Facing rapid urbanization and climate change, African cities need to find solutions to enhance their resilience. Sustainable urban drainage systems (SUDS) are in this regard a viable solution to address projected climate change impacts and existing deficits in African cities’ drainage infrastructure.
In an article published in Natural Hazards, Mguni, Herslund and Bergen Jensen examine the potential for SUDS in African cities. They argue that conventional pipe-based stormwater management systems, whose “main purpose is the rapid removal of all stormwater for the urban landscape” (p:3), have been shown to have undesirable effects on the urban environments. Their effectiveness as a flood management strategy has particularly been critiqued.
Instead, SUDS rely on green elements such as green roofs or rain gardens, and depend on hydrological processes of infiltration, evaporation, conveyance and retention of stormwater. Some SSA cities like Johannesburg and Dar es Salaam have already experimented with such systems.
In the article, the authors conduct a SWOT analysis of the theoretical potential of SUDS in SSA cities. They give a comprehensive vision of the value and function of these systems and compare them to more conventional drainage systems.
SUDS’ main strength lies probably in their contribution to flood hazard mitigation by “reducing and/or delaying surface run-off through storage in the ground or elsewhere, thus ensuring lower flood peaks” (p :8). SUDS also present a more holistic way of addressing urban water issues. In Dar Es Salaam, a UNEP report from 2005 estimates that the city had the “possibility of harvesting over 5,000,000 m3 of water per year from buildings alone” (p:10).
As weaknesses, the authors note that SUDS require high levels of coordination between actors, and high levels of maintenance. It is also relative difficult to quantify the effects of SUDS, especially at a large scale. This, they say, has the potential to hinder the liability of SUDS as a policy alternative. Besides, with regard to water issues, storm water management issues remain in general less prioritized than water supply and sanitation.
With the possibility to augment water supply but also respond to issues of water quality and biodiversity, SUDS ought to be favoured by African cities in their water strategies. SUDS can also be a way to support urban and peri-urban agriculture. However, their adoption should be carefully considered and adapted to contexts since water issues, more than others, require beyond their technical aspects a keen understanding of the “socio political, institutional and biophysical contexts of the area in which they are to be implemented” (p:5).
Photo: Drain in Kalibari community. Ashley Wheaton (wikimedia).
|Author(s)||Patience Mguni, Lise Herslund, Marina Bergen Jensen|