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The 550 km-long KwaZulu-Natal coast broadly divides into a bedrock-framed southern section and northern coastal plain section, each of approximately equal length. Seven types of coastal dune are identified on this coast: estuary barrier dunes; mainland beach foredunes; prograded beachridge dunes; headland bypass dunes; transverse dune fields; parabolic/migrating dunefield; and climbing dunes. The development and distribution of the various dune forms is more strongly controlled by the geological setting, than the aerodynamic regime. [ABSTRACT FROM AUTHOR]

The behaviour of offshore-directed winds over coastal dune and beach morphology was examined using a combination of modelling (3-D computational fluid dynamics (CFD)) and field measurement. Both model simulations and field measurements showed reversal of offshore flows at the back beach and creation of an onshore sediment transport potential. The influence of flow reversals on the beach-dune transport system and foredune growth patterns has previously received little attention. Detailed wind flow measurements were made using an extensive array of mast-mounted, 3-D ultrasonic anemometers (50 Hz), arranged parallel to the dominant incident wind direction. Large eddy simulation (LES) of the offshore wind flow over the dune was conducted using the open-source CFD tool openFOAM. The computational domain included a terrain model obtained by airborne LiDAR and detailed ground DGPS measurements. The computational grid (~22 million cells) included localized mesh refinement near the complex foredune terrain to capture finer details of the dune morphology that might affect wind flows on the adjacent beach. Measured and simulated wind flow are presented and discussed. The CFD simulations offer new insights into the flow mechanics associated with offshore winds and how the terrain steering of wind flow impacts on the geomorphological behaviour of the dune system. Simulation of 3-D wind flows over complex terrain such as dune systems, presents a valuable new tool for geomorphological research, as it enables new insights into the relationship between the wind field and the underlying topography. The results show that offshore and obliquely offshore winds result in flow reversal and onshore directed winds at distances of up to 20 m from the embryo dune toe. The potential geomorphological significance of the findings are discussed and simple calculations show that incoming offshore and obliquely offshore winds with mean velocities over 13 m s and 7 m s, respectively, have the potential to create onshore-directed winds at the back beach with mean velocities above 3.3 m s. These are above the threshold of movement for dry sand and support previous conclusions about the significance of offshore winds in dune and beach budget calculations. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

O' Connor, M., Cooper, J. A. G., and Jackson, D. W. T., 2007. Morphological behaviour of headland-embayment and inlet-associated beaches, northwest Ireland. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 626 – 630. Gold Coast, Australia, ISSN 0749.0208 Both static and dynamic environmental conditions contribute to the behaviour of coastal sedimentary systems. Sand beaches on the bedrock-framed northwest coast of Ireland exist in two distinct planform settings that offer the opportunity to examine their varying behaviour. Beaches in this region are either located in coastal re-entrants between rocky headlands and backed by vegetated sand dunes or adjacent to the inlets of large sandy estuaries that are themselves located in bedrock valleys. They all have a finite sediment volume due to the deeply embayed coastal morphology and lack of contemporary sediment input. The behaviour of these types of systems over the past 170 years is recorded in historical maps, air photographs and morphological measurements. Preliminary results show that the beaches of inlet-associated systems involve complex exchanges between beach, dunes and tidal delta while headland-embayment beaches cycle sediment between beach and dunes. The inlet-associated beaches are typically more dynamic than the headland-associated beaches, although both are subject to the same range of wave forcing. Inlet-associated beaches appear to show cyclicity in their behaviour that alternates between rapid erosion and accretion at horizontal scales of decametres and timescales of decades. Headland-embayment beaches show relative stability or slow progressive erosion. High magnitude storms, long term patterns of 'storminess' and morphological feedback all offer potential explanations for the behaviour identified. [ABSTRACT FROM AUTHOR]