During high-water situations, sand boils can occur a mile or more from the main levee, according to Eckstein. In this case, farther away is better.

“We get concerned when we have sand boils that are pretty close to the toe of the levee,” he said. “If it’s close to the levee, most likely you’re having an impact on the levee. So we want the sand boils to be as far away from the levee as possible. Close is not as good.”

Eckstein said a levee certification program that was begun last year indicates the Corps will have three feet of freeboard between the water line from the Mississippi when it crests and the top of the mainline levee.

Levees for the Yazoo River Backwater System will be overtopped when the Mississippi reaches 56.2 feet on the Vicksburg gauge. “That’s the way the system is designed, and there will be flooding in the Yazoo Backwater area,” he noted. How much depends on additional rainfall and the structural integrity of the backwater levees.

“If we had a levee failure, we could have more than 1.2 million acres of cropland under water and many more residences and businesses flooded,” he said. “We do not believe that will happen, but we are making preparations in the event it should happen.”

In preparation, Corps personnel have been raising the levees where inspections have indicated they are not at full height. (The backwater levee has been found to be one to 11 inches lower than it should be in a few places.) They are also placing plastic coverings over the tops of the levees to try to minimize erosion of the levee surfaces when water begins flowing over the levees.