Omaha Public Radio News
Thu June 23, 2011
Boils a major hazard with river flooding
By Cheril Lee
Omaha, NE – A UNO Geology Professor says sand boils are one of the biggest problems that can occur as a result of flooding.
Dr. Harmon Maher says the term boil refers to the flow of water through the ground, including sand and gravel. He says there tends to be lots of sand and gravel in river floodplain areas. Dr. Maher says the trouble begins when the water on one side of a levee is high and the ground on the other side is low, "Basically then, the water can exert pressure on the water beneath the sand and gravel and then it can cause it to flow. If it starts to flow fast enough right at the surface, it can actually lift and start to move the grains. The situation changes. Instead of the little sand particles resting against each other,the water can start to move it."
Dr. Maher says when boils happen and sediment starts to move, a feedback process can happen where flow becomes even greater. He says this can cause a levee to give way quickly. Dr. Maher says one of the quickest ways to combat the problem is to load the boil with sandbags to keep the sand in place. For up to date information on the flooding situation, the website is www.nema.ne.gov.