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Sandy shorelines occupy ca. 80% of the coast of Mozambique, South Africa and Namibia. A geomorphological classification of sandy shorelines in the subcontinent identifies twelve major categories in four sub-regional coastal systems. The behaviour of each of the major shoreline types under rising sea level is outlined based on geological principles together with observations of former shorelines preserved onshore and on the continental shelf. Human adaptation strategies regarding shoreline change involve a binary choice (hold the shoreline in place or permit it to fluctuate) and these exert an equally important control on sandy shoreline response in the medium term as does sea-level rise itself. It is anticipated that densely urbanised sandy shorelines will be stabilised by coastal defences involving both capital works and ongoing maintenance that will be accompanied by deterioration and ultimate loss/replacement of the natural ecosystem. In contrast, currently undeveloped, natural shorelines will be permitted to adjust and will, as a consequence, survive and continue to deliver ecosystem services. The major challenge for climate-change adaptation lies in those lightly urbanised coastal areas where relatively small numbers of property owners may be, or perceive themselves to be, at risk of economic loss from shoreline change. In such cases the choice is between preserving those property interests (through sea defences) and preserving the sandy shoreline and its human and ecosystem services (via retreat). [ABSTRACT FROM AUTHOR]

The tidal records of existing South African and Namibian tide gauges are examined and corrected. Regional sea level trends vary, with the West Coast rising by +1.87 mm y-1 (1959-2006), the southern coast by +1.48 mm y-1 (1957-2006) and the East Coast by +2.74 mm y-1 (1967-2006). The effects of barometric pressure and vertical crustal movement changes on these trends are examined. The derived relationship between sea levels and barometric pressure changes varied between 5.71 and 7.67 mm hPa-1, significantly less than the theoretical inverse barometric correction. Barometric pressure has been dropping along the west coast at 1.63 hPa per decade (1987-2006), has remained fairly static along the southern coast and is rising at 0.30 hPa per decade (1970-2007) along the east coast of southern Africa. The West Coast barometrically corrected sea level trends show that most of the change can be attributed to falling barometric pressure, whereas along the East Coast, the barometric pressure increase is suppressing sea level by 0.2 mm y-1. Vertical crust movements vary, with the largest recorded movements of +1.11± 0.25 mm y-1 found along the East Coast. Movement rate reduces southwards. Eustatic sea level trends vary from +3.55 mm y-1 along the East Coast and +1.57 mm y-1 along the southern coast to +0.42 mm y-1 along the West Coast. [ABSTRACT FROM AUTHOR]