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Over the last ten days, significant coastal cusps have formed along the coastline between Lagoon Beach and Sunset Beach in Cape Town, resulting in large drops in the beach level in the area of these cusps and the resulting erosion of the adjacent dunes.
This is a natural coastal process that is taking place in an already receding coastline, which has resulted in visually dramatic changes to the shoreline. These effects of general erosion and coastal processes are typically stronger and more pronounced during the stormy winter season in Cape Town.
The sandy beaches along Cape Town’s Atlantic coastline, from Lagoon beach to Sunset beach including Milnerton, are known to be receding or eroding slowly overtime.
Changes in sediment transport processes and sediment supply to the coastal system that have resulted from urban development contribute to this effect.
This sediment transport process, which is essentially beach sand loss in winter and replenishment of sand during summer, has been interrupted by urban development, reducing the summer sand replenishment of beaches, resulting in a net loss over time and therefore coastal erosion.
“A similar erosion event was recorded in July 2018, which also caused similar large focused beach erosion and structural damage at the Milnerton Surf Life Saver Club, the Milnerton Golf Club and Restaurant as well as other localised locations along the coast,” said the City’s Deputy Mayor and Mayoral Committee Member for Spatial Planning and Environment, Alderman Eddie Andrews.
“In between these winter storm events, the beach will slowly recover and new cusps could form. This is a natural and normal coastal process. This normal process is happening in addition to slow erosion, and with it meeting fixed infrastructure results in the dramatic pictures we are seeing along parts of this coastline.”
“The effect of future sea level rise will contribute to this effect and presents a long-term challenge along this stretch of shoreline. The City is monitoring the process and its effects on these beaches. We expect to see a slow recovery of beaches and with a slow net loss of dune width over time. The coastal process driving these changes are of a large scale and influenced by multiple factors. This demonstrates the importance of wide coastal buffers as the best defence to coastal dynamics.”