Mississippi Flood update: Morganza Spillway opening imminent

May 13, 2011 | Floods & Floodplains, Small Streams & Wetlands, Clean Water

Shana Udvardy
Director, Flood Management Policy

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The U.S. Army Corps of Engineers is poised to open the fourth and final major floodway on the Mississippi River to ease pressure on levees and save populated areas from record-breaking floods.

To begin relieving the flooding, the Bonnet Carré Spillway was opened on May 9th. But the opening of the Bonnet Carré is proving to be insufficient. With river flows registering at 1.36 million cubic feet per second, the Corps is saying it could open the Morganza Spillway.

If the Morganza remains closed, the rising Mississippi could likely destroy levees and inundate New Orleans with up to 25 feet of water.

Opening the Morganza Spillway does not come without cost. It is estimated that roughly 3 million acres will be impacted, which includes 18,000 acres of farmland, 2,500 people, and 11,000 structures. Additionally, in correspondence to President Barack Obama, Governor Jindal indicated that state-estimated costs post-Morganza opening to be at least $80 million in just the first 30 days.

As we grapple with the severity of the Mississippi River flooding, many are asking how we can better protect communities from floods in the future. Answering this truthfully means taking a hard look at the federal policies that have helped to incentivize an over-reliance on levees, dams, and floodwalls which has actually increased flood risk. We’ve lined the Mississippi River with levees and floodwalls, making flooding worse and pushing the problem to downstream communities. Looking to the future, we need to restore our "natural defenses" -- healthy rivers, wetlands, and floodplains that can help absorb and slow floodwaters.

As our board member Jeffrey F. Mount, geology professor at the University of California-Davis, was recently quoted by ABC in their article posted May 10:

"We have a system of federal regulations that are inadequate for dealing with the risk," said Jeffrey F. Mount, geology professor at the University of California-Davis. "The designation of the 100-year flood plain is in and of itself highly problematic. ... They made this simplistic line in the sand ... and in the end it increased overall risk."

"Additionally, the Federal Emergency Management Agency "underestimated how bad the floods are likely to be in the future," Mount said. "What we thought was based entirely on a historic record of flows and the assumption was made that the past is a predictor of the future. Now, what we're seeing over the last 20 to 30 years is that our storms are getting bigger and they're coming more often."

For additional flood inundation information:

• Times - Picayune Inundation map
• Corps of Engineers Post Morganza Spillway Inundation Map

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