland, the resources of which support a large tourism industry and subsistence of the local population. In order to obtain an insight into the influence of various environmental factors on flood propagation and distribution in this system, an analysis was undertaken of a 30-year record of hydrometric data (discharges and water levels) from one of the Delta distributaries. The analysis revealed that water levels and discharges at any given channel site in the analysed distributary are influenced by a complex interplay of flood wave and local rainfall input modified by channel-floodplain interactions, in-channel sedimentation and technical interventions, both at the given site and upstream. Additionally, cyclical variation of channel margin vegetation due to nutrients recycling might play a role. It was shown that data from channels do not adequately represent flood dynamics and its change at the distributary level. The paper contributes to the understanding of seasonal and long-term flood pulsing and their changes in low gradient systems of channels and floodplains.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

P. Wolski, M. Murray-Hudson. Flooding dynamics in a large low-gradient alluvial fan, the Okavango Delta, Botswana, from analysis and interpretation of a 30-year hydrometric record. Hydrology and Earth System Sciences Discussions, 2005, 2 (5), pp.1865-1892. ⟨hal-00298706⟩