“there are only two kinds of levees, those that have failed and those that will fail.”
TRANSCRIPT
“There are only two kinds of levees, those that have failed and those that will fail.”
Before KatrinaPrevious hurricane damage from less severe
storms1965- Hurricane Betsy put parts of the city
under 8 feet of water1992- Hurricane Andrew missed by 100 miles1998- Hurricane George causes billions of
dollars of damage, but it was not a direct hitDisappearance of barrier islands and
marshes due to construction
Before Katrina: Google Earth
Facts and Figures:“A hurricane storm surge can reach heights of
20 feet, but every 4 miles of marsh can absorb enough water to knock it down by one foot.”
Oil & gas exploration has accounted for 1/3 of the delta’s landloss
Coast provides 1/3 of country’s seafood, 1/5 of its oil, and 1/4 of its natural gas & harbors 40% of the nation’s coastal wetlands and provides wintering grounds for 70% of migrational water fowl
An acre of coastal wetlands disappears every 24 minutes
Fixes:Attempts to restore
marsh ecosystemCoast 2050River system on
critical areas of Mississippi
Levees to allow fresh water to escape and wash out sediments to Gulf
5000 cubic yards of sand transported to restore barrier islands
Millenium Port
Protecting New Orleans1998- $14 billion plan proposed to restore
wetlands rejected by Congress
Record sea surge of Katrina peaked at 28 feetState of the art barriers can only contain a
surge reaching 15 feetPlans for the future will improve the levees of
the city to Category 5 levelsIdeal plans would take 5-10 years to build and
cost $25-35 billion dollars
Possible PlansNot using the Army Corp of Engineers for
contractorsOuter ShieldFloating gatesSluices that slideHydraulic disksRising flaps
Grand PlanThree protection schemes:
Inner ringComprehesive planOuter shield
Delta formationForms a dynamic landscape of wetlands that
have been eroded by human activityBarrier islands evolve but human activities
speed up shrinkageIsland restoration has to be a priority to
protect the delta in the future.
Delta Formation:
After KatrinaScientists and
engineers aren’t the only ones involved in the process- stakeholder engagement
Demonstration project for other coastal regions
Investment for restoration is still being debated
Levee ConstructionArmy Corp of Engineers rebuilds after
Hurricane BetsyHigh Level option- raise all barriers to resist a
Category 3 hurricane (16-18.5 feet above sea level)
Barrier option- construct levees and gates between Lake Brogne and Lake Pontchartrain, and navigation lock, rock dike and flood control structure on Industrial Canal at Lake Pontchartrain
Impact of NEPA court case1976 lawsuit filed by Save Our Wetlands
alleged that Army Corp of Engineers FEIS (Final Environmental Impact Statement) for levee construction is inadequate and WINS.
Corp reevaluates building plan, changing from barrier to high level plan
Would the original plan have saved the city?Probably not. Levees
failed for several reasons:Insufficient depth of
pilingsUnstable underlying
soilsLax maintenance
practices
Would the original plan have saved the city?Storm surge came
from Lake Borgne, not Lake Pontchartrain
Barrier project may have exacerbated the damage by deflecting surge
Would the original plan have saved the city?MRGO
Shrinks from 2000 to 200 feet wide
Intensified storm surge by 20%
Increased velocity of surge from 3 to 6-8 feet per second
Storm Surge modelinghttp://www.nd.edu/~adcirc/katrina.htmThe first detailed computer model of Hurricane
Katrina's storm surge shows a gargantuan, 15-foot dome of water forming in the Gulf of Mexico. Propelled westward by 140-mph winds, the surge slams into levees east of New Orleans and pours over them, flooding a large inhabited area.
Later, the model shows water flooding most of the rest of New Orleans from Lake Pontchartrain through levee breaches. Meanwhile, Katrina's giant wave continues its relentless northeast course, pushing a 30-foot wave over the Biloxi-Gulfport area in Mississippi.