The February 2000 floods on the Letaba River, South Africa: an examination of magnitude and frequency

Abstract

Accurate estimates of the magnitude of the floods that affected southern Africa in February 2000 are difficult to obtain since floodwaters damaged the majority of gauging stations on affected rivers. It is possible to estimate the peak discharge experienced in the Letaba River in the Kruger National Park by simulating the hydraulic and geometric characteristics of the peak flow and relating these to the roughness of the channel. Peak water surface slope data were determined from debris and mudline measurements at breaks in channel type. These data are combined with published high-flow channel resistance coefficients for different channel types to generate peak flow estimates for eleven different cross-sections, located between tributaries to allow for sub-catchment contributions to be estimated. In February 2000 flow peaked at approximately 4000 nWs near to Black Heron Dam (in the west of the park), and increased to approximately POOOm^s just upstream of the confluence with the Olifants River. Comparison with gauge records indicates that the February 2000 peak was higher than any flow during the proceeding four decades.