Tuesday, June 23, 2009

The "100 Year Storm" Crock

Not to pick on the engineer from West Allis, but here's the quote:

"Our system is not designed to handle, nor any system is designed to handle, what is fairly close to a 100-year storm," said [Mike] Lewis, who met with [West Allis] residents Monday

That "100-year" line has been used a lot lately. And that phrase has an odor which strongly resembles the odor of the stuff in those West Allis basements.

Actually, the "100-year" line is used every year, sometimes twice a year, to explain why $Mega-Zillions of sewer systems, interceptors, and drains do NOT work as advertised.

It's always a "100-year storm" which is at fault.

That was the case 12 years ago when 9" of rain fell in a couple of days, flooding Brookfield and Elm Grove. That was ALSO the case exactly one year later, same time, same place, about the same amount.

That was ALSO the case last year during June, and THIS year during June.

Getting the picture? "100-year event" doesn't mean "100-years." It simply means that somebody decided to design and build an inadequate system and made up the "100-year event" label to justify that.


Billiam said...

Let us also remember that, with larger populations, and more reliance on high tech, events that wouldn't have rated much notice 50-100 years ago, now seem disastrous. Also, people are less able to fend for themselves. After all, Big Daddy Gummint' will take care of them.

Anonymous said...


A 100-year event does not mean it happens only once every 100 years.

Winston Smith said...

Actually, the 100-year flood is a probability. It implies that the storm has a 1 in 100, or 1% chance of occurring in any given year. A municipal system cannot be economically feasible if designed for the 1% event. Typically, it is designed for the 10-year event (or 10% probability of occurence) and the system is then checked for the 25-year event (or 4% probability) for overtopping.