Water releases from the Garrison Dam will reach 150,000 feet per second by June 9 - more than double the amount that was being released a week ago – which will push the Missouri River in Bismarck to a depth of more than 20 feet by early June.
The new projections were announced Saturday during a public meeting at Bismarck City Hall. Flood projections have changed daily since the flood warnings first went out on Monday, and the estimates could change again depending on rainfall and runoff.
The Garrison Dam releases will be tempered because the river is flowing at such a fast pace that it has scoured the riverbed and has created greater capacity to hold water, according to local officials. By pushing sand and debris downriver, the river has created a deeper bottom.
“The river is flowing about seven or eight times faster than normal, which is eroding the channel and the banks in some cases,” said Maj. Gen. David Sprynczynatyk, adjutant general of the North Dakota National Guard.
At 150,000 cubic feet per second, the river would have been expected to reach a depth of about 22 feet in Bismarck, according to figures provided by Sprynczynatyk. Instead, because of the river’s increased capacity to hold water, the river is expected to reach a maximum depth of 20.6 feet.
As of Saturday afternoon, the releases from the dam were 80,000 cfs and the river was at a depth of 15.8 feet. Release rates will increase to 85,000 cfs by Monday, to 120,000 cfs by June 2, and then to 150,000 by June 9 and into July, said Todd Lindquist, who works for the U.S. Army Corps of Engineers.
Release rates may continue at 150,000 cfs until July, Lindquist said.
During the meeting, media and residents of Bismarck and Mandan questioned the government officials about the accuracy of the data, considering the estimates released to the public have changed so many times during the past week.
Almost everyone blamed the weather.
“Like I said, we are continuously updating those models,” Lindquist said. “What is really driving the changes is the recurring precipitation events that we’re seeing in the basin, primarily northern Wyoming, eastern Montana and the western Dakotas.”
After being asked repeatedly to outline a worst-case scenario so residents in flood zones can be prepared, Lindquist said the Corps has developed models to determine a range of scenarios. He said he’d try to get answers on that.
“It’s a very fair question. It’s consistent. That’s why the frustration has been compounded,” he said. “I will visit with our commander as well as our water management division and see if they can give us a worst-case figure. I doubt that they will be willing to do that because of a number of variables, but I will ask the question.”
Asked if the Corps had indicated to local officials early on that the flows might have to be increased to the point now projected, Bismarck Mayor John Warford said, “I can’t speak for the Corps.” When pressed further, he said now is not the proper time to point fingers or assign blame.
“We need to focus our energies on fighting this flood, rather than to try to find out if the Corps was withholding information,” he said.
Brian Bitner, chairman of the Burleigh County Commission, said local officials had to trust the Corps’ data in the beginning, but now engineers for local governments are working with the Corps to develop the projections.
“So it’s not just the Corps now that’s providing that information,” Bitner said.
Bitner later said the worst-case scenario would be to have to release water from the dam at the same rate that water was flowing into the reservoir. “If there’s 179,000 cubic feet of water per second coming into Sakakawea, the worst-case scenario is 179,000 cubic feet could come out,” he said.
Nonetheless, the river’s increased capacity to carry water gave public officials some relief after days of scrambling to oversee the construction of barriers, coordinate sandbag efforts and disseminate information to the public.
Bruce Strinden, chairman of the Morton County Commission, said the information public officials are getting now provides a more accurate, and in some ways more optimistic view of how the flood fight will play out.
“Many times, I’ve been very skeptical through this process of some of the information we have gotten,” he said. “And I have to admit to you that this was the first glint of optimism that I’ve felt,” regarding information that the increased flows were in large part offset by the river scouring.
Bismarck is continuing to build a levee system to protect areas of south Bismarck. City and county officials said they were confident they would have protections in place by the time the river reaches the estimated peak flow. The goal is to create the levees to a height of 20.6 feet, plus another foot for a buffer.
“I’m convinced that we will win this flood fight,” Warford said.
Meanwhile, Mandan has decided against an earlier plan to construct several dikes to protect the south and east sides of the residential area including Lakewood, Marina Bay and Harbor View. The Corps, Mandan Mayor Tim Helbling said, determined that groundwater would seep from one side of the dikes to the other regardless of whether the structures would be able to stop surface flooding.
“We were going to try to block off all of the channels into the three bays to try to alleviate groundwater,” Helbling said. “What they concluded was that if we put the levees in place, the water would equalize between the two points, so it wouldn’t do any good to do that.”
Helbling, though, was still upbeat. Even though some residential areas are projected to be underwater, he said the water might only be a few inches deep and, in that case, could be repelled by sandbagging.
“Please keep doing exactly what you’re doing,” he said. “I’m very confident that we can save 99 percent of everything in Mandan if we work together.”
Mandan will continue building an earthen levee to protect areas northwest of the Memorial Bridge and ring dikes around the wastewater treatment facility, though residents and businesses around the Broken Oar and the water park will have to rely on sandbagging around their property, said Mandan City Engineer Dave Bechtel.
Burleigh County, too, has decided against building levees to protect neighborhoods along the river because “what we could do was not feasible or we’re running out of time,” Bitner said.
Morton County does not expect to do any diking because the developments along the river were either above the levels projected for flooding or nearly impossible to protect, Strinden said. The county has put a voluntary evacuation order for Tokash Timber Haven and the Jette Beach area, though some residents farther north might eventually choose to leave their homes.
To monitor river levels, go to http://waterwatch.usgs.gov/new/?m=flood&w=map&r=nd.