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A28 SCIENCE
Saturday 17 auguSt 2019
Flooded Mississippi a threat as hurricane season heats up

By JEFF MARTIN and JANET 20 feet (6.1 meters) deep
McCONNAUGHEY in places. "I would assume
Associated Press major problems on the river
NEW ORLEANS (AP) — The if we had a high river with a
river that drains much of Katrina event," said Jeffrey
the flood-soaked United Graschel, with the National
States is still running higher Weather Service's Lower
than normal, menacing Mississippi River Forecast
New Orleans in multiple Center.
ways just as the hurricane The vast majority of the
season intensifies. $14.6 billion spent on flood
For months now, a massive controls as a result of Ka-
volume of water has been trina went not to the river
pushing against the levees levees, but to shore up and
keeping a city mostly be- block areas that failed.
low sea level from being The possibility of a punish-
inundated. The Mississippi ing storm surge meeting a
River ran past New Orleans swollen Mississippi in New
at more than 11 feet (3.4 Orleans is a different threat,
meters) above sea level for one that could become
a record 292 days, drop- more common as the plan-
ping below that height only et warms, spawning longer-
Monday. lasting floods and earlier
"The big threat is water In this May 10, 2019 file photo, workers open bays of the Bonnet Carre Spillway, to divert rising hurricanes.
getting through or under- water from the Mississippi River to Lake Pontchartrain, upriver from New Orleans, in Norco, La. Barry was the first hurricane
neath," said Nicholas Pinter, Associated Press to menace when the river
an expert on river dynamics was as high as it was in July,
and flood risks who's stud- fident that South Louisiana ing high water, dangerous ter for Coastal Resiliency. Boyett said.
ied levee breaches across river levees are in great seepage gets stopgap For most of the past three In 1929, the year construc-
the nation. "The longer the condition, with improve- coverage: About 63,000 decades, the Mississippi tion started on the spillway
duration, the greater the ments made since 2011. large sandbags have been has run about 3 to 5 feet (1 that caps the river's height
threat." "If there's a silver lining go- used since March on one to 1.5 meters) high in mid- at New Orleans, the Missis-
Locals walked up levees ing into hurricane season 300-foot-long (91.5-meter- August at New Orleans' sippi topped at 19.99 feet
from Baton Rouge to New with the river this high for long) seepage area upriver Carrollton gauge. The last (6.1 meters) in June, Boyett
Orleans to see the river this long, we're entering the of Baton Rouge, he said. time it was this high was said. But that year saw only
for themselves as Tropical hurricane season having Even so, experts who study 11.4 feet (3.5 meters) in Au- five Atlantic tropical sys-
Storm Barry briefly men- done 200 inspections of the flowing water say there's gust 2015, a year when no tems, with two hurricanes
aced Louisiana last month, levee since February," Boy- a risk the river could rise significant tropical weather in the Gulf, National Hur-
but the real damage runs ett said. above the tops of some reached Louisiana's coast. ricane Center data show
underneath, experts say: Inspectors were looking for levees in the New Orleans It was 12.2 feet (3.7 meters) — and both stayed away
All that rushing floodwa- parked barges, stuck debris area, if a hurricane pushes in 1993, another year Louisi- from Louisiana. NOAA fore-
ter can scour levees along or other potential trouble, enough storm surge up the ana's coast escaped harm. casters now expect 10 to
their foundations, causing such as tire ruts or damage swollen river. The city's le- When Katrina formed as a 17 named storms this year,
damage in places that from feral hogs on grassy vees held the river back in tropical storm in the Baha- including five to nine hurri-
can't easily be seen. surfaces. They also looked the great flood of 1927 and mas on Aug. 24, 2005, the canes.
"That ultimately could un- for water seeping through, haven't been topped since river stage in New Orleans Opening spillways upriver
dermine the levee as well and for sand boils — spots then, Boyett said. was just 2.44 feet (0.74 me- from New Orleans can't fix
and cause a breach or a where water tunneling be- A Category 4 hurricane ters) above sea level. It rose this, because they were
failure," said Cassandra low a levee seems to bub- striking the Louisiana coast- to 3.6 feet (1.1 meters) the designed to keep water
Rutherford, assistant profes- ble out of the ground. line can produce a 20-foot day before Katrina devas- flowing at a manageable
sor of geotechnical engi- Concrete mats armor un- (6.1-meter) storm surge , tated the city in 2005. rate, not to quickly drop
neering at Iowa State Uni- derwater areas likely to be the National Oceanic and Katrina knocked out an au- river levels, which could
versity. eaten away by the river's Atmospheric Administra- tomatic station that would cause mudslides when le-
The federal agency that current, Boyett said. Sand tion says. However, that have measured peak surge vees don't dry out as fast as
maintains the levees is boils get ringed with sand- surge's size at New Orleans, at the river's mouth, but the water falls, Boyett said.
aware of the risks. But Ricky bags until the water pres- more than 100 winding riv- an analysis by the Federal The changing climate
Boyett, spokesman for the sure on both sides equal- er miles up from the coast, Emergency Management means this problem could
New Orleans office of the izes, stopping the flow. And would be reduced by the Agency indicates the surge become an annual threat.
U.S. Army Corps of Engi- because some permanent Big Muddy's push seaward. reached nearly 28 feet at "Flooding is never a one-
neers, said the corps is con- repairs can't be made dur- The levees range in height Pass Christian, Mississippi. time thing. We're just wait-
from 20 to 25 feet (6 to 7.5 Surge pushed the Missis- ing for the next one," said
meters). While river levels sippi River up to 11.6 feet Pinter, an associate di-
are finally falling, the Na- (3.5 meters) at New Or- rector of the University of
tional Weather Service leans — not a threatening California Davis Center for
projects the Mississippi will height with the river low. Watershed Sciences. "Giv-
remain above average at But surge from the brack- en model predictions for
New Orleans as hurricane ish lakes to the city's north climate change and rising
season heats up. and east reached 19 feet sea levels and suggestions
"We really have a height- (5.8 meters), overtopping that hurricanes are may-
ened concern this year," or breaching those levees be getting more intense,
said Scott Hagen, of Louisi- and flooding 80% of the it's something we have to
ana State University's Cen- city with water as much as keep an eye on."q