Even if the U.S. Army Corps of Engineers had released water at record levels from Gavins Point Dam for 365 consecutive days, it wouldn't have been enough to prevent serious flooding on the Missouri River in 2011.
That was one of the findings in an analysis the corps released on Friday about possible adjustments in flood control storage.
The size of the 2011 challenge begins with the 61 million acre feet of runoff in the basin, said Brig. Gen. John McMahon, commander of the corps' Northwest Division and a key figure in the operation of Gavins Point and five other main-stem dams.
In calculating how long it takes to move that much water, said McMahon, "you come up with every second of every day for 365 days you'd have to pass 83,500 cubic feet."
That compares to the previous record release from Gavins Point of 70,000 cubic feet per second. And since releases must be held to 30,000 cubic feet through the winter months because of ice, water would have to move at a rate of about 100,000 cubic feet per second for the other nine months.
"The takeaway from the report is that what we have here in the Missouri River Basin and the Missouri River system is a volume problem," McMahon said. "And what I mean by that is what comes into the system must go out of the system every year."
The corps' analysis came in response to a recommendation from an independent review panel that the river-management agency hired last year.
The review panel itself said in December that the worst flooding on the Missouri since the dams were installed was largely the result of unforeseeable weather circumstances, including heavy snow, rapid melting and heavy rain in eastern Montana and western North Dakota.
The resulting deluge closed Interstate 29 along the Iowa-Nebraska border, Interstate 680 in Omaha, and Iowa Highway 2 near Nebraska City. It destroyed farmsteads, buried thousands of acres of farmland in sand, and inflicted tens of millions of dollars of damage on levees.
In expanding on its Friday assessment, McMahon and Jody Farhat, chief of the water management division at Omaha, said increasing the combined 16.3 million acre feet of flood storage would come at the expense of navigation, power generation, recreation and other management priorities.
"Flood control is the only authorized purpose that requires empty space in the reservoirs," said the executive summary of the almost 50-page report, "therefore, the other authorized purposes, all of which require water-in-storage to maximize benefits, would experience negative impacts with additional flood control storage."
"What we've got to do here is take a system approach," McMahon said. "The reallocation of reservoir space by itself will not solve the problem."
Even if the corps freed up as much as 4.6 million acre feet of additional flood storage -- more than the combined capacity of Lewis and Clark Lake behind Gavins Point Dam and Lake McConaughy in Nebraska -- 2011 flooding would still have been extensive.
Even with that much more cushion, "2011 would have been a historic flood with releases nearly 1.5 times the previous record and catastrophic damage from Montana to Missouri."
And with the clear exception of 2011, according to the corps analysis, the economic gain in other years would typically be outweighed by the cost of lost power production and other river benefits.
That doesn't mean that McMahon is ready to stick with the status quo.
"The sad truth is that we will have another event, maybe not in our lifetime," he said, "and now is the time to marshal the will and resources to do something about it, so we don't have a repeat of events of 2011."
One option would be to widen the river channel south of Gavins Point by moving levees farther back from the channel.
"We're going to have to change the way the flood plain is viewed," he said, "and this is an all-levels-of-government proposition."
Reach Art Hovey at 402-473-7223 or at firstname.lastname@example.org