What is a levee “boil”?
A levee boil is caused by water seeping under the levee and pushing its way up to the surface on the landside of the levee. Since the water level is much higher in the river during a flood, the water being pushed under the levee is under pressure and when it reaches the surface it bubbles up like a small geyser, hence the term “boil”. If the pressure is high, the water being forced under the levee may begin to push soil materials from within or under the levee. This can be a very dangerous situation because if enough material is eroded from underneath the levee, the levee could collapse allowing water to pour over the top and eventually fail the entire levee. The typical remedy for a boil is to ring it with sand bags high enough to equalize the pressure and stop the flow of water — or least reduce the pressure so no soil is being carried and the water flow is clear.
