Statistical “Events”

We’ve had significant flooding in the area twice in the last 10 years of so.

Back in 1996 there was significant flooding in the area. At the time it was declared, depending on where you lived, as a “100 year flood” or a “thousand year flood”. Out in Vernonia, I guess each was referred to as a “500 year flood”.

We also had significant flooding in 2007.

Side Note: All of this presumes a wealth of historical data which I think is suspect to begin with. I realize that we can find indications in historical data to predict some events, but given that our insight in to the weather of 500 years ago in the Northwest is pretty limited, I have to be a bit wary of the putting much weight on it.

Statistically, if you buy a 1:500 chance of something happening, the odds of it happening back to back are 1:250000 or one in a quarter million. I realize it’s not quite that since it’s been 10 years between 1996 and 2007, but the number is big. And yet it happened.

Could it be a statistical anomaly? Sure. We could go another 10,000 years and not have it happen, but I’m not holding my breath.

Whether you believe in Global Warming or not. Whether you believe this is a cycle influenced by humans or not, things seem to be changing in the weather. Even our current administration finally had to acknowledge the changes, if not agree on the source.

In that case, I wonder how often such determinations as “one in a 100/500/1000” are recalculated?

If it happens again in less than 10 years, then do the experts say “yeah, 3 times in 20 years would seem to indicate our estimates are a bit off. Or does it only take two times?

I’m sure there are people trying to figure this out right now. Surely people who sell flood insurance are going to be going over the data. Two “events” that were supposed to be 1:500 in 10 years has really got to put a kink in their bottom line, I would think.

And I can only image that it will really be a bad thing for people who were purchasing flood insurance based on data indicating they were only at risk once in five hundred years suddenly have their rates spike when the insurance companies change their estimates and declare it to be a much higher risk. Potentially a higher enough risk to make flood protection prohibitive.

What a terrible thing to have to deal with on top of potentially losing much of their possessions, to then have to look at either paying a significantly increased premium or, even worse, having to sell, perhaps at a reduced value, because of the now increased risk of flooding.

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