OLEBOGENG MANHE | Modern drainage can transform informal settlements

A home is more than just a shelter. It’s a place where people can feel secure, healthy and dignified. It is the foundation for social equality, participation, work and education.

SA has made significant progress in developing informal settlements, but challenges remain. Flooding can have devastating consequences, especially for the most vulnerable, resulting in large-scale property damage, displacement, health risks from polluted drinking water and even loss of life.

As climate change is likely to make extreme weather events more frequent, government and private infrastructure developers must continue to seek innovative ways to address this issue.

Informal settlements generally form organically with little planning or control, whereafter the government assumes the responsibility to develop them further. Unfortunately, numerous informal settlements are established in dangerous regions, such as below flood lines.

During periods of heavy rainfall, rivers and streams can overflow their banks. Informal settlements also often lack the infrastructure to manage heavy rainfall and typically lack adequate drainage.

One solution is to construct or improve nearby flood detention ponds, designed to absorb excess water and slowly release it back into the environment. However, special care must be taken in the design and construction of these ponds, as they can fill up quickly and potentially overflow, worsening the flooding problem.

We often work with public partners to upgrade and modernise drainage infrastructure in existing informal settlements. Upgrading involves installing new drains, culverts and channels to help direct stormwater away from homes and other structures.

Incorporating modern drainage technologies and practice, such as constructing permeable pavements that allow water to seep through the surface and into the ground, can substantially help encourage runoff.

Similarly, bioswales – landscape elements designed to concentrate or remove silt and pollution from surface runoff water – can be used to naturally filter stormwater before it enters the drainage system and prevent clogging.

Rainwater harvesting systems can be installed at key locations to collect and store rainwater for later use. Vegetation also plays a critical role in how water is absorbed into the earth.

During rainfall, water is absorbed into the soil by plant roots and this helps prevent soil erosion. By constructing purpose-built rain gardens and encouraging and supporting homeowners to cultivate lawns, plant trees and flowerbeds outside their homes, we can significantly improve the capacity of residential areas to absorb rainwater, reduce runoff, and ultimately mitigate the risk of flooding.

Finally, participatory re-blocking is a more extreme measure that may cause fairly considerable disruption in the short term, but can help ensure long-term sustainability. This involves the reconstruction and rearrangement of informal homes that have sprung up. These are realigned in clusters, creating more open spaces in which municipalities can introduce the necessary infrastructure.

■ Manhe is chairman of the Gap Infrastructure Corporation