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Published March 21, 2012, 07:09 PM

FEMA, Army Corps disagree over 100 year flood levels

Fargo, ND (WDAY TV) - As meetings between the Diversion Authority and communities affected by it continue there is some disagreement and confusion about what a 100 year flood is. The Army Corps and FEMA are feet apart and disagree over how often water would need to be stored south of the metro during a flood.

As meetings between the Diversion Authority and communities affected by it continue there is some disagreement and confusion about what a 100 year flood is. The Army Corps and FEMA are feet apart and disagree over how often water would need to be stored south of the metro during a flood.

Eric Dodd – F-M Diversion Authority: “People have lived through what they experience what is a 100 year flood event back in 97 and 2009 and probably prior to that as well"

If you’re looking for what the official definition of a 100 year flood it will vary depending on which agency you go to. FEMA's current 100 year level is 38.5 feet. That's expected to go to 39.5 feet when new flood maps come out. Under the Army Corps of Engineers numbers, the flood of record from 2009 is now just a 50 year event. The 100 year level is at 42.4 feet.

Eric Dodd: “The change in hydrology has led to the change in what is a 100 year flood.”

The main difference in the numbers comes from the year looked at. FEMA averages all the years prior to 2002, while the Army Corps uses 1942 to 2010.

This means the very dry years of the 1930's get figured into the FEMA number skewing river levels lower and in addition the extremely wet years of the last decade are not included in FEMAS calculation while the Army Corps do and that would increase average flow and flood levels on the Red.

Eric Dodd: “So this mystery 100 year flood has not yet happened, but yet recognize that 100 year floods do happen across the country, 500 year floods happen in Bismarck, Minot, Nashville, Cedar Rapids and elsewhere.”

In Fargo-Moorhead the new 500 year level would be at 46.7 feet. The FEMA and Corps number are still preliminary and both agencies hope to have final numbers by the end of the year.

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