City Hall Fortune Tellers At It Again

CIty Manager Claims 15% Chance Of Disaster

Do you remember last November when city hall first told us how costly replacement of the dams would be and how dangerous they were? At that time the claim was 40% chance of failure in 50 years.

That sounds pretty convincing, seems like with that high a probability the dams will fail and all those people will die, we should eliminate the risk. Right?

But wait just a minute, doesn't a 40% or 15% chance of an event happening in 50 years mean it also has a 40% or 15% chance of happening in the next 5 minutes, given the next 5 minutes does happen in the next 50 years?

Trying to understand the 'science' behind these predictions I had long email discussion with Mr. Sims from the city and he finally explained the numbers this way:

Between 10% and 40% probability in the next 50 years. This is more like saying there is between a 1 in 475 and 1 in 100 chance in any given year.

If 10% - 40% probability in the next 50 years is like saying a 1 in 475 and a 1 in 100 chance in any given year that equates into a .25% - 1% chance in any given year. Hardly seeming like the kind of probability of disaster that should be causing all this fuss.

I have asked Mr. Kenning to supply the methodology that arrives at the 15% chance in 50 years, and will be interested to hear all the other plans to mitigate against the disasters that will also hit the rest of Nanaimo.