Afternoon Diversions

A symposium on sediment included a visit to some of the South Louisiana sites that seek to control the surrounding waters. Christopher Staudinger offers a dispatch from the diversion excursion.


Cars pass periodically on Highway 18 below the Davis Pond Diversion structure. It’s plain and concrete, not unlike the other outfall, intake, or giant pipes that sometimes stick out of the Mississippi River levee. The drive past the Diversion is fairly bucolic, flanked on either side by a stalled railroad train and the river batture. The scene doesn’t evoke the rancor and the anguish that's often visible in meetings or headlines about Louisiana’s rapidly disappearing coast, but the water moved in dramatic fashion for the participants of Dredgefest who visited the structure on Friday (Jan. 17).  9000 cubic feet of water shot beneath their feet every second.  Davis Pond was the second stop on a tour that visited an array of dredge-related sites, from the mouth of Bayou St. John to the Bonnet Carré spillway gates in St. Charles Parish. 


The diversion excursion was the finale of last week’s Dredgefest, a traveling, annual summit that investigates “human sediment handling processes.”  The event is organized by a six-person collective of writers, theorists, and landscape architects who get excited about dirt and how it moves.  


“What we do is bring a speculative, sort of weird architecture, and in some cases an almost science fictional perspective to things,” says Tim Maly, one of the organizers. He writes about design and 3D printing and is a Fellow at Harvard’s Metalab.  The collaborators’ scope, like the sites that the tour visited, can be vast and lofty.  


“The natural shifting of the landscape and our tendency to try to pin it down puts us in conflict with a lot of very powerful forces," Maly said, and those forces are sometimes more evident than others. The festival subjects can be as innocuous as the orange silt fences bulging near construction sites, or as dramatic as the water in the Davis diversion, where the water thrashed and snapped a mat of driftwood tree trunks as it moved through the sluice gates and onto the Barataria Basin.


Adam Mandelman, a PhD candidate in Geography at the University of Wisconsin, attended Dredgefest for his dissertation research, part of which focuses on the social interactions between people and water in Southern Louisiana. He pointed to a spot near the diversion where an 1884 crevasse broke a hole in the levee that was four football fields long. The gap allowed an incomprehensible amount of water compared to what flows through the Davis, which he calls “a puny diversion…compared to some of what's proposed in the most recent Coastal Master Plan (it includes a couple that can divert as much as 250,000 cfs at the highest stages of the river).”  


Chuck Villarrubia, a senior scientist with the state’s Coastal Protection and Restoration Authority, greeted the tour at the structure, which, he said, has helped improve the health of the Barataria Bay estuary primarily by combating saltwater intrusion. The structure is meant to mimic the Mississippi River’s flooding tendencies, which, before the construction of the levees, delivered an annual dose of sediment-rich fresh water to the land beyond its banks.


But the diversion has not gone without contention. Some, like George Ricks of the Save Louisiana Coalition, have said that the diversions weaken existing marshes. He advocates for direct land building through dredging, and in an opinion piece about the Caernarvon diversion published by the Lens, he wrote, “Diverted water had transformed the stronger, brackish water vegetation into freshwater vegetation with shallow root systems. Instead of providing the much-touted buffer against (Hurricane Katrina’s) storm surge, the whole marsh was peeled up like a carpet!”


Oystermen have complained that the diversion has altered the salinity enough to stunt oyster beds. Still others, like the Restore or Retreat campaign, have said that the structure hasn’t released enough freshwater.  Villarrubia addressed them without prompting. 


“It’s going to take a lot of different approaches to solve this problem,” the state scientist said.


The tour, especially a visit to Holy Rosary Cemetery in St. Charles Parish, showed how far the concept of “dredge” can be taken. The cemetery is surrounded on most of its sides by the smokestacks of a Union Carbide complex. It is often the poster child for the tensions of the petrochemical corridor on the Mississippi River. Asked how the stop connected to Dredgefest’s work, Maly pointed out the ship moored in the channel. The  stacks rose above the levee, which was also overhung by the pipes from the complex.


“The Mississippi is dredged to the depth that it is so the vessel can be there, because of petrochem,” Maly said. “That refinery, that terrain, in its history, it was wetlands on the Mississippi. And then it became farm and plantations, and then it became a chemical facility. And the need to keep first the farm…and then the chemical facility dry is what lead to the levees, which then leads to the loss of wetlands and the slow sinking of Louisiana.”


Much of South Louisiana is tied up in this history of simultaneous reliance and strangulation from the Mississippi’s waters. It makes New Orleans an apt place for the second installment of festival devoted to the movement of silt.  But the message was slightly different from that of the first summit in New York, where, Maly says, it’s easy to forget you’re living on a coastal landscape.  


“In New York, it was reasonable for us to come in and say, ‘hey, there’s this crazy thing happening that you’re completely unaware of and you should pay attention to it," the organizer said.


Rather, the Louisiana installment of the festival was more about learning from people who deal with dredge in what he calls “an ongoing crisis.”


Nevertheless, the tour and the summit shed light on plenty of material that's often overlooked by the day to day Louisianian. Maly brought up the Old River Control structure, north of Baton Rouge, which participants visited earlier in the week. Were it not for the mind-bogglingly massive structure, the Mississippi’s waters would largely bypass New Orleans and flow down the Atchafalaya.  




“Old River Control’s job is to stop history and to freeze the flow between those two rivers at a particular date.  And that’s…that’s hard,” he said.

At the Davis Pond Diversion, It’s difficult to know whether the people in the cars on Highway 18 realize how much water, wood, and sediment passes beneath the asphalt below them. Blake Chaisson, the gate’s operator since its completion in 2002, sees it almost every day. Above the torrent, he leaned on the railing and said, “That water’s more powerful than you could even imagine.”


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