Friday, 4 January 2013

A Barrier to Logic

I must be missing something in this report on the engineer who wants a new and improved Thames Barrier.

Engineers are, of course, intelligent and yet fundamentally simple folk. They see a situation in quite a binary manner. There could be a flood, therefore there should be a better barrier, is Dr Bloore's attitude. Normally I'd write that off as one of those charming One-or-Zero attitudes from an engineer, and ignore him.

But it's the report from the Environment Agency that worried me:

"It also said major changes including a new barrier were unlikely until 2070 as a one-in-1,000-year flood would not occur until then."
Or is it just me?

There are 53 years until 2070. That's not 1,000 years. But that's not how one-in-1,000 works. That says to me that, ignoring back-loading of risks due to global warming (and they seem to be ignoring that anyway) there's a slightly more than 5% risk of a one-in-1000 year flood. Or to put it another way - if the value of damage to London of a one-in-1000 year flood is 20 times more than the cost of an improved barrier, then we ought to get on with the barrier.

I reckon we need a bigger barrier.

5 comments :

  1. We in Europe's Valley of the Kings* (or Jersey as you know it) understood a while back that million-to-one chances generally occur about nine times out of ten. Snow is supposed to happen once in about twenty years - we had have enough snowfall for the island to grind to a standstill three times in fifteen months.

    * This is not a joke.

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  2. "Engineers are, of course, intelligent and yet fundamentally simple folk. They see a situation in quite a binary manner."
    Yes I do!

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