Cape Town - A study monitoring shoreline changes along the south-western coast of South Africa over the past 83 years has found that one of South Africa’s longest beaches, 16 Mile Beach in Yzerfontein, was eroding at an accelerating pace with a significant portion already disappearing under the ocean.
The researchers who authored the study said without proper management and more public participation in coastal protection, large parts of the coastline may continue to wash away.
In her Master’s thesis, Jennifer Murray – a Wits student at the School of Geography, Archaeology and Environmental Studies – and her research team explore how much the beach has changed over the years and the long-term effects of these changes.
They did this using a mix of “old school” digitising of historical aerial photographs and “more modern” machine-learning automated processes with satellite imagery to measure how the shoreline has changed.
Murray explained this study, and many of the changes observed, was prompted by the effects of two large storms which hit the Western Cape in 2017 (around the same time as the Knysna fires) and significantly battered the beach at Yzerfontein.
“We found that this coastline is indeed very dynamic and has been shifting backwards, and forwards, between the time periods (from 1937 to 2020).
“The average net shoreline movement is closer to 39 metres of erosion, with a particular section of 16 Miles eroding almost 100 metres.
“But even so, a different section also moved 18 metres out to sea, which shows how dynamic this is,” Murray said.
The study states that coastal erosion was increasingly becoming a public issue and was no longer just a problem for coastal managers. The consequences of coastal erosion included loss of life, disruption of economic sectors, and degradation of ecosystems and biodiversity.
“Therefore, to protect coastal infrastructure and its socio-economic potential, it is necessary to monitor coastal areas actively and evaluate their time-space patterns,” the study stated.
Mary Evans, senior lecturer at the School of Geography, Archaeology and Environmental Studies, said the management of coastal areas needed to be considered, especially as these sandy beaches needed to be protected and maintained to prevent the degree of erosion they were currently seeing.
“While we look to local government and coastal managers to protect the coast, the public needs to be aware of the problems around coastal erosion and its impacts and need to actively participate in its protection,” Evans said.
Without proper management, Evans said large parts of the coastline, and therefore beaches, may wash into the ocean.
This study: “Monitoring Shoreline Changes along the South-western Coast of South Africa from 1937 to 2020 Using Varied Remote Sensing Data and Approaches”, was recently published in the Remote Sensing journals by Murray, Evans, Elhadi Adam, Stephan Woodborne, Duncan Miller and Sifiso Xulu.