For all the time spent and attention monopolized in our national discussion of global warming and climate change, attention which to date has produced practically nothing in terms of concrete and substantial solutions to a demonstrable and present threat, there are two foreseeable, or more to the point practically inevitable, environmental events which directly threaten American life as we know it.
Neither has a thing to do with global warming.
The more dire, and more unavoidable, of the two is the eventual volcanic eruption of the massive caldera at Yellowstone National Park, which will ultimately threaten the survival of civilization. A supervolcanic eruption at Yellowstone might or might not be an extinction-level event, but it would certainly make much of North America uninhabitable for a protracted period of time, greatly disrupt agriculture and the global food supply and sharply curtail Earth’s ability to support human and other animal life for long enough to permanently change our global ecosystem.
But a Yellowstone event is perhaps thousands, or tens of thousands, of years away, and it carries effects of such a magnitude that we are utterly powerless to mitigate, much less prevent.
The other threat is far more immediate, and eminently more preventable, and while it doesn’t carry the gravity of a Yellowstone eruption its potential effect on the global economy can’t be understated.
Namely, that the Mississippi River, the world’s most economically significant watershed, is coming to the end of its lease and considering relocation.
Old Man River is a frightening and uncooperative beast in the best of times. It’s an alluvial river, meaning the Mississippi’s bed isn’t solid rock like, for example, the Colorado. At its bottom the Mississippi flows on top of sand and mud, and it moves that sediment hither and yon as it pleases while draining half the North American continent from western Canada to the Appalachians down into the Gulf of Mexico.
Which means every thousand years or so the Mississippi will choose for itself a new channel. And it has already chosen a preferred route to the Gulf of Mexico which differs from the one it now occupies, which takes it past Natchez, Baton Rouge, and New Orleans through to its current mouth.
That path, which measures some 345 miles from the Old River Control Structure south of Natchez to the Gulf, is more than twice as long and far less steep a decline to the sea than the Atchafalaya (pronounced uh-CHAFF-a-LIE-a) River to the west. The Atchafalaya’s course, which puts into the Gulf at Morgan City, is only 150 miles — and the Atchafalaya flows considerably more rapidly than does the Mississippi for much of that length.
Truth be told, the Mississippi would have already changed its course and become the Atchafalaya had it not been for the efforts of the U.S. Army Corps of Engineers (USACE). Starting during World War I, the Corps began taking over the efforts to build levees along the Mississippi to force it into its current path and prevent flooding — previously those levees were built by local landowners along the river and in some cases local governments, but their size and quality were almost never up to the task and flooding along the river was a constant problem.
The USACE’s initial results weren’t the best. A massive flood in 1927 overwhelmed the Corps’ levee system and rendered more than a half-million Americans homeless. Following the Great Flood, the Corps redoubled its efforts and built higher, stronger levees — and changed its management of the river to include floodways as tools to keep it under control. The Bonnet Carré Spillway, located 30 miles upriver from New Orleans, was built in 1931 to release water from the Mississippi into Lake Ponchartrain, and the Morganza Spillway, located about 34 miles northwest of Baton Rouge, went into service in 1954 to allow flood waters to spill from the Mississippi into the Atchafalaya basin. A few years later, in 1963, the Old River Control Structure (ORCS), the USACE’s pride and joy along the lower Mississippi Valley, was built just above the Morganza Spillway.
The ORCS is one of the more unsung, but fascinating, pieces of critical infrastructure in the entire United States. It’s located where the Red River and Mississippi meet, and it’s where in the early 19th century a man-made engineering achievement set the stage for the current hydrologic drama. In 1839, Captain Henry Shreve completed a commission by the federal government to clear what was known as the Great Raft, a 150-mile logjam of dead wood collecting in the Red River which prevented it from being navigable. Eight years earlier, Shreve had also cut a canal through a large meander bend of the Mississippi at the current Old River site, shortening the Mississippi for navigation by 18 miles and creating an outlet for the Mississippi into the Atchafalaya, which prior to the 15thcentury was actually the lower part of the Red. The USACE recognized the threat of the Mississippi changing its course by the 1950s and called in some of the world’s best hydrologists and engineers to combat the problem.
One of whom, interestingly enough, was a hydraulic engineer from Cal-Berkeley named Hans Albert Einstein, son of the famous scientist. Einstein helped design the ORCS’s initial Low Sill and Overbank structures, which have as their object the regulation of the flow of the Mississippi and Atchafalaya — the lower Mississippi is to receive 70 percent of the combined flow of the Red and Mississippi above the ORCS, while the Atchafalaya the remaining 30 percent. The Low Sill structure is essentially a 566-foot-long dam with 11 gates, each 44 feet wide, that could be raised or lowered to control the amount of flow leaving the Mississippi.
But the Low Sill nearly failed during a massive flood in 1973, as the Mississippi scoured out a giant hole in its base. Massive flood damage was averted by opening the Morganza Spillway, but the river came perilously close to jumping its banks, destroying the control structure and charting its new course. A terrific book on that event is James Barnett, Jr.’s Beyond Control: The Mississippi River’s New Channel to the Gulf of Mexico, published in 2017. It tells the story of the near-failure of the ORCS, as summarized by Weather Underground founder Dr. Jeff Masters in an excellent series of blog posts on the Mississippi’s potential course change…
… the Old River Control Structure foreman walked out on the Low Sill Structure for an inspection, and witnessed the collapse of a 67-foot-long wall along the south side of the intake channel, facing the Mississippi. The six Niagara Falls’ worth of water pouring through the channel pulverized the wall’s fragments and rammed them through the structure. A giant whirlpool replaced the missing wall and began attacking the structure, scouring away at the 90-foot deep steel pilings that supported it. The foreman reported that you could drive out onto the highway that crossed the structure, open your car door, and the vibration from the water hammering through the structure would close the door for you.
A camera was lowered down a hole drilled down through the center of the structure. The camera showed fish where there should have been solid earth. The river had begun scouring out a football field-sized hole over 50 feet deep underneath seven of the low sill’s eleven gate bays. The scour hole came within 150 feet of a second, even-larger scour hole which had developed on the downstream side of the gates. Had the two scour holes merged, the entire structure would have been undermined and failed.
It’s the kind of thing you’d expect in a disaster movie, only it was real. The USACE commandant in charge of fighting floods at the time, Major General Charles C. Noble, ordered the Morganza Spillway opened just two days later and averted a major crisis. It was the first time that Morganza had opened since its construction; downriver, the Bonnet Carré Spillway first opened in 1937 and had been put into use often. (Bonnet Carré has been opened twice this year and it’s open now.)
USACE then set to work beefing up the ORCS, adding an Auxiliary Structure in 1986 to help alleviate the pressure on the Low Sill Structure, and then in 1990 adding the Sidney A. Murray Junior Hydroelectric Plant. It appeared at the time that the ORCS had won the battle over the Mississippi.
But what the Corps wasn’t paying sufficient attention to was the Mississippi’s next move.
The Mississippi, as mentioned above, is an alluvial river. It carries with it an incredible amount of sediment — and it’s not overly tidy about where it leaves all that mud. So while the Corps had the Mississippi reined into its current path to the Gulf, that sediment kept accumulating inside the river’s levees.
And when another massive flood event struck in 2011, the Corps was forced to open the Morganza Spillway again. While there was less danger of the ORCS failing this time, scientists studying the river began to notice with alarm that the Mississippi was essentially building siege engines to defeat mankind’s fortress along its banks, and the ORCS is the chief battlefront in the war.
A 2017 paper by hydrologist Yi-Jun Xu of Louisiana State University sounded a major alarm over the fact that the Mississippi’s river bottom at Red River Landing, a few miles downriver from the ORCS, had been rising rapidly due to sediment buildup — so much so that it reduced the river depth by about 30 feet and narrowed the channel by half a mile since 1985.
Xu estimated the sediment building at some 36 million metric tons, and contended that it greatly increases the possibility a future “mega flood” could overwhelm the ORCS and trigger a full river course change into the Atchafalaya. Xu also noted the presence of some 30 sand bars from Vicksburg, Mississippi to the ORCS having accumulated more than 530 million metric tons of material — and warned that in a major flood event those sand bars could be dislodged and swept downstream, with highly unpredictable effects. Perhaps that sediment might accumulate in the rising river bottom downstream and accelerate a river course change, or perhaps it might cause even more dramatic scouring at the ORCS facilities — making 1973 a mild event.
So what would it mean if the Mississippi did become the Atchafalaya? What if a major flood event overwhelmed the ORCS and changed the river’s course? How bad would that be?
Bad, is your answer. Catastrophically so.
Understand that 60 percent of America’s grain exports flow through the four ports on the Mississippi between Baton Rouge and its mouth, and all four would be closed to river traffic in the event of a course change. Those four ports — the ports of South Louisiana (located between New Orleans and Baton Rouge), New Orleans, Baton Rouge, and Plaquemines (near the river’s mouth) rank as #1, #5, #9 and #14, respectively, in all of North America by tonnage. Were all to close America would have no ability to export agricultural products to world markets in the volume we currently do — meaning the failure of our nation’s agricultural sector and a worldwide famine which isn’t fixable in the short term. Yes, port facilities could be built along the Atchafalaya, but that would take years — and the wild scramble that the Atchafalaya would become after absorbing three times its current flow would make it one of the more dangerous waterways in the world to navigate.
And the port at the Atchafalaya’s mouth, Morgan City, is an exceptionally low-lying area with a population of 12,000 people. A rapid course change of the Mississippi would all but surely not just inundate Morgan City but the force of all that current could well carry much of it out to sea.
Then there is the demise of a giant chunk of America’s petrochemical industry which sits between Baton Rouge and New Orleans; without the freshwater access and navigability of the Mississippi those oil refineries and chemical plants would become largely unusable without major retrofitting, leading likely to much of the nation’s industrial capacity going onto the world market for potential relocation.
And there are the 1.5 million people in the greater New Orleans area left without drinking water, who would then have to evacuate. Let’s remember that the Mississippi’s river bottom south of Baton Rouge is below sea level. The only thing keeping the lower river from becoming a tidal saltwater estuary is the massive flow of water from half the continent pushing the Gulf of Mexico away; if the Mississippi changes its course, the Gulf will come pouring in and poison the drinking water for one of the nation’s major metropolitan areas.
Those are just some of the highlights of the national and global economic calamity we’d face.
Obviously, this can’t be allowed to happen. No matter how massive an effort it takes to shackle Old Man River to his current path, it’s cheap compared to the multi-trillion dollar disaster a course change would mean for the national and world economy.
So what’s the answer?
For one thing, Congress has begun taking a long look at the USACE’s management of the river and wants a more aggressive stance taken to combat the sedimentation of its lower section. The Water Resources Development Act (WRDA) of 2018 addresses a number of key items within the Corps’ purview. Among them are reforms to how the Corps handles dredging operations on major waterways, including the Mississippi, and paving the way for more private contracting to conduct dredging more cheaply, and perhaps most importantly to take a new look at the Corps’ management of the ORCS. From a press release on the WRDA after its House passage by Louisiana congressman Garret Graves, who has led congressional efforts to change the USACE’s river management strategy…
The current strict requirement that 70 percent of the flow go down the Mississippi River while 30 percent go down the Atchafalaya River is antiquated and misses opportunities to advance flood protection, coastal restoration, our ports, fisheries and crawfish production, hydroelectric production and other benefits. Current law has the Corps operating such structures based on 70-year-old conditions.
Later this year the Corps is slated to produce its own plan for reforming its river management, and specifically with respect to the Old River facility, as required by the WRDA.
But in the meantime, sometime next week the Morganza Spillway is slated to open again for only the third time in its existence — in response to what the USACE is calling a “historic and unprecedented” flood event. River levels in the Mississippi are perilously, frighteningly high — and at the gates of the Morganza Spillway the water is only a few feet from overtopping the facility.
There is no expectation the long-feared disaster is upon us. Not this time. But with that rising river bottom and the Mississippi’s increased flow thanks to increasing urbanization upriver (paved surfaces mean water drains far more rapidly from the land) and other factors, the challenge and the threat are only increasing. And the Corps’ talents and resources to keep Old Man River in line had better be up to the task.
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