Sustainable Asset Valuation (SAVi) of Stormwater Infrastructure Solutions in Johannesburg, South Africa

Over the life cycle of the infrastructure, the hybrid solution and the full renaturalization of the stream are the most cost-effective investments. Grey stormwater infrastructure requires the highest upfront investment, while annual operations and maintenance costs are higher for the renaturalized stream.

The hybrid solution and renaturalized stream provide additional benefits, some of which the grey stormwater infrastructure, by design, cannot provide. Among these benefits are improved flood mitigation resulting in avoided costs of flood damages, additional employment from landscaping, and environmental benefits such as carbon sequestration and additional water supply. The avoided cost of flood damages is by far the largest additional benefit of the nature-based stormwater infrastructure.

Under different climate change scenarios, the case for nature-based infrastructure options becomes even clearer: the more volatile precipitation patterns become, the larger the benefits in comparison with a grey built solution. Indeed, a grey stormwater solution's capacity is limited by design and therefore less equipped to deal with extreme weather events. This also illustrates the importance of using climate parameters when assessing the costs and benefits of different infrastructure options.