n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Sand transport at and shoreline response to a breakwater attached to a large tidal pool at Monwabisi, Cape Town : technical paper

Volume 49, Issue 2
  • ISSN : 1021-2019



A beach has formed in the lee of a breakwater (spur: rubblemound structure built parallel to the shoreline) attached to the eastern side of the Monwabisi tidal pool, which is located along the shoreline of northern False Bay near Cape Town. The sediment transport regime at Monwabisi is described in terms of the longshore sand transport, an eddy current that forms in the lee of the spur, the effect of wave reflection against a steep slope, transport through the spur, and wind-blown sand transport. The accretion and stability of Monwabisi beach were investigated by analysing photographs, five topographic surveys, cross-sections, and loss/gain maps from these surveys. Large accretion of sand (in total about 32 000 m3 and up to about 2,5 m vertically) occurred mainly alongside the eastern tidal pool wall and between the original shoreline and the spur. The beach slope varies considerably along Monwabisi beach: from 1:66 to 1:8. Beach profile changes occurred up to a level of +3 m. The beach reached equilibrium approximately 2,5 years afterconstruction of the spur started.

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