Time Sept. 2–9, 2019‘IT’S SINKING IN ... WHAT WE’VE
BEEN DOING FOR THE PAST
100 YEARS ISN’T WORKING.’
COLIN WELLENKAMP, EXECUTIVE DIRECTOR,
MISSISSIPPI RIVER CITIES AND TOWNS INITIATIVE
U.S. Army Corps of Engineers. An elite
military squadron founded by Thomas
Jefferson in 1802, the Corps has grown
into a massive bureaucracy, with a budget
of $7 billion in 2019 for civil works. The
Corps dug a tunnel in Alaska to study the
effects of excavating through permafrost;
it built a city in Saudi Arabia to house the
country’s troops. The MR&T Project is in
many ways the agency’s masterwork. Paul
Hudson, a hydrologist at Leiden Univer-
sity in the Netherlands, calls it “among the
largest and most ambitious engineering
feats on earth.” The Corps’ motto seems
apt: “Essayons,” French for “let us try.”
The Mississippi can be quiet and peace-
ful upstream, but amid the MR&T Project
below Baton Rouge, the water slapped and
jostled my canoe, its surface covered in
thickets of white rapids 100 acres across.
Sean Duffy, executive director for the Big
River Coalition, a maritime- industry lob-
bying group, says the Mississippi’s cur-
rent state is scary for freighter pilots too,
who cart oil and chemicals through the
heavily populated corridor. The five deep-
draft river ports in Louisiana include the
largest by tonnage in the western hemi-
sphere, and more than 500 million tons
of cargo pass through this stretch each
year. But the flood is affecting business:
when the river is high, freighters must
lighten their loads, which Duffy says can
mean leaving a million dollars of cargo
aside on a single trip. Amid the rain and
storms, it’s clear to Duffy that the climate
has changed. “Whether it’s long-term,”
he says, “I can’t answer that question.”
To scienTisTs, The answer is a re-
sounding yes. Across the U.S., the past year
has been extraordinarily rainy—nearly
8 in. wetter than usual from July 2018 to
June 2019. This fits with climate-change
predictions: a warm atmosphere holds
more moisture in the air, which can be
released suddenly, causing some re-
gions to have more rainfall and flooding.
The Big Flood, though, will not be due
to climate change alone. A paper pub-
lished in Nature last year attributed up to
three-quarters of the increase in flooding
on the Mississippi to human engineering,
especially the levees, which squeeze the
river, raising its height.
There is, too, the unpredictability
of man-made flood- control structures.
Hudson, the Leiden University hydrolo-
gist, worries that any attempt to tame a
river is a trial-and-error operation. Infra-
structure is built on a much faster time
scale than the river’s sedimentary pro-
cesses. Once engineering is installed,
the river changes— depositing new mud
here, eroding banks there—and old calcu-
lations go out the window. “You’re kind
of constantly keeping up with these un-
intended consequences,” says Hudson. It
doesn’t help that much of the MR&T Proj-
ect was designed before scientists fully
understood the science of this river’s flow.
Consider one stretch of southern Loui-
siana where three rivers—the Mississippi,
the Atchafalaya and the Red— tangle to-
gether. In the 1830s, the Corps attempted
to tame the mess, straightening the path
of the Mississippi. By the 1950s, scien-
tists noticed the consequences: more
water was going down the Atchafalaya
River, a distributary of the Mississippi.
The Corps determined that within a de-
cade, the Atchafalaya, around a tenth as
powerful as the Mississippi, might be-
come the bigger river.
That change—which remains pos-
sible today—would devastate New Or-
leans. Seawater would trickle up to fill
the emptied riverbed, putting the city at
the edge of a brackish bayou and cutting
off its access to drinking water and the
riverine highway that drives its economy.
The effects would ripple up the Missis-
sippi Valley, whose farms and refineries
depend on Louisiana ports.
The response: build more “improve-
ments,” as the Corps once dubbed its en-
gineering. In 1959, the Corps inaugurated
a new element of the MR&T Project, the
Old River Control Structure, at the in-
tersection of the three rivers. The struc-
ture is a massive complex that includes 11
steel gates, embedded in a concrete wall,
which are lifted and dropped by an over-
head crane, regulating the flow of water
from the Mississippi into the Atchafalaya,
ensuring 70% stays in the bigger river.
The thing looks straight out of the frozenNation
rebel base in The Empire Strikes Back.
A massive flood in 1973 put this sys-
tem to the test. A wall built to steer water
toward the gates collapsed; Army Corps
employees felt the structure shuddering,
and scrambled to open a floodway down-
stream to relieve pressure. The Old River
Control Structure held, but could no lon-
ger support the same capacity of water
for which it was designed, so the Corps
added a Band-Aid.
In May, I toured that Band-Aid: the
Auxiliary Structure, just downstream.
Seven concrete towers stood 40 ft. over
the riverside highway. A siren wailed, a
warning that one of six steel gates would
soon inch upward, letting just a trickle
more water through. Water slammed
against the gate, coiling into a whirlpool,
then dropping nearly 20 ft.—a man-made
waterfall from the Mississippi into the
Atchafalaya that in natural conditions
would be the same height.
The Band-Aid may not hold much lon-
ger. Yi Jun Xu, a hydrologist at Louisiana
State University, has found that the Mis-
sissippi’s bed is rising just downstream of
Old River. It’s created a pinch point that
could fill with mud during a flood, forcing
the water into the Atchafalaya once more.
The MR&T Project engineering has
not yet been pushed to its limit: one of
its four floodways has never been used.
Still, the hydrologists I spoke to agreed
that the system is unlikely to keep up with
the increasing flooding. One model sug-
gests that under worst-case scenarios for
global heating and increasing land use,
the river’s discharge—the volume of
water it carries each second—could grow
by 60% before century’s end.
“That’s crazy!” Xu says. “I doubt our
levee system would survive.”There is no way to predict when the Big
One will come, or what element of the sys-
tem might fail. But this year’s high water
signals that the Corps’ “project design
flood” is already distressingly out of date.
The engineering was designed around
discharge readings in 1927, but today, per-
haps because the flood- prevention struc-
tures have narrowed the river, the same
discharge often leads to higher water than
it did 90 years ago. In May, the Corps was
forced to open Bonnet Carré before the
discharge trigger was met because the
water had risen so high.SC
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