Extensive flooding from the Mississippi River

Large amounts of rainfall and snowmelt throughout the Midwest caused the Mississippi River to swell to record conditions, the biggest flood below Memphis since the great flood of 1927, leaving in its wake extensive flooding. Here in southern Louisiana, the crest of this flood is just now reaching us.  Many people in the Atchafalaya River basin have been forced to evacuate.

In the meantime, those living under the protection of the levee system are left to wonder if the current management of the river is really the best way, because while the levees protect from floods, they also deprive delta wetlands of life-giving sediments. Though people may survive the river flood, their protection from hurricanes crumbles as the delta disappears around them

Meeting people in a parking lot at 7:30 a.m. is not usually my favorite way to start off a Saturday, but I had an opportunity last weekend to see the Mississippi River as it may have been 200 years ago. As a scientist that was chance I just couldn’t miss. Along with researchers from the Lake Pontchartrain Basin Foundation (LPBF), I headed down to Bohemia, which sits on the east bank of the lower Mississippi River. It is a section of the river where no levees exist, and the forest and marshes are only separated from the river by a natural low ridge built by the river itself as it deposited sediment during previous floods. Even under the high-water conditions that occur every spring, the ridge usually keeps the river separate from these habitats, but when the river reaches flood conditions it overtops the ridge, delivering much-needed freshwater, nutrients and sediment to the wetlands.

While his researchers waded in the water rushing from the river to survey along the gravel road that runs through Bohemia, Dr. John Lopez of LPBF gave me a tour of the area. John and his group are trying to understand how the water flows through this un-leveed area when the river is high and if this periodic connection to the river is the key to the extensive and lush marshes that can be found here. North of here, the river is straitjacketed by artificial levees, leaving the wetlands of the delta cut off from the freshwater and sediment that is critical for their continued survival. As a result, these coastal areas are disappearing at a rate of a football field every 38 minutes, taking with them essential habitat for birds and fish, as well as the livelihoods of many residents in southern Louisiana.

A former road

Soon I got a chance to wade down the gravel road and participate in the some surveying myself. There were several places where the river was flowing so quickly over the road that I had to be careful to stay on my feet. If there was any doubt left in my mind, this experience showed me that the Mississippi is still mighty and capable of remarkable destruction.

The current method of river management is to build higher and higher levees to funnel water down the river and past communities.  A few key spillways offer safety valves, shunting water away from densely populated communities during big floods like this one.

But this method leaves us one accident, one levee failure away from catastrophe. Instead, we can continue to use a levee system, but also restore the natural defenses along the river’s floodplain. In Louisiana this means reconnecting the river with its delta through controlled openings – diversions – that during high river flow can deliver water, sediment and nutrients to delta wetlands, strengthening the ecosystem. These openings will also provide more safety valves for shunting water and reducing the strain on the levee system that protects communities.

I have to admit, I was terrified to visit the overflowing banks of the Mighty Mississippi this week.  Not knowing what to expect (no one alive can remember the Mississippi delta at this flood stage), my two-hour preparation meeting had me fretting for my very survival.

American Alligator (credit: Theresa T. Baldwin)

But nightmares and warnings of snakes, alligators, and a current that could sweep you off your feet at a 6-inch depth couldn’t keep me away from this trip.  Why?  Because this was my shot at seeing the river work—this was my shot at seeing the process that built the rich ecosystem of southeast Louisiana and the land on which the city of New Orleans lies.  Though it didn’t help that as we soldiered out to the flooded marsh, seasoned oil field workers watched us from a muster station perched 20 feet in the air, yelling, “Watch out for the snakes!”

With all of the artificial levees lining the river banks, I was out to explore a 10-mile stretch south of New Orleans where only a natural ridge separates the river from the marsh.  As you might imagine, it is overtopping at this moment and the muddy river water (critical freshwater and sediment for the marsh) is inundating the adjacent wetlands.  I went with an important purpose: to help a team of scientists collect data to better understand the deltaic process of land-building and marsh nourishment.  This is a critical concept to understand, as we’re losing about a football field of the delta every 38 minutes largely due to mismanagement of the river.

I survived and it was well-worth the bravery.  I did see a snake, but we also saw just what the scientists had hoped to see—a  transformed landscape with water steadily flowing over large swaths of marshland.   The team, scientists from NWF’s local partner organization, Lake Pontchartrain Basin Foundation, have closely studied this unique stretch of river for years.  As we waded knee-deep in the flood, we collected data like flow rates, depth, salinity, and turbidity (how much sediment is in the water).  At the end of the day, we visited an old trapper’s canal that the scientists had previously named “Ezra’s Gully” after a team-member.  The canal is about a quarter-mile long and stretches from the river to the marsh.  As we approached from the marsh end, everyone was shocked to see whitewater rapids pouring out of what is typically a dry or muddy canal.  We disembarked from the boat and surveyed an area that I would have sworn was somewhere in the Appalachian Mountains if I didn’t know better.  Streams of cool water rushed by through the shade-covered banks and we all sat and stared in amazement.  “It’s like a time machine,” said one of the scientists who has studied Louisiana wetlands for decades.

The great thing is, the Mississippi is still mighty and we can restore the process that created and sustained this treasured part of America.  Reconnecting the river to the wetlands can help save Louisiana’s coast and protect communities and wildlife that call it home.