River expected to crest here today
Published 12:00 am Friday, January 28, 2005
These two houses on Mississippi 465 are among those that have taken on water because they were not under the watershed of the Brunswick Extension Levee. (MEREDITH SPENCER The Vicksburg Post)
[1/28/05] Peter Nimrod and Kevin Pace will rest a little easier Saturday because the Mississippi River is expected to crest at Vicksburg today at 44.8 feet.
Nimrod, chief engineer for the Mississippi Levee Board, and Pace, a civil engineer for the U.S. Army Corps of Engineers, have been monitoring the 212 miles of levees in Washington, Humphreys, Bolivar, Issaquena, Sharkey and Warren counties. Pace’s group has also been monitoring levees in Louisiana.
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Twice-daily patrols have visited trouble spots where water is gutting the interior of a levee.
“We’re looking for flow, bumps or budges … any inconsistencies,” Pace said.
Usually, only levee board employees monitor the levees. That changes when the river gets to Phase I flood stage, which is 1 foot above flood stage, 43 feet on the Vicksburg gauge. It topped flood stage last Saturday.
“When we get in this high-water stage, we need help,” Nimrod said.
The river crested in Greenville on Wednesday at 50.5 feet, about 2 feet above flood stage there. The 7 a.m. reading at the Vicksburg bridges today was 44.3 feet, identical to the reading at the same time Thursday and indicating the river may have topped out earlier than expected.
The Corps of Engineers has been helping to tame the river since the Flood Control Act of 1928, prompted by the 1927 flood. A levee system was in place before that flood, but failed in many places. Today’s system has been a project in progress since.
The river drains 41 percent of the water in the United States, Nimrod said.
A relatively light amount of rainfall has made the inspectors’ jobs easier, as well. During heavy rains, it’s hard to distinguish between seepage and ordinary runoff, he said.
“We’ve lucked out this time,” Pace said.
One of the most-watched areas is at Buck Chute near Eagle Lake in northwest Warren County. Until 1999, several dozen sand boils had sprung up in the few hundred yards between the Brunswick Extension Levee and the lake.
Sand boils are created when the water pressure on the levee is so great that it seeps underground. Small springs pop up, carrying dirt with it. If not fixed, the lost dirt could cause a cavity in the levee and cause it to fail, Nimrod said.
“When you have a levee failure, it’s usually not due to overtopping. It’s because of undermining,” Nimrod said.
Most of the time, sand boils are treated by putting sandbags around the water, putting a “head” on top of the boil. The velocity of the water slows because the pressure on top of the water is lessened, Pace said.
In the case of Buck Chute, so many boils had sprung up that engineers installed six relief wells in 1999. The 90-foot-deep wells have filters to prevent dirt from being taken with the water.
“You’re not going to be able to stop seeping water, but you can stop the material,” Nimrod said.
“They’ve done their job. They’ve really slowed down the water,” Nimrod said.