In 1884 gold was discovered in South Africa. Two years later, Johannesburg was founded at this site, and ten years thereafter 100,000 people lived in the new booming city. By this time it was the largest city in South Africa, outgrowing the 200 year older Cape Town. Today, Johannesburg—known by the nickname ‘Joburg’—has a population of about 8.4 million people, making it the largest city in the country and, curiously, the largest city on earth not set on water; be it the ocean, a lake or river. The city is estimated to have the largest economy of any Sub-Saharan city, accounting for about 43 per cent of South Africa’s GDP—as well as being home to Africa’s largest stock exchange and the continent’s biggest and busiest airport. Despite this abundant wealth, Joburg inherited a deep divide from its colonial past and years of brutal apartheid rule. This divide manifests in a massive socio-economic gap between the city’s north and south. With 33 per cent of homes not having access to electricity. The city is forecast to double its size by 2040, which will likely intensify some of issues it currently faces.
Johannesburg is located on the Highveld Plateau, a highland with an elevation of 1,753 metres above sea level. The city’s elevation and distance from bodies of water shape its climate significantly. Johannesburg experiences an average high/low temperature of 25.4/14.7°C in January and 16.7/4.1°C in July. In summer, it often gets hot days followed by coolish nights, sometimes chilled by afternoon thunderstorms which bring most of the city’s 713mm annual rainfall. Winter is usually dry and sunny, with cold nights, and occasional frosts. The city experiences high levels of ultraviolent radiation due to its relative proximity to equator.
Johannesburg’s Climate Change Adaptation Plan is laid out in a 2009 document. This report highlights the risks of urban flooding, a problem which is the result of Johannesburg’s frequent summer storms in combination with a multitude of interacting issues, such as loss of natural drainage areas, increases in hard surfaces and inadequate storm-water infrastructure and maintenance. These risks are projected to intensify in the near future as a result of climate change and will likely cause a risk to lives, damage to water supply and sanitation, and stress on transit, electrical and telecom systems.
To adapt to these risks, Johannesburg as created new stormwater by-laws which are now being applied across the city. In many places, the above risks are exacerbated by the large number of informal settlements in flood prone areas, often without any infrastructure to deal with the deluge. As part of a city wide investment in infrastructure, in 2014 Johannesburg gave sixty-nine families ‘Informal Disaster Resilient Structures’ in the in Setjwetla Informal Settlement, Alexandra. This is one of the oldest townships in the city, and its location on the banks of the Jukskei River sees these homes at constant risk of flooding. The new rules also seek to prevent further settlements forming in flood prone areas, and to relocate informal dwelling already existing within flood basins. This is a very controversial issue, particularly as Johannesburg is set to received a large number of climate change related migrants.
These new laws incorporate aspects of Sustainable Urban Drainage Systems (SUDS), a body of knowledge and practice which seeks to reduce potential flooding in new and existing urban areas and achieve ecological benefits. SUDS begins with a critique of traditional storm-water drainage techniques, which seek to move water off surfaces and into pipes as quickly as possible. This can silt up streams, spread pollution, erode soil and result in large quantities of fast-moving water, which can be dangerous. In contrast to this, SUDS attempts to manage storm-water where if falls by minimizing impervious ground cover like cement, allowing water to seep into the ground, as well as techniques for capturing and storing storm-water on site so it can be released in a controlled fashion. This is done through engineering techniques such as permeable paving, green roofs, ‘soakaways’, and groundwater replenishing wells. Many of these have multiple advantages, for instance green roofs catch and hold rainwater, have potential biodiversity benefits and can reduce the need for cooling and hence lower energy expenditure.