The pumping stations have long been called "siphons." As long as they are operating they move water from the low side, "the city" to the high side, "the lake." They have to pump uphill to accomplish their mission. What would happen if they suddenly lost power?

Without intervention they would run backwards and add to the flooding problem on the city side. Water running from the lake to the city is called "backflow." Jefferson Parish flooding during Katrina is suspected to have been aggravated by backflow.

The pumping stations all have some sort of backflow prevention. Most use high pressure air in the siphons to break the suction. Effectiveness of this approach is under debate. Gates are another alternative.

In June 2007 the Corps announced that interim backflow protection would not be in place for the 2007 Hurricane Season.