Bonnet Carre' Spillway Facts vs Myth

1. When does the Corps of Engineers open the Bonnet Carre' Spillway?

   1. The Corps opens the spillway whenever they want.
   2. The Corps opens the spillway when the stage at New Orleans reaches 20 feet NGVD.
   3. The Corps operates the Bonnet Carre' Spillway when conditions, either stage or flow, present unacceptable stress on the flood control system.

2. Why does the Corps of Engineers open the Bonnet Carre' Spillway when the water in the river is not at the top of the levees?

   1. To prevent unacceptable risk to the Mississippi River flood control system.
   2. The Corps wants to save New Orleans from flooding.
   3. They don't want to wait for levee overflows.

3. When does the Corps of Engineers open the Morganza Floodway?

   1. The Corps never wants to open the Morganza Floodway.
   2. The Morganza Floodway is operated to prevent unacceptable risk to the Mississippi River flood control system.
   3. The Morganza Floodway is opened to affect fewer people than opening the Bonnet Carre' Spillway.

4. Why does Mississippi River water look so muddy?

   1. The Mississippi River is polluted.
   2. The water is just a different color.
   3. The muddy appearance of the river is caused by the transport of highly erodable bottom sediments.

5. When the Corps opens the spillway, does it affect the water quality of Lake Pontchartrain?

   1. Yes, the Mississippi River water harms the water quality of the lake.
   2. The lake experiences elevated levels of nutrients and low salinity in the short-term following a spillway opening, but no negative long-term effects from the spillway opening are evident.
   3. The lake is already polluted, so there is no meaningful effect.

6. What caused the 1997 Lake Ponchartrain algae bloom?

   1. The March 17, 1997, spillway opening.
   2. Increased water temperature, solar radiation, light penetration, and stormwater runoff from the north and south shores.
   3. Both 1 and 2.

The POC for this page: Kathy Gibbs, CEMVN-PA Chief, Public Affairs Office New Orleans,LA 504-862-2201 Fax: 504-862-1724 askthecorps@usace.army.mil