Waterway Rehabilitation in Cape Town, South Africa

The rivers and wetlands in the City of Cape Town, South Africa, provide valuable services for city residents. Waterways supply freshwater from nearby Table Mountain, regulate waterflow, improve water quality, support biodiversity, and are popular areas for recreation, tourism, and fishing.

However, urban development, change in land use, and pollution have degraded and polluted the city’s waterways, limiting its ability to regulate and supply water. Climate change has also led to greater rainfall variability, with both drought and flooding projected to worsen.

As a result, the city has developed its Water Strategy, aiming to become a water-sensitive city by 2040, as well as a Green Infrastructure Programme and a Livable Urban Waterway Programme (LUW). Through the LUW Programme, Cape Town is rehabilitating waterways and their catchments across the city, using water-sensitive design and nature-based solutions.

The study area for this project lies in two adjacent catchments of the LUW Programme, the Diep/Sand River and Zeekoe catchments. Our report analyzes the socioeconomic and environmental impacts of the sought interventions. Namely, creating retention ponds, extending and establishing wetlands, setting up community gardens and educational areas, designing and upgrading walkways, installing litter traps, revegetating and landscaping riverbanks, removing invasive plant species and replacing them with appropriate indigenous alternatives. 

Working with our partners, C40 Cities Finance Facility, and the City of Cape Town, we assessed two potential futures: a no action/business-as-usual scenario, and a scenario in which the nature-based infrastructure interventions are implemented. This will help communities and decision-makers understand the social, ecological and economic consequences of continued ecosystem deterioration, and show the value of investing in NBI. 

The results show that NBI interventions generate significant net benefits compared to the business-as-usual scenario, in which the ecosystems continue to degrade. 

We found that in the Diep/Sand river catchment, for every 1 South African Rand (ZAR) invested in the NBI, about 2 ZAR could be returned over a 25-year period, amounting to net benefits of ZAR 121 million from avoided costs and added environmental, social, and economic benefits. Among other things, the NBI reduces flood damages, avoid impacts of ecosystem deterioration on tourism and properties, creates jobs, and avoids the costly dredging of lakes. 

Similarly, in the Zeekoe river catchment, every 1 ZAR invested in NBI can yield ZAR 1.56 in benefits for society, amounting to net benefits of about ZAR 68 million of 25 years when using an 8% discount rate and an optimistic climate scenario with relatively little floods. 

We analyzed the performance of the NBI under different climate change scenarios and found that the NBI is particularly valuable under pessimistic climate scenarios with high avoided flood damages. The study also demonstrates that the NBI interventions benefit local communities by creating jobs and preserving valuable ecosystems, and spare the city of Cape Town from large spending on grey infrastructure.