Die noordwaartse begrensing van die duinsee van die sentrale Namib langs die benede-Kuiseb

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The Kuiseb River in South West Africa sharply delineates the Namib Sand Sea in the north, between Hudaob and Rooibank. The increasing rate of groundwater extraction from the Kuiseb's dry river course has led investigators to presume that the lowering of the river's groundwater table may eventually result in dune migration northwards, across the Kuiseb River, with accompanying negative effects on the whole ecosystem in the area as far west as Walvis Bay. In this study, 132 samples of dune sand and 76 samples of sand from the Kuiseb River were analysed by sieving, optical and computer methods. Statistically significant differences regarding median phi, average grain size, sorting, roundness and heavy mineral contents between dune and river sands were obtained, indicating that the present amount of dune sand being shed in the Kuiseb River bed is insignificant. Wind data for four stations in the area was analysed in terms of the geomorphologically effectiveness thereof. Wind velocities of > 16 km/h and their frequencies were used to calculate average annual and resultant sand transportation vectors, using Bagnold's and Landsberg's formulae. From the interior to Rooibank, resultant sand transport vectors indicate a net annual displacement of sand generally southernly of the Kuiseb River, while the resultant for Walvis Bay is northeast. Keywords: Namibia, Namib Desert, Kuiseb River, climate, geology, botany, geomorphology, fog, groundwater extraction, groundwater table, dune migration, sand movement, grain size, sand transport. ACCESSION NUMBER: 551'688 HAR (A).

University of Stellenbosch
PhD Thesis
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