Major storm as cloudburst occurs over Krugersdorp
Thunderstorms have also been reported in the area.
Arrive Alive has warned road users to drive extra carefully after a major rainstorm hit Krugersdorp at about 3.30pm today, 2 March.
They said that roads in the area could become flooded as the cloud burst caused a lot of rain to fall in a short amount of time. Thunderstorms have also been reported in the area.
They listed the dangers of flowing water over roads and low water bridges as follows:
• Flowing water applies pressure to contact areas. The higher the speed the higher, the pressure.
• With water that is one meter high it will flow out at a speed of 4,47 meters per second or 16 km/h. The pressure is one metric tonne per square meter.
• With a wheel half under water the area is 0,4 sq m and the force 0.4 tonne per wheel. For the four wheels it becomes one and a half tonnes and for 2m of water it becomes 2 tonnes per sq m.
• Be careful, water that has fallen only 0,4m reaches a speed of 3,2 km/h and can sweep your car off a road bridge.
When the side of the body of a vehicle makes contact with the water the force increases rapidly but the water now also acts on the underside of the vehicle as well and starts to lift it. It is now able to float like a ship. The weight of the vehicle will not be able to hold it on the road. Every cubic meter of space in a vehicle can lift one tonne.
Be careful, 0.6 meters of water can float a car. Only vehicles that are open and let the water through will behave differently.
Establish the body area of the vehicle and its mass. From this, calculate the how deep the vehicle will sink in the water before it floats. For a truck that is 8.5 metres long and 2.5 metres wide, with a mass of 12 tonne it will float at a level of 0,532 meters above the body base and be able to float down the river.
Read more here
Flash floods – what you need to know
Flood water leaves man trapped on roof
