ARABI, Louisiana—The water is breaking gently around the hull of the crew boat Miss Emerson, as if she were puttering across a muddy lake. Instead she is tied at the dock of Port Ship Service, straining at her bowline as a supercharged Mississippi River rushes beneath. On the bank of a levee just over the parish line from New Orleans’ Lower Ninth Ward, Capt. Charles Crawford is preparing to take control of the Valle Azzurra, a big ship coming down the river in a hurry. The Miss Emerson is a transport boat. She will pull alongside the Malta-flagged tanker, and Crawford will board the larger vessel as the ships run momentarily together. He will climb a ladder that hangs over the ship’s port side, whose paint is scraped from a recent trip through the Panama Canal. His assignment: steer the Valle Azzurra safely to Pilottown, where the river meets the sea.

“Where’s mine?” Crawford asks Timmy Lopez, the drawling, tattooed dispatcher, his eyes as blue as the river is brown.

“Coming up on Perry Street,” responds Lopez with a glance at a monitor, as if we were waiting for an Uber instead of a 200-foot ship carrying 10,000 gallons of God knows what around the bend at Algiers Point.

Crawford is a member of the Crescent River Port Pilots Association, a group of elite mariners who steer tankers, freighters, and cruise ships down the 106 treacherous miles between New Orleans and the Bird’s Foot, the Mississippi River’s branching delta. It is specialized terrain, the pilots say, and even an experienced captain would struggle with its eccentricities. Crawford has the demeanor of a Hollywood airplane pilot—tanned, pleasantly lined face, a full head of gray hair. He has been doing this job for 40 years, and this one will be his last. “I always said, ‘I think I’ve got another high river season,’ but this year I said, ‘No, no more,’ ” he says, passing me the association calendar, which he helps photograph and design. “I’ve been doing this a long time, and I’ve seen a lot of high rivers, but I’ve never seen a river this high, this long.”

No one has. The Friday that Crawford sat waiting to board the Valle Azzurra was Day 225 of high water in New Orleans, tying the longest stretch in recorded history, set in 1973. The next day—Saturday, June 8—the record broke, and there is no end in sight.

In New Orleans, the Mississippi River is considered to be at “high water” when it runs through the city at more than 8 feet above sea level. Usually, high water comes in the winter or spring and ends by June. This season, the river rose in November and hasn’t come down. “The length of time it’s gone on is really, really taxing my guys,” said Michael Bopp, the president of the Port Pilots Association. As a pilot, he said, “if you’re not scared, you’re oblivious. Oil, toxic chemicals, acid—you go right by people’s houses with the most toxic stuff known to man. You have a huge responsibility, and especially right now. The velocity and the length of time it’s been high is extraordinarily unusual. We are dying for it to go down.”

Channelization and climate change have helped create a Mississippi River running high and fast, longer than ever before.

Thirty-two states and two Canadian provinces drain through New Orleans. Sediment from the Midwest, distributed through the alluvial plain by regular floods over millions of years, created Louisiana. Since the 1930s, that process has all but stopped: The river is so heavily channelized here that it is invisible from the streets of the city, ferrying its rich silt deeper and deeper into the gulf. It runs higher than the surrounding land, penned in by levees, in John McPhee’s memorable phrase, like a vein on a hand. For the past six months, it has looked like the vein on a hand that’s been lifting weights. America’s wettest 12-month period in recorded history, all those devastating floods in Nebraska, Iowa, Oklahoma, Arkansas … it is all coming down through New Orleans now, putting the world’s most ambitious infrastructure of river control to the test.

It has been a high water season that has, for now, proved the strength and flexibility of the system of shipping, spillways, and levees built to keep New Orleans prosperous and safe. One season is a little scary. But there are signs that the Lower Mississippi may be entering a new era, one where high water comes faster and longer than it ever did before. The river—long an afterthought in this flood-scarred city—might threaten New Orleans once again.

High water moves fast. In the office of the Coast Guard in Algiers Point, across the river from the Bywater neighborhood in New Orleans, there’s a chart on Tony Marinelli’s desk that shows how the river’s speed rises with its height. At the Carrollton Gage, a measuring stick located just off the bank near the Audubon Zoo, 16 feet of water can be counted on to produce an average speed of 5.2 miles per hour at the surface—7.6 feet per second. The Hudson River at Albany, New York, rarely reaches a quarter of that speed. A log floating downriver through New Orleans (and there are quite a few of them at the moment) is traveling at an easy jog, past banks of submerged willow trees bobbing in the current.

Crawford, the pilot, told me that taking a big ship down the Mississippi at high water around Algiers Point is like driving a truck down a road of ice. Taking it up the river might take twice as long as it did this time last year, when the river was 8 feet lower. Right now, everyday river operations are tense. One deckhand likened the situation to a five-alarm fire. There are no barges resting on the riverbanks, because there’s not much levee left above the waterline. Anchors won’t hold in the river bottom. On Wednesday morning, a barge hit the shore in Algiers, knocking over a utility pole and causing a power outage for 5,000 people. Then again, at least things are still moving here: Further north, the Arkansas and Illinois rivers have been closed to commercial traffic entirely due to high water, choking off shipments of corn and soybeans.

Marinelli is the watch supervisor here. From 6 a.m. to 6 p.m., he and his team sit in a dark room, in front of screens that show every ship on the river from Baton Rouge to the Bird’s Foot. “The risks are multiplied” right now, he says over brittle murmurs from the radios—ships calling in, and Coast Guard calling out. “Down-bound traffic can’t stop, except in emergencies. Up-bound traffic has to struggle to get through the 5- or 6-knot current. Debris is floating downriver. It’s so hazardous that the upriver pilots association [between Baton Rouge and New Orleans] won’t run ships at night. So, nighttime’s pretty quiet. Daytime, anything can happen.”

A photograph on the wall shows a ship on fire. This was the Union Faith, a Taiwanese freighter that, on the night of April 6, 1969, hit a group of barges loaded with 9,000 barrels of crude oil just north of the bridge that connects downtown New Orleans to the Mississippi’s west bank. A series of explosions followed. Fire boats put out the barges before they hit the shore. A tow ship hooked the anchor chain of the Union Faith, holding it to burn and capsize in the deep part of the channel. “This collision narrowly missed resulting in a catastrophic fire on the New Orleans waterfront,” the National Transportation Safety Board reported. Twenty-five men on the Union Faith went missing and were presumed dead, including everyone on the ship’s bridge when the collision occurred. The cantilever interstate bridge 150 feet above was damaged, and it cost $10 million just to get the sunken ship out of the river. It was a clear night, and the water wasn’t high. Just an accident.

This is the worst-case scenario, though Marinelli can’t even say it before his colleagues hush him quiet. “They don’t even like to think about it,” he says. But there is good news, too. “Everybody who’s been out here for the 220-something days of high water are a lot better at their jobs now than when they started.”

What has happened down here is the weather changed. The 12 months ending in April were the wettest yearlong period in the United States going back to 1895 and caused devastating flooding across the watersheds of the Mississippi and its tributaries. This is not explicitly a product of climate change, but it does align with our long-term expectation of how the warmer atmosphere will alter—and is already altering—precipitation patterns. While parts of the Southwest and Southeast have been drier, annual total precipitation between 1991 and 2012 was up 5 to 20 percent over the historical average in most of the Mississippi watershed.

At the same time, a megalithic engineering project to tame the Mississippi, begun after the Great Flood of 1927, has pushed the river into a narrow bound relative to its historical meanderings. The river might not run at depth through New Orleans at all if it weren’t for the Army Corps of Engineers’ maintenance of the Old River Control Structure, a system of floodgates that is the subject of McPhee’s famous 1987 essay “Atchafalaya.” Old River Control ensures the Mississippi remains deep enough in Baton Rouge and New Orleans to support shipping on the lower river. Four of the country’s top 10 ports by weight are here, and they move 450 million tons of cargo every year.

Channelization has many consequences. Flooding has become more destructive when it happens, because more people live closer to the river. Un- or underguarded sections of the river are extremely vulnerable. But mostly, in Louisiana, the river stays where we put it, and the land around it slowly vanishes, deprived of the rich soil layers that once came with the floods. This is the main reason the state is losing a football field’s worth of land every 90 minutes and what looks on a map like a solid boot is in fact a shredded landscape of rapidly subsiding marshland. As Elizabeth Kolbert observes, land here not busy being born is busy dying.

Put them together and, this summer in New Orleans, channelization and climate change have helped create a river running high and fast, longer than ever before.

New Orleans is essentially an island, linked to mainland Louisiana by little more than the elevated banks of the river. This is particularly true right now: Twenty-five miles upstream of the city, the parkland that stretches five miles from the Mississippi River to Lake Pontchartrain has been submerged beneath a shimmering tongue of river water.

At the banks of the Mississippi here is the Bonnet Carré Spillway, the last possible release point to unload river water before it hits New Orleans. Built in 1931 to protect the city from a catastrophic flood, the 7,700-foot spillway (pronounced bonny carry) formalized what had been a natural crevasse during high river years. It sits just above the colossal Shell plant at Norco, a refinery and chemical plant of unfathomable scale. One structure creating climate change, one trying to manage it.

On Wednesday, Bonnet Carré set a record of its own: Most days operating in a year, at 76. This is also the first year Bonnet Carré has been opened twice, and the first year it has been open in consecutive years. (North of Baton Rouge, the Army Corps has contemplated opening the Morganza Spillway, for only the third time in its 65-year history, another sign of how extreme 2019 has been on the Mississippi.)

Along the spillway, the Big Muddy drifts against 350 bays, from each of which hangs a curtain of 20 railroad ties, or needles. To open the bays, a machine slides along the spillway track, lifting needles from their vertical position and hanging them horizontally. The structure was completed in 1931, and its mission is as simple as its design: keep the Mississippi River in New Orleans below 1,250,000 cubic feet per second. To accomplish this right now, the spillway has about half its bays open, and is releasing 147,000 cubic feet of water per second—15 Seine rivers taking the express route to the gulf.

As the years go by, it is looking more likely that high water and a hurricane could coincide in New Orleans.

From space, it is easy to see the effects of the Bonnet Carré’s big year: an enormous cloud of silt in Lake Pontchartrain and the Mississippi Sound, indicating the unprecedented influx of freshwater. “Ecologically, we’re seeing a lot more sustained damage than the BP oil spill,” Moby Solangi, the president of the Institute for Marine Mammal Studies in Gulfport, Mississippi, told the Clarion Ledger. He had counted 128 dead dolphins and 154 dead sea turtles, which he suggests were related to the lack of salinity. The effect on the fisheries has been severe, with Mississippi Gov. Phil Bryant calling for a federal disaster declaration as oysters and crabs die off.

At Bonnet Carré, there are more important concerns. Chris Brantley has been the project manager of the spillway for 13 years. He sits in an office looking out at the flooded land below, watching the carp jump from the whitewater and keeping tabs on any sturgeon or paddlefish the local fishermen catch. This is, among other things, a great place to cast. “It’s like when you go to the Grand Canyon or Yellowstone National Park, how much money you got to pay to go out there? Look at this, this is just as exciting.” We look out at the water roaring out of the milelong, concrete riverbank.

“Yeah, you’re basically saving the city of New Orleans,” I said.

“We do do that.”

Brantley has opened the spillway six times since 2008; counting the six openings before that would take you back to 1950. When I asked him if it was unusual to have opened the spillway twice in one year for the first time in its 88-year history, he displayed what I’ve come to see as classic Army Corps sang-froid. “It’s the first time it’s ever happened, but I wouldn’t say it’s unusual.”

In New Orleans, you can go days without thinking of the river. People know about the high water, but it hangs in the mind as a kind of out-of-season curiosity, like an April snowstorm in New England. The Coast Guard and the pilots wrangle and restrict ship traffic to make sure nothing big hits the shore.

Why must the Bonnet Carré keep the Mississippi at 1,250,000 cubic feet per second in New Orleans? Because that is the pressure the levees are built to withstand. Every day of the “flood fight,” when the water is above 15 feet, levee managers patrol every foot of levee searching for seepage and sand boils that indicate river water may be surfacing on the wrong side of the banks, the first indication the structure may be weakening.

Upstream from Bonnet Carré, near Baton Rouge, the river has been even higher and more ferocious. “I’ve never seen anything like it in my entire life,” 5th Louisiana Levee District President Reynold Minsky told the Monroe News Star in May. Seep water was showing up as far as a mile from the river. “I’m on pins and needles until it falls below flood stage.” Baton Rouge and Vicksburg, Mississippi, have already broken flood-stage duration records set during the 1927 flood, the disaster that prompted so much of the Army Corps’ work on the lower river.

Down in New Orleans, the levees are enormous earth-and-concrete structures, and the Army Corps of Engineers has expressed absolute confidence in them to function under extended periods of high water.

But month after month of this, year after year, puts them in uncharted territory. “Having water on [the levees] for 200 days is really testing out the flood protection system,” said David Ramirez, the chief of river engineering and water management for the Army Corps in New Orleans. He reflected on the channelized, fast-flowing river that the corps had created upstream. “The system was designed in 1928 after the big ’27 flood. It is antiquated. Is it still useful for today’s conditions? We initiated a study to start looking at that. We may be looking at the new norm.”

Rainfall flooding is a regular concern in New Orleans, since the city holds puddle points like a waffle and relies on a shaky network of pumps for drainage. Storm surge through the Gulf of Mexico and Lake Pontchartrain caused the catastrophic levee failures during Hurricane Katrina. But the river has been kept in check for a long, long time.

“There are two ways to approach the amount of water coming down,” said Natalie Peyronnin Snider, a senior director for coastal resilience at the Environmental Defense Fund. “One is trapping water in natural floodplains up north, providing space for water to go before it even gets to the river.” The other is changing the course of the lower river below New Orleans, which would both spread sediment onto subsiding coastal marshes and reduce the backup caused by the river’s tortured route to the sea. “If you shorten the distance, you can reduce the stage north of New Orleans.” (Some expensive, small-scale efforts to this effect are underway now.)

One of the most unnerving aspects of this year’s record high water is that it now coincides with the start of hurricane season. The Army Corps’ river levees are built with the assumption that tropical storms would coincide with a river only 8 feet high—less than half its present height. Hurricane Katrina pushed a surge of 13 feet up the river. Hurricane Isaac made the river run backward, with a surge of 8 feet up to Baton Rouge. A storm surge of that size right now would cause the Mississippi to overtop the levees in New Orleans, a catastrophe in its own right that would weaken the barriers below, threatening worse.

For now, that is an unlikely event that should not keep the 1.275 million people in Greater New Orleans up at night. Big hurricanes don’t typically arrive in the gulf until late August and September. A storm would have to hit the river mouth just so to cause a major river surge. But as the years go by, it is looking more likely that high water and a hurricane could coincide—and in turn, it becomes more important to rethink the logic of the system that sends so much water through New Orleans into the hot summer months.

“It’s not just the height of the water, it’s also the duration,” observed Nicholas Pinter, a levee expert at the University of California–Davis. “The longer the flood fight, the greater the threat to the levees.” He suggested that somewhere along the Lower Mississippi, the state would have to make more room for water to prevent this kind of sustained stress on the riverbanks. The river has been above 16 feet for three straight months—16 feet above sea level. Most of the city is below sea level. Ships like the Valle Azzurra float by at the end of the street like they’re flying.