Hurricane George’s flood threat to New Orleans

World TradeCenter: 13.4 fee

ClaiborneAvenue:0.5 feet

Lake Pontchartrain levee:14.5 feet above sea-level

METAIRIE RIDGE

HarrisonAvenue:-3.6 feet

FilmoreAvenue:-4.9 feet

Robert E. LeeBoulevard:-3.5 feet

Lake PontchartrainBroadStreet:-0.3 feet

CarrolltonAvenue:-1.2 feet

Base ofI-610:-2.8 feet

Cemeteries atCity Park Ave.: 3.9 feet

Mississi21.4 fee

Normal lake level:1 foot above sea level

54

31

Surge crashes inlandwith high wind-drivenwaves on top

FRENCH QUARTERMID-CITYLAKEVIEW

SEA-LEVEL

CANAL BLVD.CANAL STREET

Jeff DavisParkway:-1.8 feet

GalvezStreet:0.6 feet

RampartStreet:2.3 feet

BourbonStreet:2.5 feet

NavarreAvenue:1.9 feet

PolkStreet:-4.6 feet

JewelStreet:0.9 feet

Over 8 feet

4-8 feet4-8 feet

Less than 4 feet

No floodingat UNO

Intracoastal Waterway

ChefMenteurPass

Rigolets

PearlRiver

LakeBorgne

Lake Pontchartrain

Lac des Allemands

Lake Salvador

Lake Cataouatche

Lake Lery

Mississippi River

Miss

issi

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iver

WEST BANK

ST . BERNARDPARISH

9TH WARD

EASTERNNEW ORLEANS

NEW ORLEANS

HARAHAN

META IR IEKENNER

NORCO

LAPLACE

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Mississippi River-Gulf Outlet

CANAL STREET

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Lake Pontchartrain

Much of the area is belowsea-level, creating a natural“bowl.” Storm surge simplyfollows the law of gravityand meanders to thelowest points.

Mississippi River

CAUS

EWAY

VETERANS MEM. BLVD.

W. ESPLANADE AVE.

WILL

IAM

S BL

VD.

AIRLINE DR.

K E N N E R

M E T A I R I E

A L G I E R S C H A L M E T T E

W E S T W E G O

CLEARVIEW PKW

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METAIRIE ROAD

HAYNE BLVD.

CHEF MENTEUR HWY. Ÿu90

CARROLLTO

N AVE.

ESPLANADE AVE.

ST. CHARLES AVE.

DAVID DR.

JEFFERSONHWY.

GEN. DE GAULLE DR.

WEST BANK EXPWY.LAPALCO BLVD.

Cross-section ofstreets below

BULLARD AVE.

READ BLVD.

PARI

S RO

AD

CROWDER

BLVD.

W. JUDGE PEREZ DR.

ST. BERNARD HWY.

GENTILLY BLV

D.

FRANKLIN AVE.

LOUISIANA AVE.

EARHART EXPWY.

TERRY PKWY.

A R A B I

Intracoastal Waterway Miss. River-Gulf Outlet

Mississippi River

H A R A H A N

H A R V E Y

G R E T N A

E A S T E R NN E W O R L E A N S

N E W O R L E A N S

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MAGAZINE

BELLE CHASSE HWY.

4TH

KEY:5 feet or more above sea-level0 to 5 feet above sea-level0 to -5 feet below sea-level-5 feet or less below sea-level

Jefferson

St . C

ha r l e s

O r l e a n sJ e f f e r s o n

P l a q u e m i n e s

O r l e a n s

S t . B e r n a r d

O r l e a n s

EXPLAININGTHE BOWL

When a hurricane even stronger than Georges hits New Orleans, Lake Pontchartrain — a foot higher than sealevel — will be the city’s biggest threat. Surge water from the Gulf of Mexico, topped by towering waves, willswell the lake above levees and cause widespread flooding. A look at average surge levels by category, comparedto a cross-section of the city known as “the bowl”:

CITY BELOW THE SEA

Surge and wavesat low tide*

HurricaneCategory

7 feet

14 feet

24 feet19 feet

9 feet12345

Effect on New OrleansLake Pontchartrain’s levees stop the low-level surge

Levees stop bulk of surge, but waves could cause considerable flooding

Entire city submerged including Mississippi River leveesLevees topped, causing catastrophic flooding

Levees stop the surge, but some waves could find their way over

SL IDELL

MANDEV ILLE

Note: Figures correspond to maximum surge heights, plus Lake Pontchartrain’s +1 sea-level. High tides could add as much as 2 feet, and the surge level could rise even higher in some spots on the lake’s shore. Elevations are approximate. Source: LSU’s Louisiana Water Resources Research Institute, Army Corps of Engineers, staff research

Over 8 feetOver 8 feet

Dry land onMetairie Ridge

UNDER

Approximate floodingdepth corresponds tosatellite image above

2

Approximatediameter ofhurricane’s eye

New Orleans most recently dodged catastrophicflooding in 1998, when Hurricane Georges cutacross the Gulf of Mexico on a beeline to themouth of the Mississippi River. As half thepopulation fled, the storm veered tothe east and made landfall in Mississippi.The hurricane caused flooding inSt. Bernard Parish and also pushedwaves from Lake Pontchartrainup against its south shore levees,leaving many to ponder:What if?

IF GEORGES HADN’T TURNED

5 ST. CHARLES SUBMERGEDHere, water in the lake would reachheights of 3-8 feet above normal, spillinginto wetlands and towns in St. Charlesand St. John parishes. The water wouldbe deepest near the river levees.

6 GRAVITY’S GATEWAYRelentless winds from the stalled hurricanepush a dome of water 14 feet above sealevel at the levee. The model says that waterwould top low levees and floodwalls andmove east into Jefferson and Orleansparishes. Jefferson Parish officials say someareas would be sandbagged to 10 feet butprotection would be lower near the river.

7 FILLING THE BOWLWith the storm stalled, water continues to pourinto Jefferson and Orleans, filling the bowl withas much as 8 feet of water until it reachesnatural ridges or the Mississippi River levees.

90°W 89°W 88°W

30°N

29°N

28°N

27°N

26°N

87°W 86°W 85°W

L A .

M I S S . A L A . G A .

F L A .

Gulf of Mexico

ModelGeorgespath

Sept. 26 at 4 a.m.

ActualGeorgespath

50 miles

1 THE MODELA computer model designed by LSUscientists Joseph Suhayda and VibhasAravamuthan and used by governmentagencies to prepare evacuation plans showswhat would have happened if Georges hadnot turned. This scenario assumes that thestorm continued on the track and intensityforecast by the National Hurricane Centeron Saturday, Sept. 26, 1998, at 4 a.m. In themodel, Georges intensifies to a Category 3with 115-mph winds when it makes landfalljust west of the mouth of the Mississippi.During the next two days, it moves slowlynorthwest, weakening to a Category 1 andstalling over eastern New Orleans.Here’s what would happen ...

4 LAKE LEVEES HOLDWinds on the west side wouldpush water against thehurricane-protection levees.

3 SLIDELL SOAKEDLarge parts of Slidell wouldbe inundated, but the waterswould recede rapidly with nolevees to contain them.

L A .

MISS. A L A .

New Orleans

F L A .

Gulf of Mexico

100 miles

HLakePont.

Clockwise high-pressure winds

Counter-clockwisehurricanewinds

Windspushingwaterinto lake

Easterly winds in advance of the storm would pumpwater from Lake Borgne and from Breton andChandeleur sounds into Lake Pontchartrain, raisingthe lake’s surface by 5 feet.

2 PUMPED UP LAKE

ELEVATIONS

CLEARY AVE.

TRANSCONTINENTAL DR.

BROAD

ELYSIAN FIELDS AVE.

ROBERT E. LEE BLVD.

KEY:Surge water flowWind directionModel hurricane track