Headland bypass dunes on the South African coast: 100 years of (mis)management
McLachlan, A.; Burns, M. (1992). Headland bypass dunes on the South African coast: 100 years of (mis)management, in: Carter, R.W.G. et al. Coastal dunes: geomorphology, ecology and management for conservation: Proceedings of the 3rd European Dune Congress Galway, Ireland, 17-21 June 1992. pp. 71-79
In: Carter, R.W.G.; Curtis, T.G.F.; Sheehy-Skeffington, M.J. (Ed.) (1992). Coastal dunes: Geomorphology, ecology and management for conservation: Proceedings of the 3rd European Dune Congress Galway, Ireland, 17-21 June 1992. A.A. Balkema [etc.]: Rotterdam. ISBN 90-5410-058-3. 533 pp., meer
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| Abstract |
The south coast of Africa consists of large zetaform bays which are characterised by extensive eastward sand transport. Wave and wind directions are such that large volumes of sand are blown onshore at the open eastern ends of these bays. This sand then travels over the headlands in the form of transgressive sheets of transverse dunes, termed headland bypass dunefields. This paper examines three such dunefields and the impacts of man on them over the past century. 1. The Driftsands dunefield crossed the Cape Receife headland at Port Elizabeth and originally sparmed 18 km. At its peak in the 1850s it was discharging 175000 m³ of sand into Algoa Bay annually. Seen as a threat to parts of the city, it was stabilised at the turn of the century, the local authorities using convict labour to spread city refuse and plant exotic wattles to fix and stabilise the sand. With this sand source cut off, Port Elizabeth beaches today have erosion problems. 2. The St Francis dunefield crosses the Cape St Francis headland and is 16 km long. Situated in a rural area, it was left largely intact until the 1970s when its downwind end and some nearby dunes were stabilised to develop holiday resorts. Beaches in this area are now eroding. 3. A headland bypass dunefield at Waenhuiskrans, near Cape Agulhas, was stabilised earlier this century by the Department of Forestry. Subsequent erosion of downwind beaches prompted the suggestion that it be destabilised to re-initiate sand supply to resort beaches. Limited destabilisation was undertaken and sand is starting to enter the beaches again. Modifying such dune systems causes major disruption of littoral sand transport and has serious longterm implications. These implications were not understood when active 'management' was first initiated. |
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