Report: Corps Handled 2011 Missouri River Flood In Accordance With Mandates

The Prairie Fire, which aspires to be the progressive voice of the Great Plains, has posted an analysis of the 2011 Missouri River flood and concludes that the Corps handled the historic event in accordance with its Master Manual. The report also dispels rumors that the protection of least terns, piping plovers or pallid sturgeon played any role in regulating the waterway.

While some people may see the word “progressive” and automatically discount this publication, I think it would be a mistake to do so. The information in their analysis correlates with what I’ve seen and reported this summer. The fact is, this was a 500-year flood event, and there was very little leeway in how it could be handled.

Like everyone else, I’m awaiting the results of future investigations and inquiries that will be held regarding the flood, but based on the information we have now, this looks like a pretty good summary.

I’ve posted Prairie Fire‘s conclusions below. Read the entire report here.

  1. Prior to May 1 we believe the system had been operated exactly as dictated by the conditions which occurred throughout the basin during spring and according to the Master Manual. Because of the heavier than normal plains snowpack which had been stored in the reservoirs and the higher than normal Rocky Mountain snowpack, most of which accumulated during April, estimated at 141 and 136% of normal, the USACE began increasing system releases on April 8. System releases were increased from 21,000 to 45,100 cfs by the end of April despite the fact that the state of Missouri was in the midst of the 5th wettest April on record and that there was already flooding occurring at Nebraska City.
  2. After May 1 we believe that the Missouri River mainstem reservoir system was operated again in accordance with the Master Manual in response to the abnormal precipitation events that kept occurring. With the expectation that the abnormal precipitation patterns would stop, the system was operated to maximize flood risk reduction. During May the Missouri River mainstem reservoir system was used to store as much runoff as possible and despite the abnormal amount of runoff there was limited flooding during May and the system still had 16% of its total flood storage available at the end of the month. Although by May 29 the USACE was predicting releases of 150,000 cfs by mid June, by storing this record runoff, the USACE was able to keep system releases below the previous record of 70,000 until May 29. We believe that the USACE choose a release of 70,000 cfs based on this previous experience, knowing that this release would cause minimal impacts while maximizing the time available for emergency flood protection activities. In order to minimize the maximum flood heights, the USACE ended up using nearly 100% of the flood storage available in the system by the end of June.
  3. The construction of chutes, backwaters, emergent sandbars and shallow water habitat have not contributed to the flood but in most cases actually increased flood storage capacity of the system resulting in reduced flood heights.
  4. We found no evidence that any management actions were taken for least terns, piping plovers or pallid sturgeon during 2011. When enacted, all fish and wildlife management actions for least terns, piping plovers or pallid sturgeon are dependent on water supply and not on the storage of water for those actions. All scheduled actions were cancelled due to the record runoff and therefore did not contribute to the magnitude, timing or duration of the flood.

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