Why Johannesburg Was Not Equipped For Flashfloods

3 Jan

Last November 9, the city of Johannesburg suffered from heavy rainfall and flashfloods that is beyond the capacity of the storm water systems. On the morning of November 10, people woke up to damaged roads, bridges and storm water drains. Siyabusa (Rabie Ridge) was flooded because the storm water drains were insufficient to handle the large amounts of water.

The Johannesburg Road Agency assessed infrastructure damages the following day and revealed that the city’s road infrastructure was not capable of handling the severity of the flashfloods. This resulted into isolated flooding. The agency was actually aware of the blocked drains and maintenance and repairs to the damages are being prioritized.

However, the roads were not designed for a severe storm with heavy rainfall that statistically happens at least once every five years. The road surface including the reserve and the storm water servitude only acts as a channel if the underground system has reached its capacity. Furthermore, the underground drainage systems including the crossings to residential homes were designed to handle storms that will statistically happen every 25 years. The city’s rivers have either a 1:50 or 1:100 yearly flood lines which are regulated by the Water Act. Buildings cannot be constructed below these flood lines.

Building an infrastructure that can handle a 1:100 year storm will require a very large investment. It is also too expensive to maintain. Recurring blockages on the storm water drains have been inspected and have been identified as flooding hot spots. Low level bridges that are prone to overtopping when there is an extremely heavy rainfall are also being monitored.

The bridges that were flooded were temporarily closed because they are unsafe for motorists. Residents who are at risk during a flashflood are advised to immediately vacate their homes and look for a safer place to stay.

When drains are not regularly inspected and maintained, it can cause more serious problems. Commercial and residential drain clearing is available to prevent blockages from happening in the future. When the drains are unblocked and cleared, you can sleep peacefully at night knowing that one potential problem has been solved.