This study examines foredune evolution along a 2100 m section of coast adjacent to the Tugela
River. The foredunes vary in both height and shape along the study area and form the southern
most extension of the Tugela foredune-ridge plain. Sand accumulation and erosion was
measured at regular intervals over a 30 month period by tacheometric surveys.
The foredunes and beaches are comprised of over 99 % sand. The sediment was predominantly
composed of quartz and feldspar with subordinate lithic fragments. The quartz grains display
conchoidal fractures and mechanical v-shaped pits and curved grooves. The beach and dune
sand is well sorted and slightly negatively skewed with a mean grain size of 1.62 ф.
The vegetation structure and floristic composition of the foredunes are explored. A range of
factors influencing foredune morphology and evolution, including canopy density, height and
distribution, wind velocity and a variety of ecological and environmental processes are examined.
Ridge and swale morphology as well as alongshore variation in the dunefield could not be related
to biological processes.
The development of a foredune-ridge topography depends on a large sediment supply from the
Tugela River over the long-term. Periods of high discharge introduce a fresh source of sediment
to the littoral zone. Reworking of fluvial sediment landwards results in wide beaches. Onshore
winds transport the sand from the beaches to the foredunes. Scaevola thunbergii encourages
rapid vertical accretion and hummock dunes are formed. Lateral extensive invasion by seedlings
may result in the hummock dunes joining to form coast parallel foredunes. Under periods of
reduced sediment discharge erosion of the shoreline results in steep narrow beaches. Despite a
negative beach budget foredunes continue to accrete vertically. Marine erosion results in either
the complete destruction of embryo foredunes or their landward shift. Natural breaks in the
dune crestline were attributed to changes in the delivery of sediment to the beaches. The
processes operating in the study area conform to Psuty's (1988,1989) sediment budget model of
foredune development. Sediment availability to the coastline produces characteristic
morphologies. / Thesis (M.Sc.)-University of Natal, Durban, 1998.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/3991 |
| Date | January 1998 |
| Creators | Olivier, Mervin John. |
| Contributors | Garland, Gerry G. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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