Cape Town Climate Condition
South Africa is a semi-arid country, with seasonal and unevenly distributed rainfall (Friedrich et al., 2009). South Africa ranks as the 30th driest nation in the world due to its annual average rainfall of less than 500 mm (as opposed to the global average of 869 mm) (DWA, 2013). Cape Town is the second-largest city in South Africa in terms of population and has the largest inland area (2455 km2). It is located on the southwest coast of the nation in the Western Cape Province. Cape Town has a Mediterranean climate with mild, wet winters and dry, hot summers.
Cape Town is significantly dependent on surface water, and the City of Cape Town derives 98 percent of its water from surface water sources from 6 major dams on the city’s outskirts (City of Cape Town, 2017; OECD, 2021). South Africa has been undergoing a country-wide drought from 2015 to 2018, with the Western Cape region and the City of Cape Town (CoCT) being the areas most severely impacted. In 2018, the City of Cape Town announced plans for “Day Zero,” when it is anticipated that the water levels in the main storage dams will drop to dangerously low levels (13.5%). Day zero is the hypothetical day when the municipal water supply would be mostly shut off, and locals would only be permitted to draw water from the specified collection points with daily consumption of no more than 25 liters per person (Schreiber, 2018).
Additionally, a warmer and drier environment is predicted for Cape Town, along with an increase in the frequency and intensity of extreme weather occurrences. The more intense weather would not only increase the risk to Cape Town’s freshwater resources, but it would also hasten the spread of water-thirsty alien plant species in Cape Town’s essential cathcment areas, which would result in an estimated annual loss of 30 million m3 of water supply (Schreiber, 2018).
Cape Town Stormwater Policy
The Management of Urban Stormwater Impacts Policy, published by the City of Cape Town in 2009, acknowledged the significance of preserving and strengthening ecological services in the face of climate change. The city further acknowledges that the creation of impervious surfaces through urban development directly contributes to negative effects such as declining water quality, declining groundwater recharge and quality, stream channel degradation, increasing flooding events, expanding flood plains, and loss of ecosystem integrity and biodiversity (Roads and Storm Water Department, 2009). The policy’s goals include implementing best management practices (BMPs) to protect human health, preserve natural aquatic habitats, enhance and sustain recreational water quality, and lessen the impact of flooding on local economies and community livelihoods (Roads and Storm Water Department, 2009). The policy further recognizes the significance of source controls (a non-structural or structural best management practices) to control the quantity and quality of stormwater runoff and to encourage the natural groundwater recharge in order to minimize the generation of excessive stormwater and pollution at or near the source.
This policy serves as a guide for the initial movement for the City of Cape Town to become a water sensitive city, and the adoption or enforcement of such environmental concerns can open up opportunities for green roofs as a BMP option for developers who want to abide by stormwater management concerns. The Stormwater Bylaw of Cape Town contains two sections that offer incentives for the use of green roof technologies in Cape Town. According to section 6.2.7: Integration with the environment, the BMPs should increase urban biodiversity, and improve the amenity and aesthetics of the development site and its surroundings. According to section 6.2.8 Incentive schemes, the city may, if necessary, implement incentive programs to encourage and facilitate the adoption of WSUD measures by private developers and individual households (Armstrong, 2010)
Existing Green Roof Projects
In South Africa, the concept of green roofs is still quite new, and there aren’t many publications about the green roof projects in Cape Town. According to research, two intensive garden roofs were installed in 2000 and 2006 on buildings owned by the city. The “sixth floor” project, implemented in 2000 on the podium of the Cape Town Civic Centre in accordance with the municipality’s water-wise policy, was the first commercial application of an indigenous roof garden that featured a water-wise design in the City of Cape Town.
Nevertheless, Durban has implemented green roofs far more extensively than Cape Town. The eThekwini Municipality in Durban initiated the first green roof pilot project in South Africa, and the city has been implementing a Municipal Climate Protection Program since 2006. As a part of this program, the green roof pilot project started in 2008. It involved the construction of eight green roofs, each of which featured a variety of plants, growing mediums, and green roof techniques constructed on a city building. Additionally, it is important to note that the eThekwini Municipality’s green roofs were listed as one of the efficient stormwater management strategies in the Municipal Adaptation Plans.
Challenges and Recommendations to decision makers in Cape Town
Although Cape Town’s current policies (Stormwater policy & Green City Guidelines) are favourable towards implementing the green roofs, there are still very limited green roof projects (only two) that has been implemented in the Cape Town settings. It is also noted that the lack of political support, financial difficulties of the government, fragile socioeconomic structures, and lack of local research are the four main barriers that hinder the implementation of green roofs in Cape Town. In terms of the technical aspects, based on the best available knowledge estabished by this review, the recommended green roof design is extensive green roof, with indigenous plantation and local soil and waste as the growing medium. In order to address the other challenges, it is recommended to 1) conduct green roof pilot projects in Cape Town by using Durban’s green roof project as a reference 2) create local guidelines and hold public training sessions or workshops on green roofs 3) conduct cost-benefit analysis on green roofs specific to the Cape Town area 4) carry out community outreach and engagement initiatives to educate low-income homeowners about the value of green infrastructures.
Reference
Friedrich, E., Pillay, S., & Buckley, C. A. (2009). Carbon Footprint analysis for increasing water supply and sanitation in South Africa: A case study. J.Clean.Prod, 17, 1–2.
DWA. (2013). National Water Resource Strategy: Water for an Equitable and Sustainable Future (pp. 1689–1699). Department of Water Affairs.
City of Cape Town. (2017). Water Services and the Cape Town Urban Water Cycle. City of Cape Town.
OECD. (2021). Water Governance in Cape Town, South Africa. OECD Studies on Water, OECD Publishing, Paris. https://doi.org/10.1787/a804bd7b-en
Schreiber, L. (2018). Keeping the Taps Running: How Cape Town averted ‘Day Zero,’ 2017-2018. Princeton University.
Roads and Storm Water Department. (2009). Management of Urban Stormwater Impacts Policy (C 58/05/09). Catchment, Stormwater and River Management Branch, City of Cape Town.
Armstrong, J. T. (2010). Extensive Green Roof Design in the City of Cape Town: Barriers and Opportunities for developing a green industry. University of Cape Town.
Shafique, M., Kim, R., & Rafiq, M. (2018). Green roof benefits, opportunities and challenges – A review. Renewable and Sustainable Energy Reviews, 90, 757–773. https://doi.org/10.1016/j.rser.2018.04.006
Armstrong, J. T. (2010). Extensive Green Roof Design in the City of Cape Town: Barriers and Opportunities for developing a green industry. University of Cape Town.