A Once in 50 years Incident?

It seems to me that quite a number of people do not understand what probability means in the recent flood. Due to the very successful flood alleviation programme instituted by the Public Utilities Board of Singapore, the flood areas in Singapore have been reduced drastically over the years so that the public in Singapore has become accustomed to flood free situation despite living on a low lying, increasingly built up tropical island. However, in the last month, there have been flash floods on three occasions in low-lying areas of Singapore including the famed Orchard Road, around the Scotts Road junction.

Horror of horrors, are we living in *third world* country?

The reaction of the public would be amusing if it did not betray such innocence of probability let alone other physical and economic factors. When the public is told, this is a "Once in 50 years event" what they do not seem to recognise is that this is a probability. In other words, there is a one in 50 chance of such a flood occurring in the same way that if one flips a coin, there is a 50% chance it can turn up heads but it could easily be flipped 100 times and still be heads all times and that still does not change the truth of the original statement that there is a 50% chance of it being heads although of course that is certainly a rare series of events.

As a bunch of engineers, generally excellent at what they do, PUB engineers forget that the general level of understanding of simple probability, let alone an understanding of engineering, rainfall, tides, permeable versus impermeable surfaces and a low lying island, is sorely lacking. So perhaps what is needed in this case is for engineers to improve their ability to communicate with the public in simpler terms. Idiot-proof explanations are needed and any comments relating to probability should be avoided.

Good luck engineers and don't forget you can always hire a spin doctor but make sure your spin doctor understands some rudimentary engineering and probability and has a good dose of common sense.