HELENA, Mont. (AP) -- The U.S. Army Corps of Engineers did what it could with the record flooding on the Missouri River this year although proposed changes could help avoid a disastrous repeat, especially since such floods could become more frequent, an expert panel said in a report released Tuesday.
The 99-page analysis said "climatic extremes" appear to be getting "bigger and more frequent," with the experts calling for updated flood probability models and procedures. It did not cite climate change as a factor, saying the issue was "beyond the scope of this report."
The corps has said that the floods caused $630 million in damage to the levees, dams and channels built to control the river. The corps manages the 2,341-mile-long river, which flows from Montana through North Dakota, South Dakota, Nebraska, Kansas, Iowa and Missouri.
The report said the 2011 flood was the "the largest of the period of record in terms of runoff volume, and it stressed the mainstream reservoir system and its operators as never before. Many people were dismayed that such a damaging event could occur, in spite of the flood control reservoir system."
An expert from the panel said May rainfall in Montana exceeded 300 percent of normal, surprising everyone and causing the biggest problems. But he said such unusual weather may be a more common part of the weather cycle, no matter the cause.
"Back when they designed this master manual, it was a weather event that they probably just didn't think was possible," said Bill Lawrence, a hydrologist with the National Weather Service in Tulsa, Okla. "I think whether or not you believe in climate change is beside the point."
The experts waded cautiously into the debate over whether the corps should release more water from upstream reservoirs in order to leave more room for floodwater storage. This past season, the corps was forced to release water from the full reservoirs knowing it would cause downstream flooding.
"The unprecedented inflow volume tested the reservoir system more than ever before," the report said. "The panel recommends a review of the system storage allocations, to include the flood-control storage needed for floods like 2011 or larger."
The corps is required to keep water in the upstream reservoirs as it manages the river for eight competing uses: flood control, irrigation, navigation, hydroelectric power generation, water supply, water quality, recreation, and fish and wildlife enhancement.
Flood control requires leaving reservoirs as empty as possible, while the other uses require that water be kept in the reservoirs, corps Brig. Gen. John McMahon said Tuesday. He promised a "flexible approach" as the corps considers reducing reservoir levels -- knowing it will harm the other uses.
Montana Gov. Brian Schweitzer has sparred with downstream governors, who want reservoir levels in his state reduced in order to provide more room for floodwater. Schweitzer has said such a policy would hurt Montana recreation and agriculture in dry years.
The experts said their first recommendation would be to ensure more federal money is available to properly repair and maintain the current system of spillways, tunnels and other infrastructure.
Other recommendations included improved monitoring of pending snowmelt in plains states, such as is done in the northern Rocky Mountain that feed the river.
They also suggested better collaboration with weather forecasting and water monitoring agencies, improved monitoring systems for tributaries, and an update of the master manual that guides management for all authorized uses on the river.
"The panel found that the decisions of the corps were appropriate and in line with the appropriate manuals, but both the manuals and the decision-making process can be improved," the experts said. "During extreme flood events, such as in 2011, the master manual does not provide a workable formula for operational decisions and during extraordinary flooding experience-based judgment along with repetitive quantitative analysis must be used."