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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 1 of 21

Note on the Influence of the Mississippi River Gulf Outlet on Hurricane Induced Storm

Surge in New Orleans and Vicinity

Joannes Westerink

Department of

University of

Civil Engineering and Geological Sciences

Notre Dame, Notre Dame IN 46556

Coastal and Hydraulics Laboratory, U.S. Army Engineering Research and Development Center

Bruce Ebersole

Vicksburg, MS 39180

Harley Winer

New Orleans District, U.S. Army Corps of

New Orleans, LA 70160

Engineers

February 21, 2006

Concerns have been raised regarding the role of the Mississippi River Gulf Outlet

(MGO) on storm surge propagation into metropolitan New Orleans and vicinity. This note
discusses hydrodynamic model simulations that evaluate the influence of the MRGO on flooding
during major hurricane events.

The physical system here is very complex, one comprised of a network of estuaries,

lakes, rivers, channels, and low lying wetlands, with topographic major relief defined by river
banks and an extensive system oflevees and raised roads. Water surface elevation response is
driven by storm surge, tides, and wind-waves. Both storm surge and tides are characterized as
forced very long wavelength inertial gravity waves, while wind-waves are gravity waves defined

by their short period. All three types of

waves propagate and experience various levels of local

forcing which can further build amplitudes. In metropolitan New Orleans and vicinity, the

amplitude of

the tides is small; the maximum tide range is on the order of one half

foot in Lake
Pontchartrain and two feet in Chandeleur Sound. The amplitude of a storm surge can be much
higher; for Hurricane Katrina, the peak storm surge along the MRGO adjacent to the S1. Bernard
ParishlChalmette hurricane protection levee was computed to be as much as 18 ft. This note
focuses on the relevant long period motion that dominates the circulation patterns in the area. In
particular, the impact of the MRGO on large scale catastrophic storm surge development and
propagation is examined.

The MRGO is a dredged channel that extends southeast to northwest from the Gulf of

Mexico to a point where it first merges with the GulfIntracoastal Waterway (GIWW), and then
continues westward until it intersects the Inner Harbor Navigation Canal (IHNC) as shown in
Figure i. The first 9 miles, the bar channel, are in the open Gulf. The next 23 miles of the
channel lie in the shallow open waters of Breton Sound. From there, the inland cut extends 14
miles to the northwest with open marsh on the northeast and a 4,000-ft wide dredged material
placement bank on the southwest side. At this point the channel cuts across the ridge of a relict

i

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 2 of 21

distributary of

hurricane protection levee atop a dredged material placement bank on the southwest side of

the Mississippi River, Bayou La Loutre. For nearly the next 24 miles, there is a
the
channel and Lake Borgne and open marsh lie to the northeast. A portion of the levee protecting
S1. Bernard ParishlChalmette and the portion of the hurricane protection levee along the south
side of Orleans East Parish, north of the GIWW, form the "funnel" that is often referenced. The
point where the MRGO and GIWW channels merge is just to the east of the Paris Road Bridge
(see Figure I). From this point, the merged GIWW/MGO channel continues west for about 6
miles to the point where it intersects the IHNC; this portion has hurricane protection levees on
both banks. The IHNC extends from Lake Pontchartrain, to the north, to the Mississippi River to
the south. The IHNC has levees or floodwalls along both banks. The IHNC Lock, which

the IHNC. The

connects the IHNC to the Mississippi River, is located at the southern limit of

or 450 ft, depending on location. Due to ship wave erosion, the surface width of

MRGO bar channel authorized depth is 38 ft; the authorized bottom width is 600 ft. The
remainder of the channel has an authorized depth of 36 ft and an authorized bottom width of 400
the channel has
increased since its construction at a rate of up to 15 ft per year. The additional eroded open water
typically has a depth of six feet or less. Therefore, even an additional 1000 feet of open water
adds no more than 6000 square feet of conveyance, about a 21 % increase over the authorized
channel (assuming the channel is 40 feet deep, has a 600 ft wide dredged bottom and a I to 3
side slope).

It is importnt to distinguish between two sections of the MRGO and the role each plays
in tide and storm surge propagation. One is the east-west oriented section that runs between the

IHNC and the confluence of

the GIWW/MGO near the Paris Road Bridge, labeled as the

GIWW/MGO in Figure I, and hereafter referred to as Reach 1. The other is the much longer
southeast-northwest section designated as the MRGO in Figure I, and hereafter referred to as the
Reach 2.

The critical section of

the MRGO is Reach i, the combined GIWW/MGO. It is through

this section of channel that Lake Pontchartrain and Lake Borgne are hydraulically connected to

one another via the IHNC. Reach I existed as the GIWW prior to the construction of

MRGO, although the maintained depth was lower. Because of

this connectivity, the local storm

the

surge and astronomical tide in the IHNC and in the section designated GIWW/MRGO is
influenced by the tide and storm surge in both Lake Pontchartrain and Lake Borgne. The two

Lakes are also connected to each other via the Rigolets and Chef

Menteur Pass; the IHNC is the

smallest of the three connections. The Reach I GIWW /MGO section of channel is very
importnt in determining the magnitude of storm surge that reaches the IHNC from Lake Borgne
and Breton Sound. Ifthe hydraulic connectivity between Lake Pontchartrain and Lake Borgne is

eliminated at a point within this section of channel, tide or surge to the west of

this point will

become primarily influenced by conditions at the IHNC entrance to Lake Pontchartrain; and tide
or storm surge to the east of this point wil become primarily influenced by conditions in Lake
Borgne.

Much concern seems to be focused on MRGOlReach 2 that runs from the GIWW/MRGO
confluence, just east of the Paris Road Bridge, to the southeast. Past work, McAnally and Berger
the
MRGO channel, along with the critical section, the GIWW/MGOlReach I, plays an important

(1997), Carillo et al. (2001), and Tate et al. (2002) for example, has shown that this section of

2

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 3 of 21

role in the propagation of

the astronomical tide wave and in the flux of more saline water from
Lake Borgne/Breton Sound into Lake Pontchartrain via the IHNC. The significant role of the

MRGO in the propagation of

the low-amplitude tide has been established.

Three previous studies have been performed to examine the influence of MRGOlReach 2

on flooding in New Orleans and vicinity. The first of

(1966), was performed for the U.S. Army Corps of

MV). The primary objective of

the study was to determine the effects of

these studies, Bretschneider and Collins
Engineers, New Orleans District (USACE-
the jlRGO channel,

and dredged material placement banks, and associated works, on the hurricane surge
environment of an area to the east of the Mississippi River from the southern end of the MRGO
to the IHNC. The study looked at Hurricane Betsy and six synthetic storms. Based on simplified
one-dimensional numerical computations and estimates of channel conveyance effects, the report
concluded that Betsy would have produced essentially the same surge elevations with or without
the MRGO.

The second study was also commissioned by the USACE-MVN and involved "closing"
the MRGOlReach 2 with a barrier placed across the MRGO extending out from state road 624

and the La Loutre Ridge (U.S. Army Corps of

Engineers, New Orleans District, 2003). That

closure was located just to the southeast of Shell Beach in Figure i. The study examined 9
synthetic storms with a track to the west of the Mississippi River running parallel to the MRGO
with input strengths varying from 65 to 124 knots and forward speeds ranging from 5 to 20
the 10 storms was

knots. In addition, Hurricane Betsy input winds were examined. Each of

simulated with and without the MRGO closure along the La Loutre Ridge. The study applied the

GIWW, IHNC, the Rigolets Inlet and Chef

S08 high resolution unstructured finite element grid with detailed refinement of

the MRGO,
Menteur Pass (Feyen et al. 2005, Westerink et al.
2006). Resolution and domain definition requirements have been verified for the S08 grid and
the resulting model has been validated (Blain et al. 1994, Blain et al. 1998, Westerink et al. 2000,
Feyen et al. 2002, Feyen et al. 2005, Westerink et al. 2006). The S08 grid applies a larger
approximation for the width of the MRGOlReach 2 channel, thus leading to conservative
estimates of the influence of the channeL. A two dimensional depth integrated version of the
ADCIRC model (Luettich et al. 1992, Luettich and Westerink 2004, Luettich and Westerink,
2005, Westerink et al. 2006), a finite element based shallow water equation code that is accurate,
stable and robust, was used to perform the computations.

Results from this study showed that for low-amplitude storm surges (peak surge having a
magnitude of 4 feet or less), the presence ofMRGOlReach 2 increased the storm surge by up to
the following amounts: 0.5 ft at Shell Beach and Bayou Dupre, and 0.3 ft at Paris Road Bridge
and the IHNC Lock. For nearly all situations that were examined (results for all ten storms at the

four locations shown in Figure i), the presence of

the MRGOlReach 2 either did not cause a

significant change or the increase was less than 0.3 ft. Ina few situations, notably a slow

moving weak storm, the presence of

the MRGOlReach 2 channel actually led to a very small

decrease in peak surge level at the four locations. For higher amplitude storm surges, peak
surges on the order of7 to 12 feet (which included Hurricane Betsy), changes induced by
MRGOlReach 2 were 0.3 ft or less for all situations. The MRGO did however considerably
enhance drainage from Lake Pontchartrain through the IHNCIGIWW out to Breton Sound

following passage of

the storms.

3

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 4 of 21

A follow up study was commissioned by the State of Louisiana, Departent of

Natural

Resources and implemented by URS Corporation (2006). This study applied the same
unstructured S08 grid but filled in the MRGOlReach 2 channel to surrounding
topographic/bathymetric levels. This study also applied the ADCIRC code and the results were

similar

to the USACE-MV study. Reach 2 of

the MRGO had a very limited impact on

increasing storm surge for large storms, including Hurricanes Betsy and Katrina. All changes

were less than 0.6 ft and most changes were less than 0.3 ft, in the vicinity of

New Orleans.

Results also indicated that the MRGO enhanced post storm drainage from portions of the system.

In general, the studies cited above reached consistent conclusions. The change in storm

surge induced by MRGOlReach 2 (computed as a percentage of the peak surge magnitude) is

greatest when the amplitude of

the storm surge is low, on the order of a few feet or less. In these

situations, changes induced by the MRGO are rather small, 0.5 ft or less, but this amount is as

much as 25% of

the peak surge amplitude. When the long wave amplitude is very low, the

surge is more limited to propagation via the channels. Once the surge amplitude increases to the
the MRGO plays a diminishing role

point where the wetlands become inundated, this section of

in influencing the amplitude of storm surge that reaches the vicinity of metropolitan New

Orleans. For storm surges of

the magnitude produced by Hurricanes Betsy and Katrina, which
overwhelmed the wetland system, the influence ofMRGOlReach 2 on storm surge propagation
is rather small. When the expansive wetland is inundated, the storm surge propagates primarily
through the water column over this much larger flooded area, and the channels become a much
smaller contributor to water conveyance.

The results of these studies can be readily understood by considering in more detail the

evolution of storm surge for critical hurricane tracks passing to the west of

the Mississippi River.
These storms blow wind across the region first from the norteast, then from the east, then from
the southeast and south and finally from the west. The sustained northeasterly and especially
easterly winds push water onto the wide and shallow Mississippi-Alabama Shelf into Breton and
Chandeleur Sounds, and Lake Borgne. These winds build surge up regionally on the shelf and in
particular against the Mississippi River and hurricane protection levees in Plaquemines Parish,
against the St. Bernard ParishlChalmette hurricane protection levee system and into the so called
funnel defined by the levees protecting St. Bernard ParishlChalmette and New Orleans East

along the confluence of

the GIWW/MRGO. As winds become southerly, the significant surge

that has built up along the Mississippi River levees in southern Plaquemines Parish starts to
propagate north as a constrained wave up the Mississippi River and as an unconstrained wave
through Breton Sound; both influenced by the strength and direction of the winds. Finally,
westerly winds blow surge away from these levees.

We note that the surge driven by the sustained northeasterly and easterly winds is not
water movement is from east to west across

influenced by the MRGO, since the direction of

Breton and Chandeleur Sounds and Lake Borgne. The brief southeasterly and southerly winds do
guide the substantial surge wave that has built up in Plaquemines Parish north across Breton
Sound. In the case of Hurricane Betsy, the surge propagated in a northerly direction along the
Mississippi River levees and was stopped by river levees at English Turn. In the case of
Hurricane Katrina, the surge propagated in a northeasterly direction perpendicular to the MRGO

4

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 5 of 21

towards Gulfport, Mississippi. In either case, the northerly movement of

water is not

significantly influenced by the MRGO since the size of

the surge is substantially larger than the
increased cross sectional area for flow, or conveyance, offered by the MRGO. Furthermore the

alignment of

the MRGO does not coincide with the direction of

propagation of

the massive surge

as it heads north and only briefly coincides with southeasterly winds which locally force flow.

We have simulated Hurricane Katrina both with the MRGOlReach 2 in place as well as

with the MRGOlReach 2 filled to surrounding bathymetric and topographic levels. The
hydrodynamic computations were performed with the TFO I ADCIRC model of Southern
Louisiana which is a refinement of the earlier S08 model with added details and resolution for

the coastal floodplains of

the north shore of

Lake Pontchartrain, Mississippi and Alabama

(Interagency Performance Evaluation Task Force, 2006). We applied identical wind and pressure
fields derived from a Planetary Boundary Layer (PBL) model to simulate the atmospheric

forcing functions during the Katrina event (Thompson and Cardone, 1996). A sequence of

hourly

snapshots of

water surface elevations with super-imposed winds (Figure 2) shows the evolution

of storm surge with the MRGO in place. More detailed elevation values are given in
corresponding labeled water elevation contour plots in Figure 3. Surge buildup starts with
easterly winds blowing water from east to west against the Mississippi River levees in
Plaquemines Parish as well against the hurricane protection levees of S1. Bernard
ParishlChalmette in addition to driving water into the funnel defined by the levees protecting St.
Bernard ParishlChalmette and New Orleans East. When winds become southerly, the massive
surge that has built up in Breton Sound propagates north. We note that the northeasterly
propagating storm surge has a crown of more than 16 ft above NGVD 29 extending out more

than 12 miles and water levels in the entire Mississippi-Alabama Shelf

NGVD 29.

exceed 10 ft above

The simulation without the MRGOlReach 2 results in very similar water levels in most of

the domain for the Katrina event. Differences in the maximum Katrina event water levels with
and without the MRGO in place are shown in Figures 4a and 4b. Notable differences with the

MRGO Reach 2 channel in place are as follows: there is a reduction of

at the entrance to the MRGO's inland cut; there is an increase of

up to 0.2 ft
0.3 to 0.4 ft in the marshes west

water level of

of the MRGO in the region delineated by Pointe a la Hache, Carlisle, Stella, Caernarvon and
Verret; a maximum increase of approximately 1.1 ft locally east of English Turn; in Lake Borgne
along the MRGO there is a 0.1 to 0.2 ft increase; there is a 0.1 to 0.2 ft decrease along the St.
Bernard ParishlChalmette protection levee; and finally there is a 0.1 to 0.2 ft increase in a portion
of the GIWW/MGOlReach 1. In all other regions, including in the IHNC, differences are less
than 0.1 ft. In addition, the New Orleans and vicinity protection system is not impacted more
than 0.2 ft. These results coincide with those from the earlier studies. We note that the small
increases in surge due to the presence of MRGOlReach 2 can be traced to the alignent of the
local southeasterly winds that briefly occur later in the storm and that do in fact drive more water
up the MRGOlReach 2. These waters then feed into the northward-propagating surge wave and
spread laterally relative to the propagation direction. However due to fact that the alignment
between the wind and the MRGOlReach 2 is brief and in light of the shelf-wide high water levels
at this stage of the storm, the impact on channel conveyance is smalL. The largest difference and
its associated pattern seen at English Turn is related to this mechanism as well as small
differences in the northward propagating waves' phasing properties coupled with the winds

5

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 6 of 21

turning at this point as the eye of the storm moves across this area. The small decreases in
maximum water elevations occur due to a small reduction in the local resistance to water being
pushed by local winds in a northwesterly direction at the entrance to the MRGO/Reach 2 inland
cut and due to increased water depths reducing local set-up against the S1. Bernard Parish!
Chalmette protection levee (local wind driven set-up is inversely proportional to the depth ofthe

water). .

The reasons for the very limited influence of

the MRGOlReach 2 in the vicinity of

New

Orleans for strong storm events are clear. First, the MRGO does not influence the importnt
preliminary east-west movement of water that drives the significant build up of surge in the

early parts of

the storm. Second, the northerly propagation of surge during the

later stages ofthe
storm are only minimally influenced by the MRGO because the increased hydraulic conveyance
associated with the channel is very limited for large storms due to the large surge magnitude and
especially due to the very large lateral extent of the high waters on the Mississippi-Alabama
this surge

that build up early on from the east. In addition, the propagation direction of

shelf

wave does not typically align with the MRGO and furthermore the southeasterly winds which
align with the MRGO occur only very briefly.

The fact that all studies show a larger proportional influence of the presence of the

MRGOlReach 2 for low intensity (low peak surge magnitude) events is related to the fact that the
proportional increase in conveyance due to Reach 2 is greater when the surge is small and the
water levels in Breton Sound and Lake Borgne are generally low. This also explains why we see
a more rapid drop in post-storm Lake Pontchartain levels for large-scale events with the MRGO
in place. Waters typically withdraw relatively rapidly from Breton Sound and Lake Borgne due
to the direct connection to open waters. The total combined conveyance of the Rigolets, Chef
Menteur Pass and the IHC/GIWW/MGO system is increased with the MRGO in place under
the lower post-storm levels on the Mississippi-Alabama shelf.

While the simulations clearly show that the Reach 2 of the MRGO does not significantly

influence the development of surge in the region for large storm events, the presence of the
critical Reach i combined GIWW/MGO and IHNC connection between Lake Borgne and Lake
Pontchartrain as well as the funnel defined by the hurricane protection levees along the banks of
the MRGO and GIWW locally collect and focus surge in the region, influencing all
hydraulically-connected regions as well as New Orleans proper. The degree offocusing by the
levees which form the funnel is a function of the wind speed and direction. Strong winds from
the east tend to maximize the local funneling effect.

6

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 7 of 21

References

Blain, C.A., U. Westerink and R.A. Luettich, 1994: The Influence of Domain Size on the
Response Characteristics of a Hurricane Storm Surge ModeL. Journal of Geophysical
Research - Oceans, 99, C9, 18467-18479.

Blain, c.A., U. Westerink and R.A. Luettich, 1998: Grid Convergence Studies for the Prediction
of Hurricane Storm Surge. International Journal for Numerical Methods in Fluids, 26, 369-
401.

Bretschneider, C. L., and J.r. Collins, 1966: Storm Surge Effects of

the Mississippi River-Gulf

Outlet, Study A. NESCO Report SN-326-A, National Engineering Science Company,
Pasadena, CA.

Carillo, A. R., R.C. Berger, M.S. Sarruff, and 8.J. Thibodeaux, 2001: Salinity Changes in
Pontchartrain Basin Estuary, Louisiana, Resulting from Mississippi River-Gulf Outlet

Partial Closure Plans. ERDC/CHL TR-OI-04, U.S. Ary Corps of

Research and Development Center, Vicksburg, MS.

Engineers, Engineer

Feyen, J.C., J.H. Atkinson and J.1. Westerink, 2002: GWCE-Based Shallow Water Equation

Simulations of

the Lake Pontchartrain - Lake Borgne Tidal System. Computational Methods
in Water Resources XIV, S.M. Hassanizadeh et al. Eds., Volume 2, Developments in Water
Science, 47, Elsevier, Amsterdam, 1581-1588.

Feyen, J.C., U. Westerink, R.A. Luettich, J.H. Atkinson, C.N. Dawson, M.D. Powell, J.P.

Dunion, H.1. Roberts, E. J. Kubatko, H. Pourtheri, 2005: A New Generation Hurricane
Storm Surge Model for Southem Louisiana. Bulletin of the American Meteorological
Society, In Review.

Interagency Performance Evaluation Task Force, 2006: Performance Evaluation Plan and
Interim Status, Report I of a Series; Performance Evaluation of the New Orleans and
Southeast Louisiana Hurricane Protection System. Report MMTF 00038-06, U.S. Army

Corps of

Engineers, Washington D.C.

Luettich, R.A., J.J. Westerink, and N.W. Scheffner, 1992: ADCIRC: An Advanced Three-
Dimensional Circulation Model for Shelves, Coasts and Estuaries, Report I: Theory and
Methodology of ADCIRC-2DDI and ADCIRC-3DL. Technical Report DRP-92-6,

Departent of

the Army, U.S. Ary Corps of

Engineers, Washington D.C.

Luettich, R.A. and U. Westerink, 2004: Formulation and Numerical Implementation ofthe

2D/3D ADCIRC Finite Element Model Version 44.XX.
htt://ww.marine.unc.edu/C CATS/adcirc/adcirc theorv 2004 12 08.pdf

Luettich, R.A. and U. Westerink, 2005: ADCIRC: A Parallel Advanced Circulation Model for

Oceanic, Coastal and Estuarine Waters; Users Manual for Version 45.08.
htt://ww.marine.unc.edu/C CATS/adcirc/documentlADCIRC title page.html

7

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 8 of 21

McAnally, W. H., and R.C. Berger, 1997: Salinity Changes in Pontchartrain Basin Estuary
Resulting from Bonnet Carre Freshwater Diversion. Technical Report CHL-97-2, U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.

Tate, J. N., A.R. Carilo, R.C. Berger, and B.1. Thibodeaux, 2002: Salinity Changes in

Pontchartain Estuary, Louisiana, Resulting from Mississippi River-Gulf Outlet Partial

Closure Plans and Width Reduction. ERDCICHL TR-02-12, U.S. Army Corps of

Engineer Research and Development Center, Vicksburg, MS.

Engineers,

Thompson, E.F., and V.1. Cardone, 1996: Practical Modeling of

Hurricane Surface Wind Fields.

Journal of Waterway, Port, and Coastal Engineering., 122,4,195-205.

U.S. Army Corps of

Engineers, New Orleans District, 2003: Numerical Modeling of

Surge Effect ofMRGO Closure. New Orleans, LA.

URS Corporation, 2006: The Direct Impact of

the Mississippi River Gulf

Storm Surge. Performed under contract 2503-05-39, Prepared for State of

Department of

Natural Resources, Baton Rouge, LA.

Storm

Outlet on Hurricane

Louisiana

Westerink, U., R.A. Luettich, H. Pourtheri, 2000: Preliminary Sensitivity Studies of Tidal
Response in the Lake Ponchartain-Lake Borgne System. Contractors report prepared for the

U.S. Army Corps of

Engineers, New Orleans District, New Orleans, LA.

Westerink, J.J., R.A. Luettich, J.C. Feyen, J.H. Atkinson, C. Dawson, M.D. Powell, J.P. Dunion,
H.1. Roberts, E. J. Kubatko, H. Pourtheri, 2006: A Basin to Channel Scale Unstructured
Grid Hurricane Storm Surge Model for Southern Louisiana. Monthly Weather Review, To
be submitted.

8

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 9 of 21

Figure la. Satellte image of Southeastern Louisiana.

Figure I b. Satellite image of metropolita New Orleans and vicinity.

9

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 10 of 21

-::---iai--
....".
...
,..
'"..
..
::.-..--...aI-

.....-

Figure 2a. Water surface elevation with respect to the NGVD29 (ft) with boundar layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29, 2005 at 0700UTC.

-----..:~_..
~......,..
.......
..
:::..---.-'''.-

Figure 2b. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29, 2005 at 1000UTC.

10

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 11 of 21

..,

-::---..,ii-
.,.,."
'".,"..
::'.,--...-

Figure 2c. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29, 2005 at Ii OOUTC.

-::---in,....
.'."".,..
..,......
::'~----,"'..-

Figure 2d. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 1200UTC.

II

.-

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 12 of 21

-::---in:ii--
.'.,".,"
'"......
::'..--.~-

.....-

Figure 2e. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 1300UTC.

Figure 2f. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 1400UTC.

12

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 13 of 21

Figure 2g. Water surface elevation with respect to the NGVD 29 (ft) with boundar layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 1500UTC.

..,

-..---IU'--
_..'.,u'"
..,"..i:,
.,--.._-

,"....-

Figure 2h. Water surface elevation with respect to the NGVD 29 (ft) with boundar layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 1600UTC.

13

,

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 14 of 21

-----in,--
~...'."
~,~--.._-

'","
..,..
..

Figure 2i. Water surface elevation with respect to the NGVD 29 (ft) with boundary layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at l700UTC.

"":t---q,--
.,..".
..,....
..

...

Figure 2j. Water surface elevation with respect to the NGVD 29 (ft) with boundar layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29,2005 at 2000UTC.

14

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 15 of 21

-=--_-..,.,iaø
'".,."

'"
..,

'""..'-...,----

Figure 2k. Water surface elevation with respect to the NGVD 29 (ft) with boundar layer adjusted
wind velocity vectors (knots) during Hurricane Katrina on August 29, 2005 at 2300UTC.

-~---..,_ø
...''"'"
,,,".."...,

..,

~

Figure 3a. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29,2005 at 0700UTC.

15

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Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 16 of 21

-----ia,-""
~...,",
..,....
....~

...
..,

Figure 3b. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29,2005 at 1000UTC.

-::---II'''--
'".,",
..,...."...'

'"
..,

Figure 3c. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29,2005 at IIOOUTC.

16

~

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 17 of 21

------..,-""

-...'."..,........~...,

. Figure 3d. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during

Hurricane Katrina on August 29, 2005 at 1200UTC.

"":o-_---:io,,,,,
...,
'"...
,......"
~".,

Figure 3e. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29, 2005 at l300UTC.

17

-

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 18 of 21

-----ia,--
~...,.",..
"'....uu.,

..,

Figure 3f. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane KatrIna on August 29, 2005 at 1400UTC.

-;:---iA:_-
...,
'"..,
...
,,,..
..u....

Figure 3g. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29, 2005 at 1500UTC.

18

-

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 19 of 21

-.:---""'--
...,."
..,....,..""".,

Figure 3h. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29,2005 at 1600UTC.

-:0---II:--
.'.,..'"
'"...."..".,

Figure 3i. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29, 2005 at 1700UTC.

19

~

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 20 of 21

-----....,--

-...,.",..,"......

~..~

Figure 3j. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29, 2005 at 2000UTC.

-----ii:"-""
_..'.,
'"'"
.....""
~".,

Figure 3k. Water surface elevation with respect to the NGVD 29 (ft) with labeled contours during
Hurricane Katrina on August 29, 2005 at 2300UTC.

20

-

Case 1:05-cv-01119-SGB Document 27-4 Filed 10/04/2006 Page 21 of 21

""--ut_""'8--

'"

..............

-~

: .~
--¿-, ."¡'!;
r~ 'Po
-:"'.'

-I ~

8

"/./

Figure 4a. Maximum Hurricane Katrina event differences in ft, for simulations with and without the
MRGO in place. Positive differences indicate increased elevations with the MRGO in place while
negative differences indicate decreased water levels with the MRGO in place.

-.

--./

--_-~ ~1.1 ..
,..................,..

4'......

~-. ~~.: \ '

._,~~ )
) ~l- I.,

Figure 4b. Maximum Hurricane Katrina event differences in ft in metropolitan New Orleans and
vicinity, for simulations with and without the MRGO in place. Positive differences indicate increased
elevations with the MRGO in place while negative differences indicate decreased water levels with
the MRGO in place.

21

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