Time to build my own Ark!

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revman

New member
John,

I live just south of Owatonna, MN, and you should see the rain we are getting. Most homes are flooded and streets look like rivers. This is almost as bad as September, 2005 when we got between 13-15 inches.

So the obvious question is, since those are supposed to be "100 year floods," is my time keeping device off a little? Is this just a pattern that we're stuck in?

It's crazy!

REVman
 
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doospunk

Active member
Man - Sorry to hear that! I'm just north of the cities, and my wife said she heard the metro was supposed to get 3-4 inches through tomorrow, though I know they are calling for the worse to occur down in the southern part of the state. Hope everyone down there is safe.
 
bearrassler

bearrassler

Well-known member
We have been getting quite a bit of rain in ND but nothing like southern MN. I am in my 50's and have been through a 250 year flood and a few 100 year floods. The weather service explained to us that a 100 year flood means that there is a 1 in 100 chance of a 100 year flood every year. It is possible to have 3 100 year floods in 3 years if that makes any sense. I hope you all stay safe down there.
 
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slimcake

Active member
I live is SE MN and luckily most of the rain went just north of me today. I had 4.3 inches from about 10 last night till 8 this morning. Just a couple of weeks ago we had 3 inches one night and then 2 nights later got 5 inches in about 3-4 hours.... I remember the floods of 08 when we saw 19 inches in a 24 hour period. That was the wildest night of my life. Thats a whole different story though.... What is the deal with this pattern of 100/300 year floods??
 
jd

jd

Administrator
Staff member
I guess first off, I think the use of the term "100 year flood" is dumb. All it does is confuse folks or add to the lack of trust in forecasters when a 100 year flood happens more than once in less than 100 years.

bearrassler is right that it does not mean that the type of rain event in a 100 year flood will ONLY happen once in 100 years, but rather there are certain odds that the event will happen in 100 years. Of course the mention of the odds usually seems to be left out of the term. Not sure if it's the mindless media's fault, or others, but like I say, just a dumb term to use. But what the heck, it's a nice catch phrase and headline maker and that is just what the media likes. No reason to actually report things correctly.

-John
 
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chadlyt

Member
It's amazing the amount of rain we have recivied his summer, and now this. I'm in SEMN also and this is now our 2nd 100 year flood in 3 years.

I am starting to feel old.
 
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chadlyt

Member
well, for the folks that received 10+ inches of rain...that would cover the yearly snowfall for them if it fell as snow...plus 20"....

One thing i do hope, is that this type of system comes back through a few times during the winter...
 
xsledder

xsledder

Active member
Administrator said:
I guess first off, I think the use of the term "100 year flood" is dumb. All it does is confuse folks or add to the lack of trust in forecasters when a 100 year flood happens more than once in less than 100 years.

bearrassler is right that it does not mean that the type of rain event in a 100 year flood will ONLY happen once in 100 years, but rather there are certain odds that the event will happen in 100 years. Of course the mention of the odds usually seems to be left out of the term. Not sure if it's the mindless media's fault, or others, but like I say, just a dumb term to use. But what the heck, it's a nice catch phrase and headline maker and that is just what the media likes. No reason to actually report things correctly.

-John
Click to expand...

It’s the engineers who are responsible for coining the phrase “100 year storm.” It is a lot easier to say then 7.58 inches in 24 hours duration. Lately we have been using the term “Base Flood Event” or “BFE” (and I thought BFE meant something else) to avoid the confusion.
“100 year storm” doesn’t mean a storm once in a hundred years like bearrassler and John both said. You can have one, two or more “100 year storm” in the same year. It is the probability (1% chance in a given year) that a storm with a given amount of rainfall happens within a specific duration. For northeast Illinois a “100 year storm” could be 0.91 inches in 5 minutes, 3.56 inches in an hour, or 7.58 inches in 24 hours. (Adjustments have to be made for Chicago and time of year.)
What is funny about all this information is that it is based on 83 year of data; so I pose this question “How can we know what a 100 year storm is if we only have 83 years of data?” There are rumblings that the data is being updated to reflect the last 20-30 years of storms, and we’re changing the term for storms.
 
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