The heavy rainfall and flash floods on 9 November was an act of God, and beyond the capacity of the City of Johannesburg’s stormwater systems.
This according to the Johannesburg Road Agency’s Managing Director of, Dr Sean Phillips.
The agency started assessing the damage to infrastructure the following day, cleared debris, silt and other obstructions to roads, bridges and stormwater drainage systems. A number of bridges were reported flooded or collapsed and more heavy rain forecast for the weekend.
Phillips said the ‘City’s road infrastructure is not designed for severe flash floods and that isolated flooding is bound to occur. Despite this, the agency was aware of blocked drains. Phillips emphasised that maintenance and repairs to damaged stormwater drains and blocked stormwater drains have been prioritised.
“A road is designed for the likelihood of the severity of the storm statistically happening once every five years. The road surface and reserve including the stormwater servitude is designed to act as a channel if the underground system reaches capacity. Furthermore, major underground drainage systems including crossings through residential properties are designed for storms statistically happening once every 25 years,” Phillips added.
The City’s rivers however have either 1:50 year or 1:100 year floodlines and buildings cannot be erected below these floodlines as regulated by the Water Act, Phillips said.
“To build infrastructure that can handle a 1:100 year storm would be too expensive. It would be too expensive to maintain as well,” Peters-Scheepers said.
As on the morning of 10 November, the agency identified damaged roads, bridges and stormwater drains, some of which where still closed on 11 November, as:
– R55 in Kyalami bridge collapsed
– Linksfield Road, off-ramp and on ramp to N3.
– Corner Lousie Botha and Houghton Drive near Sasol, collapsed wall.
– Siyabusa (Rabie Ridge), flooding due to insufficient stormwater system capacity
– Joburg Zoo wall collapsed next to Jan Smuts.
– M1 South Athol Oaklands, and Oxford area debris to be removed.
– Low lying bridges such as John Nhlanhla bridge, Buccleuch bridge, Modderfontein and Pretoria bridge, and bridges between Kyalami and Dairnfern have been severely damaged.
“JRA has duly inspected recurring blockages in the areas which are termed as flooding hotspots and we are monitoring low level bridges prone to overtopping during heavy downpour.
“Motorists are urged to obey road signs, traffic signals and especially road closures due to flooded bridges or unsafe driving conditions which are unsafe to traverse. In the event of a flash flood, or where residents are at risk, it is advisable to immediately evacuate the area and seek a place of safety,” Phillips said.
Residents and road users are encouraged to report all road and storm related emergencies to 0860 562 874, email hotline@jra.org.za /or tweet @MyJra or download the JRA Find&Fix mobile app.
Traffic lights throughout Joburg have been affected since the storm. Phillip said that by the end of Thursday the agency had addressed 71 of the 108 traffic light faults.
