William Locke Bozeman, MT Understanding KATRINA 8/29/05

On promontories, not bays On promontories, not bays 2 category 5s, 7 cat. 4s 2 category 5s, 7 cat. 4s

History ( ) gov/pastall.shtml South Florida = most frequent South Florida = most frequent South Texas and Miss. Delta = second South Texas and Miss. Delta = second Katrina Katrina Rita Rita Percent per year probability (historical) per 50-mile (80 km) coastline

Hurricane history Cat. 3+ Hurricanes Named storms

Hurricane history Cat. 3+ Hurricanes Named storms But – see emanuel/anthro2.htm emanuel/anthro2.htm

Kerry Emanuels’ Nature discussion Nature discussionNature discussion The Power Dissipation Index is a measure of the energy associated with hurricanes, and is calculated from the velocity cubed times the area affected (size times persistence). The Power Dissipation Index is a measure of the energy associated with hurricanes, and is calculated from the velocity cubed times the area affected (size times persistence). 70% increase since % increase since 1974 Note ENSO cyclicity! Note ENSO cyclicity! ftp://texmex.mit.edu/pub/emanuel/PAPER S/NATURE03906.pdf

Miss. delta Sea level? Sea level? –Lake Pontchartrain –Lake Borgne –SW Pass SW PASS

Mississippi delta in flood Note: Note: –Sediment to Gulf 1,000,000 ton/day –Flooded outer delta –Dry diked areas –Vegetation/land use on natural levees Bayou Lafourche

Topography of New Orleans Much of north N.O. lies well below sea level Much of north N.O. lies well below sea level Sea water gains access through canals Sea water gains access through canals An uneasy truce is maintained by ~350 miles of levees. An uneasy truce is maintained by ~350 miles of levees. From Brian Hayes (2005), American Scientist, v. 93, p [original map from Louisiana State University]

Natural levees Result from multiple floods Result from multiple floods Extend 2+ km from river channel Extend 2+ km from river channel Are poorly engineered! Are poorly engineered!

Which way to the ocean? Miss. R. is twice as long (half as steep) as shortcuts via the Atchafalaya R. or Lake P. Miss. R. is twice as long (half as steep) as shortcuts via the Atchafalaya R. or Lake P. Atchafalaya Mississippi

Mississippi River deltas Sea level stable for ~6000 yr Sea level stable for ~6000 yr Delta front moves as river avulses Delta front moves as river avulses Average duration <1000 yr Average duration <1000 yr Modern delta for ~1300 yr Modern delta for ~1300 yr Time for a change! Time for a change!

Recent sediment thickness Greatest near edge of shelf [max. ~ 100 m] Greatest near edge of shelf [max. ~ 100 m] Can’t restore wetlands Can’t restore wetlands Can’t armor coast Can’t armor coast Can compact and subside (1-10 mm/yr)! Can compact and subside (1-10 mm/yr)! S.L.  1-3 mm/yr S.L.  1-3 mm/yr N.O. -8’ to 15’ “above” sea level. N.O. -8’ to 15’ “above” sea level.

Levee history & failure Overtopping Overtopping Seepage through/under the levee Seepage through/under the levee Not protection - postponement Not protection - postponement Courtesy USACOE

Katrina

Sea-surface temperatures Note extremely warm water Note extremely warm water Shallow coastal waters commonly lack cold layers Shallow coastal waters commonly lack cold layers Image courtesy NASA-JPL

Intensification Warm surface water alone was insufficient Warm surface water alone was insufficient Dynamic water topography shows a deep warm current Dynamic water topography shows a deep warm current (Also briefly strengthened Rita, later) (Also briefly strengthened Rita, later) Scharoo et al., Eos, v. 86 (40), p. 366.

Katrina by strength and warnings Tropical depression Tropical depression Tropical storm Tropical storm Hurricane 1 Hurricane 1 Hurricane 2 Hurricane 2 Hurricane 3 Hurricane 3 Hurricane 4 Hurricane 4 Hurricane 5 Hurricane 5

Katrina winds

Katrina modeled rainfall Note max. EAST of track of storm eye Note max. EAST of track of storm eye Same for wind Same for wind

Hurricane Structure Cyclonic (CCW) winds >74 mph Cyclonic (CCW) winds >74 mph Right side = storm wind + forward motion Right side = storm wind + forward motion Left side = storm wind – forward motion Left side = storm wind – forward motion N.O. Waveland Biloxi

Storm surge Key variables Key variables –Onshore winds –Central pressure –State of the tide –Configuration of the coast Can exceed 8 m (25’) in worst case scenario Can exceed 8 m (25’) in worst case scenario

Katrina comes ashore [Surviving] tide gauges [Surviving] tide gauges

Katrina storm surge (model hindcast) It missed New Orleans It missed New Orleans Max. impact on Miss. Coast Max. impact on Miss. Coast Funneling? Funneling?

Flooding at New Orleans Observed at Miss. River gauge Observed at Miss. River gauge Not (quite) to flood stage ~12 foot storm surge Not (quite) to flood stage ~12 foot storm surge Big sigh of relief as storm passed but… Big sigh of relief as storm passed but…

Images courtesy NASA

Biloxi Biloxi Pass Christian Pass Christian Damage (courtesy of USGS)

Most intense RankHurricaneYear Category at landfall Minimum Pres. (mb) Minimum Pres. (in) 1(FL Keys) Camille (MS, SE LA, VA) Andrew (SE FL, SE LA) (Indianola TX ) (FL Keys, S TX) (Lake Okeechobee FL) Donna (FL, Eastern U.S.) (New Orleans LA) Carla (N & Cent. TX) LA (Last Island)

Costliest RankHurricaneYearCategoryDamage 1Andrew (SE FL, SE LA) Charley (SW FL) Ivan (AL/NW FL) Frances (FL) Hugo (SC) Jeanne (FL) Allison (N TX)2001TS5 8Floyd (Mid-Atl & NE) Isabel (Mid-Atlantic) Fran (NC)

Deadliest (through 1996) RANKINGHURRICANEYEARCATEGORYDEATHS 1.TX (Galveston) FL (Lake Okeechobee) FL (Keys)/S. TX NEW ENGLAND FL (Keys) AUDREY (SW LA/N TX) NE U.S LA (Grand Isle) LA (New Orleans) TX (Galveston) CAMILLE (MS/LA)

Who’s to blame? Individuals who assumed risk, then didn’t listen and follow instructions Individuals who assumed risk, then didn’t listen and follow instructions New Orleans, for not having a real evacuation plan New Orleans, for not having a real evacuation plan The Corps of Engineers, for a century and more of false promises and wasted billions The Corps of Engineers, for a century and more of false promises and wasted billions FEMA et al., for not recognizing the scope of the impending disaster FEMA et al., for not recognizing the scope of the impending disaster Congress, for not funding adequate maintenance/upgrades of levee system Congress, for not funding adequate maintenance/upgrades of levee system

What do we do about it? Abandon New Orleans? Abandon New Orleans? Rebuild New Orleans only along the natural levees? Rebuild New Orleans only along the natural levees? Rebuild, but zone/plan undersea areas for only unoccupied ground floors? Rebuild, but zone/plan undersea areas for only unoccupied ground floors? Rebuild and raise the levees? Rebuild and raise the levees? Rebuild Rebuild

In summary…