COLUMBIA — Peak releases from Gavins Point Dam should arrive at Boonville in the middle of next week, but forecasters do not expect that water to cause major flooding as soon as it arrives.
The Army Corps of Engineers and National Weather Service are holding to forecasts for record releases upstream to eventually raise the Missouri River to between 27 and 33 feet at Boonville, hydrologist Kevin Low at the Missouri Basin River Forecast Center said.
Gale Blomenkamp of the Boone County Fire Protection District said work will begin to place sandbags and retaining walls in towns along the river when river forecasts predict a level of 27 feet at Boonville, the closest gauge upriver from Boone County.
Above 30 feet, the river threatens to overflow levees in Boone County. The record crest on the Missouri River at Boonville was 37.1 feet in 1993.
The water from Gavins Point is not enough to lift the river to 27 feet at Boonville by itself, but it could cause a rise to 24 or 25 feet, Low said. Average rainfall in the Missouri River basin below Gavins Point would push the river into the forecast range.
"If we had no rain, even on the day the releases arrived we wouldn't get to 27," Low said. "But I assure you, some day this summer we will get to 27 feet. If we get a significant event, it's going to be above 33."
By a significant event, Low means several consecutive days of above-average rainfall. An event like that is not out of the question. Summer rainfall has surpassed the norm in the lower Missouri River basin each of the past three years.
Water from Gavins Point has taken longer than expected to reach Boonville. The dam has been releasing more than 100,000 cubic feet of water per second since the beginning of June and was at 150,000 cubic feet per second on Thursday, more than double the previous record release in 1997.
Army Corps of Engineers spokesman Carlos Lazo said that along with river floodwaters backing up in tributaries, inundated floodplains along the river have delayed rises downstream so far.
"Because we've been releasing gradually and didn't go to 150,000 cfs right away, you're not going to see that immediate jump," he said. "It's not going to be a humongous rise in the river drastically. It will rise, but it could be inches at first."
Blomenkamp said the city of Columbia, Boone County government and representatives from towns along the river have held ongoing meetings and continue to monitor levels and forecasts.
"All indications are that it will eventually get here. We just keep looking out, and now we see that upward trend starting," Blomenkamp said.