The eyes on top of the pine needles enable a crane to lift each one out of its slot in the Spillway locks enabling the water from the swollen Mississippi to flow into the Bonnet Carre' Spillway.
The gauge on the River side of the locks determines the need to open the Spillway.
When the U. S. Army Corps of Engineers determine it necessary, the needles will be pulled and the Mississippi will flow into the Spillway until it empties into Lake Pontchartrain.