Ecosystem-based adaptation of urban hydrology to climate change in three South African cities

Abstract

There can be no doubt that the world is experiencing climate change. Urban areas suffer intensified impacts thereof, including floods, severe storms, droughts and heat waves. Urban populations are increasing exponentially, forcing local governments to investigate functional, alternate ways to adapt cities to the negative risks of climate change, thereby becoming more resilient and ultimately suffering less catastrophe. Conventional hard infrastructure methods have proven to be insufficient against the impact of climate change. A method which has been considered positively is Ecosystem-based Adaptation (EbA), which makes use of natural processes, including biodiversity and ecosystem services (the benefits people derive from nature), to assist people in adapting to the adverse effects of climate change. EbA actions identified in literature range from maintaining rivers and wetlands to promoting natural vegetation. This dissertation aimed to critically explore the practice and presence of EbA within the climate change adaptation plans of three cities in South Africa (also referred to as metropolitan municipalities), namely: Cape Town, Durban and Johannesburg. The assessment of the adaptation plans was further supported by semi-structured interviews conducted with city officials and experts in the field. High-level water balances were calculated for these cities, so that the potential of EbA to contribute to reducing the vulnerability of urban water systems to the negative effects of climate change could be critically examined. The water balances were also used to identify the different types of water related infrastructure, either ‘soft’ (also called ‘green’ - e.g. wetlands, parks, rivers) or ‘hard’ ( also called ‘grey’ - e.g. storm water drains, sewers, roads). I found that the inclusion of EbA related solutions within the adaptation plans was sparse, often only vaguely making reference to EbA through ecosystem services or soft infrastructure. There is uncertainty as to whether the implemented EbA actions, were in fact implemented with EbA as the driver, or if they were merely projects undertaken for other reasons, rebranded as EbA. Determining the proportion of the water balance managed by soft infrastructure, proved difficult, due to the challenges in defining and categorising the different components of the water balance as either hard or soft. It was noted however, that rainfall was the main quantitative contributor to the all three of the cities’ water balance. EbA methods to manage a future reduction in rainfall include maintaining green spaces by growing drought resistant plants, and managed aquifer recharge. EbA methods to manage too much rainfall (for instance, floods resulting from increased rainfall intensity) include maintaining rivers and wetlands through river clean-up programmes to remove litter and alien vegetation. The suggestion that the resilience of urban water management can be supported by soft infrastructure using EbA approaches receives quantitative support from this study, since the natural water flows are of similar magnitude to the manages ‘hard’ infrastructure flows, but are currently only partially considered in the urban adaptation plans. However, the uncritical championing of EbA as a sole or dominant solution is premature. Further research is required into the efficacy of EbA actions in managing urban water.