USACE GEEZER BRIEF 2001

1
Hurricane Katrina Lessons Learned A Perspective
from the Interagency Performance Evaluation
Taskforce (IPET)
Jerry W. Webb, P.E. D.WRE HQ US Army Corps of
Engineers Principal Hydrologic Hydraulic
Engineer
NOAA/NWS National Hydrologic Program Managers
Conference Kansas City, MO 10 July 2007
2
Hurricane Katrina

• One of Americas largest natural disasters
• Category 5 strength less than 12 hours before
  landfall
• 127 MPH wind at Louisiana landfall
• Peak water level of 28 feet along Mississippi
  coast, 21 feet in Louisiana. (Highest storm surge
  ever measured on U.S. coast)
• Highest significant measured wave in Gulf of
  Mexico or Atlantic Ocean

3
Was this a wake up call?
What did we learn? How do we apply it?
4
Flooding 2005
5
Flooding 2005
6
Surge
7
Comparison of Design and Katrina Surge Levels
Surge D 11 ft K 10 ft
Surge D 13 ft K 17 ft
Surge D 12 ft K 17 ft
Surge D 14 ft K 20 ft
Surge D 13 ft K 17 ft
8
Comparison of Design and Katrina Waves
Height/Period D 7.8 ft / 7.3 sec K 8.7 ft / 6.7
sec ft
Height/Period D 4.9 ft / 5.5 sec K 5.2 ft /16.3
sec
Height/Period D 7 ft / 6.4 sec K 5.2 ft / 16.3 sec
Height/Period D 5.4 ft / 5.6 sec K 9.4 ft / 13.5
sec
Height/Period D 5.2 ft / 4.7 sec K 7.6 ft / 14.9
sec
9
Interagency Performance Evaluation Task Force
(IPET)
Evaluation of New Orleans and Southeast Louisiana
Hurricane Protection System
25 Universities 23 Private Firms 8 Government
Agencies
Over 150 experts from 58 organizations Peer
reviewed by ASCE and NRC
10
Chief of Engineers Charge to IPET
to provide credible and objective scientific
and engineering answers to fundamental questions
about the performance of the hurricane protection
and flood damage reduction system in the New
Orleans metropolitan area.

Chief of Engineers Lt. General Carl
Strock Commander, U.S. Army Corps of Engineers

• The Flood Protection System What were the design
  criteria for the pre-Katrina hurricane protection
  system, and did the design, as-built
  construction, and maintained condition meet these
  criteria?
• The Storm What were the storm surges and waves
  used as the basis of design, and how do these
  compare to the storm surges and waves generated
  by Hurricane Katrina?
• The Performance How did the floodwalls, levees,
  pumping stations, and drainage canals,
  individually and acting as an integrated system,
  perform in response to Hurricane Katrina, and
  why?
• The Consequences What have been the
  societal-related consequences of the
  Katrina-related damage?
• The Risk Following the immediate repairs, what
  will be the quantifiable risk to New Orleans and
  vicinity from future hurricanes and tropical
  storms?

11
IPET Report
https//ipet.wes.army.mil
Volume 1 Executive Summary and Overview Volume
2 Geodetic Vertical and Water Level
Datum Volume 3 The Hurricane Protection System
- Jul 07 Volume 4 The Storm Volume 5 Levee
and Floodwall Performance - Jul 07 Volume 6
Interior Drainage and Pumping Performance Volume
7 Consequences Volume 8 Risk and Reliability
Draft Jun 07 Volume 9 General Appendices
12
Lake Pontchartrain
B
A
New Orleans
River
FLOODWALL ALONG
Mississippi
30
HURRICANE
MISSISSIPPI RIVER
PROTECTION LEVEE
FLOODWALL
A
23 FT
20
20
B
18 FT PROJECT FLOWLINE
17.5 FT
AVG ANNUAL HIGHWATER 14 FT
SPH DESIGN ELEV 11.5 FT
10
10
NORMAL LAKE 1.0 FT LEVEL
GENTILLY
ELEVATIONS IN FEET NGVD
RIDGE
0
0
UNO
RIVER BANK
-10
-10
LAKE
CATHEDRAL
PONTCHARTRAIN
SHORE
-20
DERBIGNY AT I-10
CANAL ST AT RIVER
-20
ST. ANTHONY AT
GENTILLY BLVD
ESPLANADE AT
WAINRIGHT DR
WAINRIGHT DR
AT L.C. SIMON
DILLARD UNIV
UNO SIDE OF
WILDAIR DR
ST. CLAUDE
ST. LOUIS
AT ALLEN
CAMPUS
MISSISSIPPI
13
New Orleans AreaHurricane Protection System
Orleans East Bank
Lake Pontchartrain
17th Street Canal
Orleans Ave. Canal
London Ave. Canal
New Orleans East
IHNC
GIWW
Lake Borgne
St. Bernard
Plaquemines
MRGO
Mississippi River
350 Miles Levee/ Floodwall 71 Pumping
Stations (Fed Non-Fed) 4 Gated Outlets
14
Conclusions The System Did Not Perform as a
System

• Datum disconnects (including subsidence)
• Design based on outdated criteria (SPH)
• Structures and design not updated for change in
  hazard and at risk development
• Construction never completed
• Structures not designed for events exceeding
  design (overtopping conditions)

15
Pre-Katrina vs Authorized Elevations
16
Key FindingsTransitionswere weak spots in the
system often elevation differencesLeveesperfor
med well until overtoppingbreaching occurred
from water cascading down protected sidewere
most vulnerable to breaching if hydraulic
fillFloodwalls at four sites experienced
failure before design water levels failures
initiated by deflection of wallunderlying clay
was failure plane for 17th and Lower 9thporous
sand at London Ave allowed piping and
erosionexperienced failure from overtopping
causing erosion behind wall
Performance
17
Transition Failure
18
Levee Overtopping and Scour
19
Floodwall Overtopping and Scour
20
Velocities and Wave Loadings on Levees

• Back side velocities 10-15 ft/sec
• Front side velocities 3 - 5 ft/sec
• Back-side scour predominated
• Wave forces 20 to 30 of forces on levees and
  floodwalls
• Peak significant wave heights in GIWW/MRGO
  channel 4 ft
• Peak wave heights 2 to 3 ft in IHNC

21
Dominant Failure Modes
Foundation Failure before Overtopping
Floodwall Overtopping and Scour
Levee Overtopping and Scour
(Highly correlated to Levee Materials)
22
Floodwall Foundation Failures
23
Conclusions Performance was Less than Design
Intent

• Levee breaching (46) due to overtopping and
  backside erosion
• Design not robust for overtopping conditions
• Overtopping velocities on backside 3xs wave
  velocities on front side
• Floodwall failure (4) due to geotechnical/foundati
  on failure
• Deflection of wall
• Levee split in two
• Seepage and increase hydrostatic pressure

Four I-wall foundation failures, with loadings
less than design.
24
Consequences

• 2/3rds volume of water in Orleans, east bank, and
  St Bernard came through breaches
• Rest is overtopping, seepage, and rainfall
• Economic losses would have been half if
  structures had held
• 700 fatalities (primarily elderly and poor)
• Mapped impacts to support Risk assessment
• Indirect Consequences?

25
Drainage and Pumping Performance
Katrina
No Breaching
26
Consequences
Key Findings Fatalities Included over 727 in
New Orleans over 70 percent were over age of 60
Property losses (private property) were over
20 B public property losses were an additional
7-8 B 78 residential (2 industrial) Environ
mental Greatest loss was 118 square miles of
marsh Water quality was not a significant
issue Social / Cultural Only 8 of 73
neighborhoods were not flooded, 34 were totally
inundated. loss of social fabric of community
may be largest long term loss
27
USACEs Actions for Change

• Comprehensive systems approach
• Risk-informed decision making
• Communication of risk to the public
• Professional and technical expertise

28
Comprehensive Systems Planning

• Multi-component, multi-dimensional problems
• Risk-based formulation and evaluation of
  alternatives
• Expanded stakeholder involvement

• Being applied to Louisiana Coastal Protection
  Restoration (LaCPR) and Mississippi Coastal
  Improvement Program (MsCIP)

29
Risk Communication
Today, you have a 1 chance (1 in 100) every year
in Gentilly of experiencing flooding this deep
from Hurricanes

• Convey to the public that risk still exists, no
  matter what protective measures are in place
• An informed public is empowered to take
  responsibility for their own safety

6-8 Less Flooding
Feet of Flooding
Gentilly Blvd
30
Hurricane Risk Communication

• Storm Surge Potential (in meters)

8 m
Camille
7 m
Katrina
6 m
Hurricane Intensity (milibars)(cent. press.
Defecit)
5 m
Betsy
Rita
4 m
3 m
Hurricane Size (Radius in nautical miles)
2 m
31
Risk Based System Wide Assessment
SYSTEM RELIABILITY
HAZARD
CONSEQUENCES
Probability based hurricane hydrographs (surge
and wave levels) at 138 locations for three
system geometries resulting from 152 storms (25
to 5000 yr)
Probability based expected performance of 134
reaches and 350 features for each storm
surge/wave level resulting in estimated flood
elevations by sub-basin
Probability based expected losses (fatalities
with no evacuation and property) by sub-basin
for the spectrum of storms
RISK
Annualized losses by sub-basin for Pre-Katrina
and Current HPS
32
Hurricane Hazard ResultsUsing JPM-OS
20,976 hydrographs for each of 3 scenarios
(pre-Katrina, current, hypothetical 100yr, and
eventually future level of protection)
152 storm hydrographs at each of 138 locations
for 3 HPS conditions Storms represent 25 to 5000
plus year events
33
Reliability AnalysisHow will each structure (by
reach) perform?
Global and Local Stability
Fragility Curves
Erodibility Index Factor
1
3.0 ft
2.0 ft
Overtopping Erosion
Erosion
Probability of Failure
1.0 ft
Overflow
0.5 ft
Minor
Moderate
Global Stability
Design
Severe
0
Water Elevation (NAVD88 (2004.65))
134 Reaches and 350 Features for 3 HPS Geometries
34
Loss Relationships by Sub-Basin
Property and Life loss relations developed for 34
sub-basins
35
Example Reliability Curves
36
Subsidence
Regional Long Term
Current Rates
37
Relative Annual Occurrence of Large Storms
38
The Hazard is Dynamic and Appears Cyclic
Plot of estimated cumulative kinetic energy for
all storms 1941-2005.
39
Flood Inundation Probabilities
40
Pre-K
Before Katrina, you had a 1 chance every year
of flooding this deep from Hurricanes
41
Today, you have a 1 chance every year of
flooding this deep from Hurricanes
Current
42
Before Katrina, you had a 1 chance every year
of flooding this deep from Hurricanes

• Lakeview

John F. Kennedy High School
Edward Hynes Elementary School
43
Today, you have a 1 chance every year of
flooding this deep from Hurricanes

• The current
• completed work has
• reduced the likely
• depth of flooding in
• Lakeview by over
• 5 feet.

John F. Kennedy High School
Edward Hynes Elementary School
44
Reduction of Consequences

Property Losses Decreased by
Estimated Fatalities Decreased by
Average Depth of Flood Water Decreased by
32
70
5.5 ft
Lakeview
This estimate assumes NO Evacuation
45
Always Remember Nature Bats Last!
Change Life Cycle Systems Policy and Practice
RISK