Projected inundations on the South African coast by tsunami waves

Historical and recent evidence recorded along the South African coast suggests that five tsunami events have occurred since 1960. These were mostly associated with trigger mechanisms associated with sources of remote submarine seismicity along far-field subduction zones and local atmospheric disturbances (meteotsunami). The passive margin of the South African West Coast, and the broad Agulhas Bank spanning the South- and Southeast coasts, have contributed to an increased susceptibility to inundation of waves in the adjacent low-lying coastal areas in these regions. In the published models and empirical studies for South Africa, the bathymetry and orientation of Port Elizabeth Bay is seen to amplify effects of a tsunami wave. Other regions including the Cape Town and St Helena Bay areas are also vulnerable to coastal inundation through the data generated in this study. The methodology presented here provides a simple means of determining the susceptibility of coastal areas to significant inundation by far-field tsunamis

An assessment of coastal vulnerability for the South African coast

Coastal vulnerability is the degree to which a coastal system is susceptible to, or unable to cope with, adverse effects of climate change. One of the most widely used methods in assessing risk and vulnerability of coastlines on a regional scale includes the calculation of vulnerability indices and presenting these results on a vulnerability map. These maps can assist coastal managers, planners, landowners and stakeholders identify regions of greater risk to coastal hazards and ultimately better inform mitigation and development strategies.This paper discusses the creation of a coastal vulnerability map for South Africa. The criteria used included elevation to chart datum, beach width, tidal range, wave height, geology, geomorphology, anthropogenic activities, distance to 20m isobaths and relative sea level change. The values of these parameters were divided into classes and the various classes ranked on a scale of 1 (very low vulnerability) to 5 (very high vulnerability) using examples from literature and expert knowledge. The layers were combined using the spatial overlay (map algebra) technique to create the final map. The results highlight the most vulnerable areas along the coastlines as the areas surrounding the City of Cape Town (the west coast) and the regions close to East London and Port St. Johns on the east coast. This can be mainly attributed to the type of geology and the anthropogenic activities in these areas

The influence of wave action on coastal erosion along Monwabisi Beach, Cape Town

The coastline to the east of the Monwabisi Beach tidal pool has been subject to substantial visible coastal erosion. Monwabisi is located near the City of Cape Town and is situated along the northern coastline of False Bay. The erosion that has occurred has raised concern as it is damaging local infrastructure. The coastline retreat to the east of Monwabisi was investigated through analysis of aerial photographs and wave data to establish whether there is a relationship between dynamic wave action that this bay is subjected to, and the observed erosion within the study area. The maximum lateral coastal erosion at the Monwabisi study area from 2003 until 2014 was approximately 30m in a landward direction. Based on the correlation of the results between the rate of coastline retreat and the wave data, the study has concluded that the extreme rates of coastline retreat experienced within the study area at Monwabisi is most likely a direct result of a combination of influences including the number and height of big wave events, waves coming from a more southerly direction, the underlying geological substrate of the study area, and the impact that the local infrastructure has had on the geological substrate. Three time periods of maximum monthly erosion rates occurred from June 2008 to November 2009, March 2010 to March 2011 and April 2011 to June 2012

Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa

There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit

Strontium isotope investigation of ungulate the Pleistocene Paleo-Agulhas Plain of the greater South Africa

Middle Stone Age sites located within the Greater Cape Floristic Region on the South African southern coast have material culture with early evidence for key modern human behaviors such as projectile weaponry, large animal hunting, and symbolic behavior. In order to interpret how and why these changes evolved, it is necessary to understand their ecological context as it has direct relevance to foraging behavior. During periods of lowered sea level, a largely flat and vast expanse of land existed south of the modern coastline, but it is now submerged by higher sea levels. This exposed area, the Paleo-Agulhas Plain, likely created an ecological context unlike anything in the region today, as evidenced by fossil assemblages dominated by migratory ungulates. One hypothesis is that the Paleo-Agulhas Plain supported a migration ecosystem of large grazers driven by summer rainfall, producing palatable forage during summer in the east, and winter rainfall, producing palatable forage during winter in the west. Alternatively, ungulates may have been moving from the coastal plain in the south to the interior north of the Cape Fold Mountains, as observed for elephants in historic times. In this study, we assess ungulate movement patterns with inter- and intra-tooth enamel samples for strontium isotopes in fossil fauna from Pinnacle Point sites PP13B and PP30. To accomplish our goals we created a bioavailable 87Sr/86Sr isoscape for the region by collecting plants at 171 sampling sites and developing a geospatial model. The strontium isotope results indicate that ungulates spent most of their time on the Paleo-Agulhas Plain and avoided dissected plain, foothill, and mountain habitats located more than about 15 km north of the modern coastline. The results clearly exclude a north-south (coastal-interior) movement or migration pattern, and cannot falsify the east-west movements hypothesized in the south coast migration ecosystem hypothesis