Sea level rise caused by global warming is already
causing damage to public and private coastal property in Cape Town. In some
areas retreat to higher ground may be necessary.
The coast at Milnerton particularly is being
affected by erosion, with the public beach already having been washed away by
erosion and storm surges. The city is currently assessing options which include
retreat for a section of the coast in Milnerton, says mayco member for spatial
planning and environment Marian Nieuwoudt.
At a public participation meeting on the draft Coastal Bylaw on 15 August,
Nieuwoudt said a report by newly appointed city engineers was on her desk,
which identified risks on the city’s coastline.
Other than Milnerton, there are numerous other areas on Cape Town’s coast being
affected, such as Glencairn, Hout Bay, and Seapoint.
She said coastal infrastructure and amenities have been underfunded and now
require “significant investment” and “immediate survival maintenance” was
required for coastal infrastructure.
“A specific concern to the city is that public and private infrastructure will
become increasingly at risk to coastal processes such as erosion, and beaches
as public recreational spaces are likely to become increasingly at risk in
developed areas of the metro in the long-term”.
At the meeting Nieuwoudt said “We may need to retreat and allow nature to
provide a barrier to the ocean.”
In the last financial year the city spent R13.5m on repairs and rehabilitation
of damaged coastal infrastructure, and R66m has been earmarked for current
projects.
Money spent to date:
- Fishermans
Lane parking revetment: R3.5m - Big Bay
rehabilitation: R3.8m - Clifton
walkway repair: R200,000 - Hout Bay
dune rehabilitation: R6m (ongoing)
Projects underway with
funding:
- Fishermans
Lane upgrade: R26m - Demolition
of derelict infrastructure at Macassar pavilion and defunct ablutions: R5m - Glencairn
Beach precinct upgrade: R3.5m
Nieuwoudt noted the importance of natural barriers such as dunes and wetlands, many of which have been compromised by development or the canalisation of estuaries. These needed to be restored as much as possible, and the city was seeing some success in the ongoing restoration of the natural sand dunes in Hout Bay, an ongoing project where R6m had been spent so far.
Rehabilitation projects such as these also created job opportunities, as in Hout Bay where a team was employed to check and repair the rehabilitation netting on a daily basis.
The Coastal Management Programme, published in 2015, noted that coastal erosion is occurring at “a number of points along the city’s coastline as a direct result” of urban development. The report gives an example: at the southern end of Table Bay the coast has been eroded by 35 metres over the last 45 years. Climate change is predicted to increase both the intensity and frequency of coastal storms, worsening the erosion problem and creating a long term risk to the city.
Global consensus at the time of the report suggested a mean sea level rise of 0.76m by 2100. Although this may seem small, it will cause “disproportionately large impacts on the damage that storms cause to the coastal zone”.
International Intergovernmental Panel on Climate Change (IPCC) author and researcher at the African Centre for Cities Anton Cartwright authored one of the first series of studies on the impacts of sea level rise for Cape Town in 2008. He said in the intervening 11 years the pace of melting of terrestrial ice in Antarctica and Greenland, a major contributor to sea level rise, had surpassed all projections and the projected rate of sea level rise has had to be adjusted.
The IPCC Special Report on 1.5°C released last year, which Cartwright says “tried to be optimistic” notes the likelihood of the ocean rising more than a metre in the next 80 years. This is higher than the predicted 2cm per decade estimated in 2008.
In phase three of the study for the Sea-Level Rise Risk Impact Assessment he conducted for the city, three scenarios of damage due to storm surges were modelled. The scenarios were a 2.5m storm surge, a 4.5m storm surge, and a 6.5m storm surge. The damage, based on insurance risk assessments, on private property alone was R3.2bn, R19.5bn, and R44.4bn respectively. These figures were based on 2008 rates assessments.
At the time, he calculated a 95% chance of a 2.5m storm surge occurring in the next 25 years, with the chance of a 4.5m storm surge at 85% and a 6.5m surge at 20%. He says the 2.5m storm surge already occurred in June 2017.https://www.bizcommunity.com/Article/196/702/195053.html
