Part 2Part 2

OVERTOPPING OF OVERTOPPING OF FLOOD FLOOD

CONTROL CONTROL STRUCTURES STRUCTURES

Locations of breaks in the flood control Locations of breaks in the flood control system surrounding New Orleans caused by system surrounding New Orleans caused by KatrinaKatrina

Flooded areas Flooded areas shown in pinkshown in pink

Overtopping:Overtopping: Earthen levee being overtopped at the Earthen levee being overtopped at the Entergy Power Plant, Inner Harbor Navigation Entergy Power Plant, Inner Harbor Navigation Channel. This began around 6 AM on August 29Channel. This began around 6 AM on August 29thth. 9 ft . 9 ft storm surge with crest heights up to 17 ftstorm surge with crest heights up to 17 ft

Good performance:Good performance: some portions of the some portions of the Mississippi River Gulf Outlet (MRGO) ChannelMississippi River Gulf Outlet (MRGO) Channelsurvived waves as high as 17 feet, caused by a 9 survived waves as high as 17 feet, caused by a 9 foot storm surge off Lake foot storm surge off Lake BorgneBorgne (to the right) (to the right)

Survivable levee:Survivable levee: The storm surge pushed houses up The storm surge pushed houses up on top of some levees, leaving them scattered about on top of some levees, leaving them scattered about

Poor performancePoor performance: Skeleton of : Skeleton of steel steel sheetpilesheetpilecutoff wallscutoff walls is all that remains of the is all that remains of the MRGO MRGO leveelevee between Bayou between Bayou BienvenueBienvenue and Bayou and Bayou DupreeDupree

Poor performance:Poor performance: MRGO leveeMRGO levee completely washed completely washed away about two miles southeast of Bayou Dupree.away about two miles southeast of Bayou Dupree.

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0.1 1.0 10.0 100.0Velocity (m/s)S1-B1-(0-2ft)-TW S1-B1-(2-4ft)-SW S2-B1-(0-2ft)-TWS2-B1-(2-4ft)-SW S3-B1-(2-4ft)-SW S3-B2-(0-2ft)-SWS3-B3-(0-1ft)-SW S4-(0-0.5ft)-LC-SW S4-(0-0.5ft)-HC-SWS5-(0-0.5ft)-LT-SW S6-(0-0.5ft)-LC-SW S7-B1-(0-2ft)-TWS7-B1-(2-4ft)-SW S8-B1-(0-2ft)-TW S8-B1-(2-4ft)-L1-SWS8-B1-(2-4ft)-L2-SW S11-(0-0.5ft)-LC-TW S11-(0-0.5ft)-HC-TWS12-B1-(0-2ft)-TW S12-B1-(2-4ft)-SW S15-Canal Side-(0-0.5ft)-LC-SWS15-CanalSide-(0-0.5ft)-HC-SW S15-Levee Crown-(0-0.5ft)-LT-SW S15-Levee Crown-(0.5-1.0ft)-LT-SW

Very HighErodibility

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HighErodibility

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The key to levees surviving overtopping is the clay The key to levees surviving overtopping is the clay content. Much of the dredged material consisted of content. Much of the dredged material consisted of organic silt, which does not have substantive cohesionorganic silt, which does not have substantive cohesion

Many of the problems along the MRGO Channel occurred at Many of the problems along the MRGO Channel occurred at structural transitions, between dissimilar elements, such as structural transitions, between dissimilar elements, such as earthen levees against concrete flood walls, shown here.earthen levees against concrete flood walls, shown here.

Some sections survived:Some sections survived: Evidence of Evidence of sustained overtopping of concrete flood wall sustained overtopping of concrete flood wall along the IHNC in the Lower Ninth Ward.along the IHNC in the Lower Ninth Ward.

ING 4727 bargeING 4727 barge

Overtopping scour holes along landside of flood wall on west Overtopping scour holes along landside of flood wall on west side of the IHNC. Note broken wall in background. A splash pad side of the IHNC. Note broken wall in background. A splash pad on inboard side could have prevented this undercutting for less on inboard side could have prevented this undercutting for less than 0.5% of the flood wall cost, making the structure than 0.5% of the flood wall cost, making the structure ““Class 3 Class 3 survivable.survivable.””

Structures must beStructures must beClass 3 survivableClass 3 survivable

It is impossible to accurately predict actual flood surge heights, because of a number of unknown factorsEngineers have to select a flood height commensurate with risk-consequence assessments and probabalistic analyses.Consequences in a densely populated urban areas never a factor previouslyFlood control infrastructure, such as levees and flood walls, must be designed to withstand sustained overtopping.

THE LESSONS OF KATRINA – WHAT WE ALL �SHOULD KNOWPart 1Hurricane Katrina Storm SurgeKatrina makes LandfallPart 2Structures must be� Class 3 survivablePart 317th Street Drainage Canal breachLondon Avenue (North) breachLondon Avenue (South) breachPart 4POLICY ISSUES - 1POLICY ISSUES -2Part 5�EMERGENCY PREPAREDNESS ISSUES:�You have to think like the militaryYou have to think like the militaryDISASTER PLANNING ESSENTIAL for RECOVERYEVACUATION AND LIFE SAFETYEMERGENCY RESPONSEREFUGEE SUPPORTENVIRONMENTAL RESPONSEPREPAREDNESS ISSUESIdentifying Critical Facilities and Components for Disaster ResponseImportance of ExercisesECONOMIC IMPACTSPart 6�CRITICAL ROLE OF THE MEDIA�IN DISASTER EXERCISES, PUBLIC EDUCATION, AND THE REAL THING MEDIA COVERAGE OF KATRINA-1MEDIA COVERAGE OF KATRINA-2MEDIA IMPACTS -1MEDIA IMPACTS -2The Great Mississippi Flood of 1927Operation Overlord9/11: An example of good media managementMEDIA REPORTS TEND TO INCLUDE “MAYBE” STATEMENTSHeadlines on holdLike it or not, we have to court the mediaAbout the Presenter