Atchafalaya

The New Yorker, February 23, 1987 (the web page carries the date February 16), by John McPhee. Subtitle: “The struggle to maintain the Mississippi River.” Later the first part of McPhee’s book The Control of Nature (1989).

One-line: The Mississippi is trying to change course into the Atchafalaya, as it does about once a millennium; the U.S. Army Corps of Engineers has been ordered to stop it, and McPhee walks through the structure, the history and the people to show how uncertain that fight is.

Saved because BuccoCapital Bloke called it “one of the finest essays every written” (I’ll never pass up an… (tweet), October 2026). Read in full 2026-10-26.

The problem

• How deltas work. The Mississippi built southern Louisiana by jumping within a 200-mile arc “like a pianist playing with one hand.” As the mouth advances, the gradient flattens, sediment builds up the bed, and the river spills toward a steeper route. Major shifts came roughly once a millennium: Bayou Teche was the main channel 3,000 years ago, then a course to the east, then Bayou Lafourche (2nd century AD), then the present Plaquemines route (from about AD 1000).
• The next shift was due. The Atchafalaya reaches the Gulf in 145 miles, under half the Mississippi’s route, with a three-to-one slope advantage. Since about 1860 it took more of the Mississippi every decade: about 30% by 1950. Geologists predicted around 1950 that the capture would be unstoppable by 1975.
• What capture would mean. Baton Rouge and New Orleans left on a tidal creek; New Orleans’ harbor a silt bar and its fresh water gone; the riverside petrochemical belt (du Pont, Exxon, Shell, Dow, Monsanto and others — “the American Ruhr”) stranded. “Nature, in this place, had become an enemy of the state.”
• Old River is the 7-mile crosspiece of an “H”: the Mississippi on the right, the Atchafalaya and the Red River (captured by the Atchafalaya in the 1940s) on the left. Water poured out of the Mississippi through it, at times enough to “quintuple the falls at Niagara.”

The fix: Old River Control (1963)

• Authorized 1954. The Corps cut Old River with a 100-foot-high, five-million-ton earth dam, added a navigation lock, and built a 566-foot “low sill” control structure with eleven gates, fed by a new channel.
• Congress ordered the 1950 ratio preserved forever: 30% of the combined flow to the Atchafalaya. The Corps could not simply shut the Atchafalaya — it was the safety valve for floods and the water source for the Cajun swamps, towns and farms — so it had to give the river some water while stopping it taking all. McPhee: a “Fort Laramie” for a river.
• General Thomas Sands: “what we’ve done here at Old River is stop time.”

1973: the structure nearly fails

• High water for weeks, at more than two million cubic feet a second. The structure vibrated so hard that, in the operator LeRoy Dugas’s words, you could open a car door on it “and it would close the door.” LSU hydrologist Raphael Kazmann walked out on it and drove away.
• A fisherman told Dugas the guide wall had moved; it slid into the inflow channel and broke. A scour hole “larger and deeper than a football stadium” had formed on the outflow side; with bedrock 7,000 feet down, the structure stood on steel H-pilings over water-filled cavities. When the Corps drilled down afterward and lowered a camera, “They saw fish.”
• More than a third of the Mississippi went down the Atchafalaya; had the structure toppled, about 70% would have. The Corps opened the Morganza Floodway for relief.
• Aftermath. Grouted and riprapped; the safe head between the two rivers cut from 37 feet to 22 (“the humor in the phrase ‘Old River Control’”). A survey boat sounds the bed five times a week (in 1974 it took 185,000 tons of rock to fill three holes). A $300 million Auxiliary Structure followed, built from a model at Vicksburg; the total cost reached about $500 million against the original $86 million.

How the river got here: three centuries of control making it worse

• New Orleans was founded in 1718, months before a great flood. Levees (3 feet in the 1720s) grew with every flood; by 1828 they were continuous in southern Louisiana. Distributaries were sealed one by one (Bayou Manchac 1828, Bayou Plaquemine 1868, Bayou Lafourche 1904).
• Henry Shreve’s 1831 cutoff created Old River and sped the Atchafalaya’s capture; clearing the 30-mile Atchafalaya logjam (broken open by the 1863 flood) and the Red River raft hurried it further. “The interventional skill of human engineers, which would be called upon in the twentieth century to stop the great shift at Old River, did much in the nineteenth to hurry it up.”
• The 1850 Swamp Act gave states millions of acres of floodplain swamp to sell for levee money; buyers drained it and demanded more levees.
• The Mississippi River Commission (1879, including Benjamin Harrison and James B. Eads) held to “levees only” for 48 years, on the theory that a confined river scours its own channel. Eads’s jetties at the mouth seemed to prove it; Mark Twain doubted the commission could “bully the Mississippi into right and reasonable conduct.”
• 1927 flooded 26,000 square miles and destroyed every bridge from Cairo to the Gulf; New Orleans was saved by dynamiting a levee. It was not a record volume — “a form of explosion, achieved by the confining levees.” The 1928 Flood Control Act ($300 million) began the Mississippi River and Tributaries Project (~$7 billion): spillways (Bonnet Carré, 1931), floodways, cutoffs, tributary dams, levees up to 30 feet, all sized to a 3-million-cfs “Project Flood.”
• Upstream development keeps speeding runoff toward Louisiana: the 1973 flood came from rain only about 20% above normal yet set a record crest at St. Louis.

The cost of holding the line

• The delta is sinking. Before about 1900, floods laid down enough sediment to offset subsidence. Now the sediment is shot off the continental shelf (356,000 tons a day); Louisiana loses more than 50 square miles a year and has lost a million acres in a century. Oil-and-gas canals (10,000 miles) and the “Mr. Go” shipping canal widen on their own and eat the marsh; a mile of marsh cuts a storm surge by about an inch.
• New Orleans is half below sea level; the river runs through it “like an elevated highway,” every drop of rain must be pumped out, and pumping speeds subsidence. Income tracks elevation.
• Everyone lobbies the Corps. Crawfishermen want more water, shrimpers less; farmers, ports, oyster beds, refineries and levee boards all pull against each other. Because the flow is now metered, there are 2.9 million potential complainants: the Corps “has been conceded the almighty role of God.”
• The Atchafalaya swamp is walled in like a zoo, silting up, and dependent on decisions at Old River; crawfisherman Mike Bourque suspects the “30%” figure. Morgan City sits behind a 22-foot seawall at the end of the floodway’s “funnel with a spout”; former mayor Doc Brownell once sank a 1,500-ton barge in Bayou Chene, without authority, to hold back the 1973 water.

The verdict

• The Corps is officially certain. Chief engineer Fred Chatry: “The Corps of Engineers is convinced that the Mississippi River can be convinced to remain where it is.” A Corps general told legislators the Corps could make the river “go anywhere the Corps directs it to go.”
• Almost nobody else is. LSU’s 1980 study gave the victory to the river, “simply a matter of time.” Kazmann calls the system “planned chaos.” The Washington Post (1980) would “bet on the river.” General Sands himself: the structure “was put in the wrong place. It was designed to a dollar figure.” District geologist Fred Smith, privately, thinks the river may divert. Dugas, asked how long the new rock armor will last: “Two high waters.”
• The essay ends with Kent, the picket boat on 24-hour watch for runaway barges, which could block the gates and build a fatal head (barges did so in 1964 and 1965). “Significant thanks to Kent.”

Notable quotes

Whenever you try to control nature, you’ve got one strike against you. — LeRoy Dugas

Mother Nature is patient. Mother Nature has more time than we do. — Jorge Cano, river pilot

She has nothing but time. — Norris Rabalais, lockmaster

The Corps had attacked Antaeus without quite knowing who he was.

Society required artifice to survive in a region where nature might reasonably have asked a few more eons to finish a work of creation that was incomplete. — Albert Cowdrey, Land’s End, quoted by McPhee

How it connects

• Civil Engineering and Infrastructure — the canonical long-form account of a structure whose failure would remake a region.
• Flood — the 1927 and 1973 floods as the turning points in flood-control policy.
• Louisiana Purchase — the Army officer who took possession in 1803 already predicted the Mississippi would find “a much nearer way to the Gulf.”
• John McPhee — author; I’ll never pass up an… (tweet) — the recommendation that put it in the wiki.