Picture: Photo: EMER-G-MED.

Johannesburg - The owners the 150 cars damaged in the flash floods on the N3 highway will not be compensated by the City because it "was an act of God".

Last week on Wednesday about 150 cars were damaged after they were submerged in water along the N3 highway near OR Tambo International Airport.

Johannesburg Metro Police spokesperson Wayne Minaar on Monday said: "The owners of the cars towed their cars and there is nothing the city can do because it was a natural cause".

The severe weather conditions have reportedly killed at least eight people across Gauteng, including a six-month pregnant motorist who died after her car was swept away by the raging waters. Her body was recovered on from the Jukskei river on Saturday.

“Once in a century occurrence”

Sanral's bridge network manager Edwin Kruger said that the flash floods were a "once-in-100-years occurrence." The freeways would have, in the past, been designed to pass a 1:20 year flood or up to a 1:50 year flood in the case of larger rivers.

"This means that in any year, there is a 5 percent chance that a flood of this magnitude or greater will occur if the design recurrence period is 20 years. The design standards used in South Africa are similar to the varying international norms," he said.

Unconfirmed reports indicate the storm was indeed severe, with between 90mm and 150mm of rain falling in a very short period, according to Kruger.

Floods were not isolated events, and could occur within days of each other, depending on the type of storm encountered. It was not possible to guarantee that a road or bridge would never be damaged or over-topped.

"Unfortunately, due to the possible effects of global warming, this means that ever-increasing extreme events and some flooding of roads can be periodically expected.

"After a severe storm, there is potential for soil erosion (commonly known as scour damage) or sinkholes opening up, and these are closely monitored by the roads agency's routine maintenance contractors."

Roads not built to manage floods

The blocking of storm water pipes, culverts and bridges by homeless people was also increasingly becoming a problem. Although they were removed regularly, the illegal structures blocking the storm water systems were often reconstructed within a day or two of their being removed.

The Gauteng freeway network was constructed 40 years ago. Since then, the landscape had changed from predominantly agricultural land to developed land. Water absorption of agricultural land was higher than in built-up areas, as grass and soil absorb water while asphalt and concrete do not.

In addition, when drainage systems in built-up areas, not on the road network, failed - they were not built to manage floods - the run-off would increase and build up in low-lying areas like Gillooly's.

More flooding could be on the way

The Institute of Risk Management South Africa has urged South Africans to prepare themselves for extreme wet weather conditions, including possible floods, until February next year.

IRMSA chief risk adviser Michael Ferendinos said weather patterns characteristic of La Niña were expected to occur from December until February 2017, and will be accompanied by extreme wet weather conditions and possible floods.

It should be noted, Ferendinos said, that areas heavily affected by the drought could be exposed the most to flash flooding by being unprepared for high volumes of water.

ANA & The Star

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