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Matt Rota
...and if the Creek Don't Rise
Blog -
Tuesday, 10 May 2011 12:53

On several occasions I’ve witnessed the awesome power of the Mississippi River; the most striking was the flood of 1993.  At the time, I helped fill sand bags in an ultimately futile effort to save Valmeyer, IL, a small farming community down the bluff where I went to school.

Now I am in New Orleans and last night I took a bike ride by the Missisippi along the River Walk to take a look at the current record flooding of the Mississippi.  These record flows have already resulted in the Corps’ decision to detonate a “fuse plug” levee in Southern Missouri.  Like a fuse in the electrical wiring of our homes, these “fuses” are levees designed to be broken to preserve the larger integrity of the levee system.  And so the Corps of Engineers  has allowed the Mississippi to temporarily reclaim a portion of its flood plain to keep the water from our cities.

Despite this relief of pressure on the Mississippi River levee system, folks in Louisiana are on pins and needles, and rightfully so.  By the end of the day, we will have opened ­­­­20% of the Bonnet Carré spillway, 30 miles upriver of New Orleans.  If and when it’s fully opened, this will divert approximately 250,000 cubic feet per second (cfs)--about 2.5 Olympic swimming pools every second or 173 Superdomes every day!

The Mississippi is expected to crest at New Orleans on May 23 at 19.5 feet.  To put this into perspective, the river crested at 16.81 feet the last time we had to open the Bonnet Carré in 2008.  (For more on the potential ecological impacts of opening the Bonnet Carré, see Scott Eustis’s blog from last week)

Mississippi_Floodways

While we wait with baited breath to see whether the Corps will open the other controlled spillway in Louisiana (the Morganza spillway, which could divert up to 600,000 cfs into the Atchafalaya River floodway), it is hard not to wonder if there could be an alternative to our current predicament.  While record flows flow down the Mississippi, 500 yards from my back door, valuable sediment is flowing by as well.  The majority of this sediment will simply be pushed off the continental shelf into the Gulf of Mexico.

What else could this sediment be doing? What it did before we constrained the River—building land. This is what the Mississippi did for thousands of years, and continues to do in a haphazard way.  For example, in 2008, and times before high waters overtopped and breached and flowed into the old Bohemia Spillway, which is on the east bank of the Mississippi, south of New Orleans. During this flood, Dr. John Lopez from the Lake Pontchartrain Basin Foundation and others documented the breaching of the levee.  Their preliminary findings (pdf ) showed that this area, due to periodic flooding and sediment deposition, was experiencing less land loss than surrounding areas.  This demonstrates the ability of the Mississippi River to build land during flood events.

First and foremost, we need to make sure that people are safe and not caught in flood waters.  After we avoid as much damage as possible, now is the time to start managing the river better, and start living with the river, as opposed to fighting it.  In Louisiana, this means building land-building diversions that would both utilize sediment to build land and wetlands, and alleviate pressure on river levees.  Further upstream, this means reintroducing the river back to its floodplain.

Which brings me back to Valmeyer.  Despite valiant efforts of the town and surrounding communities, Valmeyer was flooded. The town lives on—just not in the same place.  The entire town moved up on top of the bluffs, and the people no longer have to worry about the Mississippi lapping at their back doors.  Here in South Louisiana, we don’t necessarily have the luxury of getting away from the river—after all many towns in Louisiana, like New Orleans, were built because they were on the Mississippi.  But there are things we could be doing to lessen our risk.  Levees will always be necessary in some areas, but giving the river room, and fully utilizing the sediment in the river to build land would help us have a more amicable relationship with the Mississippi.

Matt is GRN’s Science and Water Policy Director

 

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