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Man vs. nature

Can engineering save Louisiana’s coastline?

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Down at the southern tip of Louisiana, on a barrier island called Grand Isle, the stilts holding up the houses are getting taller. There are about 20 feet of air between the ground and the top of the pilings holding up a new two-story house on the island’s main drag, running parallel to the Gulf of Mexico. Its neighbors, a few hundred single-family homes and weekend getaways with house names on wooden signs, are almost all raised up off the ground. C’est La Vie is propped about 8 feet up. The Salty Oyster: 12 feet. Riptide: about 15. A nameless rectangular bunker made entirely of cast concrete is 10 feet up on top of a grid of concrete columns and a cinderblock ground floor. Down the road, another set of 10-foot pilings is all that’s left.

Building at any height on Grand Isle is a bold proposition. Seven miles long, a mile across at its widest point and just a few feet above sea level, it’s a tall wave away from disappearing into the Gulf. With a steady onslaught of hurricanes, sea-level rise, and land subsidence, the island’s very existence is improbable. And yet remarkable efforts have been made to preserve this small strip of land, including the dredging and piping of sediment from the Mississippi River to build back its southern shore and replanting the disappearing marsh to its north.

Saving the island is partly about saving the homes of roughly 1,100 full-time residents and the estimated 20,000 who come to Grand Isle during the summers, but it’s also a strategic defense for coastal Louisiana and the Mississippi River Delta, where subsiding land and rising waters have caused the loss of more than 2,000 square miles of land between 1932 and 2016, according to the U.S. Geological Survey. That’s about a football field’s worth of land roughly every 100 minutes in recent years. In addition to being a scenic vacation destination, Grand Isle is a crucial buffer that’s helping Louisiana hold on to its delta a little longer.

“You see stories in the media on global climate change and cities like San Francisco or Miami, how they’re going to, 50 years from now, be having recurring tidal flooding and things like that,” says Corey Miller, outreach and engagement director of the Coalition to Restore Coastal Louisiana. “Here in Louisiana, we’re experiencing a little bit of an early glimpse at what that’s going to look like.”

Coastal Louisiana is on the front lines of a battle against land loss common to river deltas around the world, from the Nile to the Mekong, where extreme weather and rising sea levels are chewing away at coastal lands. As in many of these regions, Louisiana’s land loss has been unintentionally exacerbated by projects that were meant to be beneficial—river-control structures to make the Mississippi River’s path more dependable, levees built on its shores to prevent the flooding of cities like Baton Rouge and New Orleans, canals cut to ease the movement of goods from what’s become one of the most important ports in the country. In many ways, these projects have enabled coastal Louisiana to thrive. But they’ve also severely limited the river’s ability to deposit its sediment—the natural process that built this delta in the first place.

“The idea now,” says Ehab Meselhe, a coastal wetlands expert and former vice president for engineering at the Water Institute of the Gulf, from his office on a refurbished dock in Baton Rouge that juts out over the Mississippi River, “is how can we find solutions or strategies that can help us reconnect the river to the basin, find an effective way, as natural as possible and as self sustaining as possible, to build land while we are maintaining coastal Louisiana as a working coast?”

This balance of ecology and economy is at the root of a grand transition underway in coastal Louisiana. In the past, the delta ecology was mostly overlooked as government officials prioritized flood controls and the region’s economic growth. Today, under a $50 billion, 50-year Coastal Master Plan created in the wake of Hurricane Katrina and led by the state’s Coastal Protection and Restoration Authority (CPRA), more than 100 projects, like those on Grand Isle, are in progress to try to help the delta’s ecology recover while allowing communities and businesses to carry on.

Both the heavily engineered flood controls of the past and the ecological protection currently being prioritized are complex, systemic, and regional, with wide-ranging implications. But there are two scale models—one hand-built of concrete and steel on a 200-acre field back in the 1940s, and the other laser-etched earlier this year using billions of data points in a state-of-the-art water campus—that offer a way to physically witness the consequences of these diverging interventions.

Seeing both is a helpful way of understanding the scope of the problems the region faces, as well as the potential for reversing some of the mistakes of the past. In projects now being modeled and built here for the first time ever, the Mississippi River Delta is a testing ground for new ways of thinking about how to balance a vibrant and active population center with the needs of the natural ecology on which it thrives. As the land subsides and the tides rise, it’s an existential matter in coastal Louisiana.

The results of these tests also may have implications for coastal regions worldwide. “This is the most comprehensive laboratory in the world,” Meselhe says. “If we can figure it out here, I really mean it, I think we can export that knowledge to other places.”

In a regional park on the edge of the small central Mississippi town of Clinton, across from a field full of Saturday morning kids’ soccer games and through a hole in a fence, lies one of the most consequential scale models ever built. Spread over 210 acres and laid in thousands of roughly 100-square-foot panels of cast concrete is a monumental miniaturization of nearly the entire drainage basin of the Mississippi River.

Running from its headwaters in Minnesota more than 2,300 miles to its Southern Louisiana mouth into the Gulf of Mexico, the Mississippi River is the world’s fourth-longest river. Its basin—the land that drains through streams and flows in groundwaters into the Mississippi along its path—is even grander, a triangular chunk of the country stretching from Montana to New York to Louisiana, covering 1.25 million square miles and accounting for an estimated 41 percent of the continental United States. The concrete panels laid out here model that massive basin, and the model was employed for several decades by the U.S. Army Corps of Engineers to figure out how to control the mighty river. It was used to test and then implement flood-control protections that quantifiably saved lives.

Parked inconspicuously among the soccer families this Saturday, Bradley Garrett digs through a bag in the back of a minivan looking for a stolen hotel bathrobe. “It’s the warmest thing I’ve got in here. I didn’t pack for this,” says Garrett, a research fellow at the University of Sydney known for his work in “experimental” geography, including trespass-based urban exploring. He puts on the robe and slips a loose bottle of Negra Modelo into its front pocket. The weather, unexpectedly, is in the 50s—the cold tail of a massive spring storm that swung through the region the day before. There were tornado warnings here and flooding in the streets back in New Orleans, where Garrett and about 10,000 other geographers had gathered for their profession’s mega-event, the annual meeting of the American Association of Geographers. The storm caused an unfortunate one-day delay of this unofficial field trip to the model, paring back what should have been a vanful of eager geographers to just Garrett and Harriet Hawkins, a professor of GeoHumanities at Royal Holloway, University of London, and myself.

Stepping through the fence and trudging across the soaked ground into the trees, we looked for the hidden edge of the river basin. Not more than 200 yards from the soccer fields, the short forest opens up, and the scrubby ground is replaced by massive slabs of concrete. We’re suddenly walking on a human-sized relief map. The serpentine slitherings of the river are canyons in the concrete, deep here, wide there, oxbowing and bifurcating and braiding.

Leaves and muck sit inside the river’s path, which we follow north from the pit and pump system we determine to be the end point of the model river. We bend down and look at the tiny details, the wavy topography, the levees along its edges, the brass plugs that simulated drag on the river bottom, the swerves of the Mississippi’s naturally changing course frozen in concrete. It goes on and on, seemingly forever, spiderwebbing out into the trees, loose panels rocking beneath our feet.

The only other people we see are three teenage boys, high school seniors from Clinton, and they’re clearly less impressed than our trio of outsiders. “We’re here all the time,” one of them says. “There’s not much else to do around here.” But they do admit to a certain level of fandom; they made a point of coming out after a somewhat rare snowfall this past winter to climb up onto the four-story observation tower the Army Corps built to look down on their shrunken territory. The wind up there was so cold they could only stand it for a minute. Anyway, with the snow already covering the model, there wasn’t much to see.

In the full spring light, the Mississippi River Basin Model is catnip for geography professors. Temporalities, ontologies, and epistemologies are discussed. Reading aloud from a thorough Places Journal article about the model by Kristi Dykema Cheramie, Hawkins explains that construction of the model started in 1943, 15 years after devastating flooding on the Mississippi spurred the passage of the Flood Control Act of 1928. The land was cleared and prepared through the labor of nearly 2,000 German prisoners of war, some handpicked for their engineering and construction experience. The model was so vast that design of the panels had to account for the curvature of the earth. Garrett turns around, jaw dropped.

William Widmer/Redux

Wrapping our heads around the model and its relationship with the river it represents is a collective effort. The model, after all, was not some garage hobbyist’s replica, but rather an experimental tool used to test out massive infrastructural interventions on the country’s most important river system. Dams or flow controls tested on the model were often later built out at full scale on the actual river. Rainfall predictions pumped through the model helped Army Corps officials know in 1952, for example, to evacuate thousands of people ahead of an impending flood in Omaha, preventing an estimated $65 million in damages and certain loss of life.

Tests in the model would lead to infrastructural changes in the full-scale landscape, which would then require permanent changes to the model to accurately represent the now-altered river system. Hawkins compares it to the Jorge Luis Borges story of an empire so reverent of the art of cartography that it committed to mapping its own realm at a ratio of one-to-one, a process that would result in its constant expansion and the constant need to map it all over again. The model, Garrett says, is a sort of built version of this paradox, both a place and a representation of a place, separate but inextricably linked.

By the time the model was pulled out of regular service in the 1970s and replaced by increasingly advanced computer modeling, its experiments provided justification for the construction of dozens of dams, reservoirs, and other water controls along the Mississippi and its tributaries. These controls helped prevent floods and maintain the functionality of the Mississippi as an economic engine that powers dozens of cities along its course, from St. Louis to Memphis to Baton Rouge to, most of all, New Orleans.

But the city most closely tied to the river wasn’t even part of the picture. The model ends its reproduction of the river’s basin around Baton Rouge, 150 miles north of where the river meets the gulf. South of Baton Rouge, the Army Corps determined, there was no more significant inflow that would affect the river’s potential to flood. So New Orleans and the vast river delta were left out of the model, deemed irrelevant to the question at hand. It was a practical decision, but one that encased in concrete a mode of thinking about the river that irreversibly altered the region’s future.

From a second-story catwalk in a warehouse near downtown Baton Rouge, you can look down on the entirety of Southeast Louisiana. From Louisiana’s boot instep in the west to the border of Mississippi in the east, and from the Mississippi River’s curve past the town of Donaldsonville northwest of New Orleans to its birdfoot-shaped dissipation into the Gulf of Mexico, roughly 14,000 square miles is shrunk to the scale of a building. Measuring 90 by 120 feet, this model is about the size of two basketball courts, the contours of the landscape laser-etched into 216 panels of white high-density foam. Unlabeled, the model’s dominant feature is the river, half a foot wide, meandering southward 190 miles, carving its crescent around New Orleans before splintering a thousand capillaries out into the ocean. But when a grid of mounted projectors turns on and blankets the white landscape with the detail of full-color satellite imagery, the model is less about the river than about the distinction between land and water.

This model is the high-resolution, zoomed-in version of that low-res concrete model back in Mississippi, and it can show, with remarkable precision, not just the river’s potential to flood, but also its water levels relative to downriver levees, its interaction with projected sea-level rise, and even the movement of the heavy sand at its bottom that gets carried down and deposited to build the delta itself. With computer-controlled water pumps, precise flow and sediment data, and specially engineered black-plastic particles that replicate the movement of river sand, the model can mimic a year’s worth of river activity in about an hour.

Clint Willson, a professor of civil and environmental engineering at Louisiana State University and director of the university’s Center for River Studies, shows me around the model, the highlight of a new multi-building “water campus” occupied by researchers from LSU, the CPRA, the Water Institute of the Gulf, and a handful of river- and coastal-related NGOs. “Here, you actually see what’s happening,” he says, looking out over the model. “So if you want to say, ‘Well, this seems a little strange, why is this thing happening,’ you can actually go stand over it and watch what happens and go, ‘Oh, wow, I see the progression of that change or that process.’”

You can also see what happens when you try something radical. On the day I visit the model, the black particles have collected, after the water pumps have produced a year’s worth of flow, in a part of the delta about 20 miles south of New Orleans that has turned from delta marsh to open water over the past few decades. The model is showing what could happen when one of the Coastal Master Plan’s key projects is implemented. Known as a sediment diversion, the project would replace the hard wall of a river levee with a gate structure that, given the right conditions, would be opened to divert some river water and its land-building sediment out into the disappearing delta. Estimated to cost $1.3 billion, it’s an experimental project that hasn’t been tried anywhere else in the world. If those black particles on the model are right, a strategically opened sediment diversion could build upward of a square mile of land per year, according to one estimate.

William Widmer/Redux

This is one of two sediment-diversion projects steadily moving their way through the design and engineering process, and all the permits could be in place by 2020. Like the dams, levees, and reservoirs tested and built using the old model, this is another form of human control over the river. But instead of single-mindedly constraining the river at the expense of its ecology, sediment diversions strategically allow the river to act naturally.

“Deltas are almost living entities. They are born, they get to a peak, they get old, they die out, and then a new path is formed, and those older deltas are where the barrier islands are coming from. So it’s a natural process. We kind of stopped that natural process from its cycle,” says Meselhe, whose calculations and computer modeling have provided the scientific validation that the diversion process can build land. “The sediment diversion is not a new concept. It’s actually trying to reestablish a natural concept,” he says. “It’s a natural process, but it’s on purpose now.”

The Barataria Basin, a liminal zone of marsh and water in Plaquemines Parish, south of New Orleans, is one of the country’s prime fishing and shrimping areas. It’s also one of the hotspots of coastal land loss in Louisiana—and really the world. The CPRA estimates that this basin and another directly on the other side of the river have lost 700 square miles of land since the 1930s. A grassy field down the road from an oil refinery could soon hold the key to slowing that land loss.

It’s here where the CPRA plans to cut the Mid-Barataria Sediment Diversion, a gated two-mile concrete channel spurring off the side of the Mississippi River and dumping out into the Barataria Basin. The diversion is designed to open only when the river is flowing fast enough for the heavy land-building sediment at the river’s bottom to be carried downstream—450,000 cubic feet per second, a flow it tends to hit regularly between January and August. When opened, the diversion will move as much as 75,000 cubic feet per second of river water out into the basin. After 20 years of operation, it’s estimated the diversion could create up to 22 square miles of land. The project is currently undergoing an environmental-impact assessment, and that report is expected to be made public in late 2019.

Aside from empty fields, there’s not much immediately around the planned diversion site. About a mile down the road is a four-block African-American community called Ironton, and another mile down is the Myrtle Grove Marina, where a few dozen houses perch on spits of land and look out on backyard docks. Across the street, the Myrtle Grove Bar is completely empty on a warm spring evening. The bartender is watching a singing competition on television and says the bar is less a drinking establishment than a pitstop for recreational fishermen heading back to the city after weekends on the water. She lives up the road in Ironton, and had never heard of the sediment diversion.

Plenty of others have been following the project for years, and they worry that infusing so much freshwater into the fertile spawning grounds of shrimp and oysters in the Barataria Basin could temporarily wipe out an ecosystem—and an industry.

Sandy Nguyen runs Coastal Communities Consulting, a nonprofit that advocates on behalf of thousands of fishermen in Southeast Louisiana. The wife of a shrimper, she has worked for more than 25 years to bridge the divide between the governmental entities making plans for the coast and the largely uneducated and immigrant fishing communities that are on these waters every day. She says those communities are all in favor of coastal restoration—more coast means better fishing, after all—but she worries that not enough has been done to ensure the diversion won’t jeopardize their livelihoods.

“If it does build land 10, 15 years down the road, we’ll have more spawning grounds for our seafood,” she says. “However, commercial fishing is a daily thing. They have to work every day to make ends meet. Who’s going to feed them through the 10 or 20 years that takes?”

Liz Williams Russell, coastal community resilience director at Foundation for Louisiana, has been helping lead a community-based planning process in this area, trying to better involve locals in deciding future projects that address coastal change. But it can be a losing battle. Even if the planned sediment diversion doesn’t kill off the local fishing industry, the land there is still subsiding and the sea level is still rising, making it harder for these communities to survive. “People have already seen the land disappearing around them,” she says. “People have already seen jobs change accordingly. They’ve seen resources and amenities in their locations change. They’ve seen people move. The population of people who can afford to move have been picking up and leaving.”

As the land disappears, the coastal community here will inevitably shrink. But the CPRA is hoping that the implementation of the master plan will slow that decline and enable many communities to stay put.

“We understand the work that happens there, we understand there are residents there, and it would be a very costly and logistical nightmare to move all those people,” says Rudy Simoneaux, engineer manager at CPRA. “So what we’re trying to do is strike a balance where we can still build land and maintain that working coast.”

Diverting sediment is the CPRA’s key to striking that balance. Though projects of the past have relied solely on dredging millions of cubic yards of sediment from ephemeral sandbars in the river to rebuild places like the barrier island Grand Isle, dredging has its limits. “We did an analysis on it, and even if we were to have the money to dredge all of these sites, you still couldn’t build as much land as a diversion,” Simoneaux says. “You physically don’t have the sediment to dredge.”

For all the uncertainty about the impacts of the planned sediment diversion, one thing is certain: Redirecting part of the river’s flow can build land. In the 1950s, the U.S. Army Corps of Engineers determined that, if left unchecked, the Mississippi River was likely to change its course dramatically, as rivers do, shifting the majority of its flow far to the west via the Atchafalaya River, a shorter and steeper path to the Gulf. To prevent this change and its impacts on the industry and economy of the region, they built an early form of a sediment diversion, a large concrete gate structure 150 miles north of New Orleans that limited how much water from the Mississippi took that shorter path. Now, a half century later, the end point of the Atchafalaya’s course to the Gulf is one of only a handful of places on the map of coastal Louisiana where land is actually being built rather than lost. The redirected river ended up doing what it naturally does: It has been building delta.

The actual amount of delta that’s grown there over the course of decades is only about 6 square miles. That’s a drop in the bucket compared to the football field’s worth of land that disappears in this region every two hours.

But the scale of the challenge only underscores the need to do something now. In Meselhe’s office back in Baton Rouge, the river flowing beneath the building had risen after the recent storm, its water lapping directly below his window, the pulse of a massive living system. It’s complex, and difficult to visualize without the help of a big model, but high flows like this one are part of what feeds the delta, and the structures we’ve built to control these flows have a long tail of effects on that ecology. Meselhe says the science shows that, with the right interventions implemented sooner rather than later, that ecology can be restored. “We’re losing the system while we are continuing to discuss. So we can’t continue to discuss forever,” he says. “We cannot. Because no action is an action by itself. It is an action of giving up. I feel that people have started to realize that there is a limited window of opportunity and that window is closing.”

Nate Berg is a freelance journalist writing primarily about cities, design, and technology. He lives in Berlin.

Editor: Sara Polsky


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