Goble, B.J. and MacKay, C.F., 2024. Cumulative natural and human impacts alter cyclical dynamics of a South African shoreline: An extended summary. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 289-293. Charlotte (North Carolina), ISSN 0749-0208.

Coastlines are spatio-temporally dynamic with a range of physical processes at play. As attractive landscapes with multiple open spaces for recreation, habitation and delivering various goods and services, coastlines attract a plethora of human developments. In developing countries, human movement from the hinterland to access space and resources, coupled with competition for space for multiple types of uses and developments, has meant that these coasts are rapidly changing. This is exacerbated by projected long-term effects of climate-driven impacts, the most important of which is accelerated shoreline change, which results in significant changes to the natural coastal functioning. Coastal anthropogenic changes often create high-risk zones and damage to critical infrastructure. Thus, an understanding of shoreline change, and the drivers thereof are critical for management responses and long-term planning. This study assesses the causes of changes to natural shoreline dynamics on a historically accreting coastline on the northeast coast of South Africa. Shoreline positions dating from 1937 are assessed using the Digital Shoreline Analysis System (DSAS, developed by the USGS), a widely accepted approach for the analysis of rates of change. In line with accepted practice, the preferred statistical rates assessed were the net shoreline movement (NSM) and the endpoint rate (EPR). This naturally dynamic region has experienced erosive and accretive cycles, with accretion dominating until 2007. Thereafter, the trend was a significant overall shift to persistent erosion along the southern section of the study area. A significant coastal storm event was experienced in 2007 which appeared to initiate this new cycle of persistent erosion. It is proposed that the change in accretion-erosion dynamics in favour of a mostly eroding section of coast is likely related to the cumulative impacts of various changes within this natural system, largely anthropogenic, which has led to - significant reduced sediment loads reaching the coast. To this end, coastal management actions need to consider the combination of far field changes to coastal systems that may influence widescale morphological change, influencing coastal safety and economic stability.