storm protection & coastal restoration: moving in to the 21 st century
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Storm Protection & Coastal Restoration: Moving in to the 21 st Century. Denise J. Reed University of New Orleans. Restore or Retreat March 2009. Master Plan Objectives. Objective #1: Reduce economic losses from storm based flooding - PowerPoint PPT PresentationTRANSCRIPT
Storm Protection & Coastal Restoration: Moving in to the 21st Century
Denise J. ReedUniversity of New Orleans Restore or Retreat
March 2009
Master Plan Objectives• Objective #1: Reduce economic losses from storm
based flooding• Objective #2: Promote a sustainable coastal
ecosystem by harnessing the processes of the natural system
• Objective #3: Provide habitats suitable to support an array of commercial and recreational activities coastwide
• Objective #4: Sustain the unique heritage of coastal Louisiana
Main Points• It’s an ever changing system• What does it take to achieve
sustainability?– Maximize the use of our resources– Capitalize on natural processes
• What do we need to do now?– Establish leadership and engage national
stakeholders and technical experts
LaroseLaroseGIWWGIWW
CocodrieCocodrieB
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B. T
erre
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B. G
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llou
B. G
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B. L
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GIWWGIWWPresquilePresquile
BoudreauxBoudreaux
B. P
etit
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B. P
etit
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Lafourche Parish
Lafourche Parish
Terrebonne Parish
Terrebonne Parish
NNBourgBourg
AshlandAshland 56
ChauvinChauvin
55
57
315
DulacDulac
Morganza to the Gulf of Mexico
Project
Morganza to the Gulf of Mexico
Project
REACH AREACH AREACH AREACH A
REACH BREACH BREACH BREACH B
Houma Navigation Canal LockHouma Navigation Canal Lock
Sector GatesSector Gates
Work in Kind (WIK) LeveesWork in Kind (WIK) Levees
Federal Levee AlignmentFederal Levee Alignment
MontegutMontegut
REACH EREACH EREACH EREACH E
REACH FREACH FREACH FREACH F
REACH HREACH HREACH HREACH H
REACH GREACH GREACH GREACH G
REACH IREACH IREACH IREACH I
REACH JREACH JREACH JREACH J
REACH KREACH KREACH KREACH K
REACH LREACH LREACH LREACH L
REACH J-1REACH J-1REACH J-1REACH J-1
HoumaHouma
MINORS CANAL
REACH A
REACH B
REACH E
REACH F
REACH H-1
REACH H
REACH I
REACH J REACH K
REACH L
REACH G
Wetlands Behind Levees = Opportunities?
More tidal exchange = more opportunity for sediment input
Existing levees
Existinglevees
Roads
MORGANZA-TO-THE-GULF TECHNICAL PANEL REVIEW
• Robert Twilley (Chair), Ph.D.• Mead Allison, Ph.D.• Louis Capozzoli, Sc.D., P.E. Retired• Shirley Laska, Ph.D.• Larry McKee, P.E.• Ehab Meselhe, Ph.D., P.E.• Denise Reed, Ph.D.• Tim Ryan, Ph.D.
http://www.lacpra.org/assets/docs/MtG%20Final%20Report_5%20Dec%2008.pdf
Basic Assessment
•Continue work on levees, floodgates and environmental structures on the current authorized levee alignment with the goal of providing a minimum system-level of protection (e.g., equivalent to that currently provided by the J1 reach) to the planning area (Phase 1 construction).
•Continue work on the HNC lock-floodgate structure given its vital role in the protection system and its potential to be used to benefit the ecosystem.
Basic Assessment
•Integrate proactive wetland restoration approaches (funded under other authorities) into the ongoing design and operation of the Morganza project.
•Routinely (e.g., every 5 years), revisit the project to reassess risk to communities and the economy, evaluate ecological impacts and benefits, and revise future construction and operation plans and schedules as appropriate.
Planning for Flood Risk Reduction
•Initiate a comprehensive, community-based planning process to identify the elements that need to be protected for the Terrebonne communities to thrive.
•Increase efforts to inform the business community and the general public of the level of protection and risk reduction provided.
•Implement a comprehensive flood management approach for the area that leverages existing programs for non-structural flood risk reduction, provides incentives to businesses and the general public, and provides for the safe location of future development.
USACE Slide courtesy of Pete Rabbon
Planning for Flood Risk Reduction
• Develop conservation easements, land-use plans and zoning ordinances to protect existing wetlands in the planning area from loss to development.
• Initiate a public education program to communicate scientifically based assessments economic benefits of improved construction standards on residual risk in the context of future storm frequency, sea level rise and subsidence, oil and gas activities.
Improved Tools and Analyses for Assessment of Integrated Risk Reduction Outcomes
•Continue to develop a system-wide model and use it, as well as conceptual models and monitoring, to design and operate environmental structures within the levee system; and convene an independent expert panel to guide this adaptive management process.
•Hold a workshop and/or convene a panel to consider the effects of flooding and salinity changes on wetland plant communities and soil development processes to inform evaluation of project effects on wetlands.
•Apply planning tools that allow integrated, spatially explicit assessments of structural and non-structural measures in risk reduction and that consider a range of possible future economic, social and environment scenarios.
Sustainability?Master Plan Planning Objective 2• Promote a sustainable coastal ecosystem by
harnessing the processes of the natural system.– providing for daily, seasonal, and episodic fluctuations in
water levels and salinities, and/or reestablishing natural pathways of sediment movement and nutrient uptake.
– Appreciation of the dynamic nature of the coastal system must be integral to the planning and selection of preferred alternatives
– route riverine waters through estuarine basins
The Past
Open bay Open bay
Min
imum
Ma
xim
um Growth Decay
DEL
TA
A
LO
BE
SI
Z
ED
LN
(A
RE
A)
Time
Subaqueous leveesMudflats
Freshwater marshBrackish marsh
Saline marshSwamp
LakesOyster reefs Oyster reefs
Marginal beachesBarrier islands
UBMERGED GROWTHS APID AERIAL GROWTHR ETERIORATIOND
BIOLOGICAL
DIV
ER
SIT
Y
Plaquemine
Lafourche
St. Bernard
Teche
Maringouin
Current stage of specific delta lobes
Na
tura
l env
iron
me
nts
Continuing Current Management
Achieving Sustainability
Coast 2050 Coast 2050 Coast 2050 Coast 2050
Is it achievable?
• There’s not as much sediment in the river as there used to be……
• It’s futile to try and build new land in the face of sea-level rise and subsidence……
ECOGEOMORPHOLOGY of Deltaic Coast
Wax Lake Delta – An analogue to study the
processes of a growing delta;
In contrast to Terrebonne & Lafourche that represent degrading stages of delta
.
SUMMARY: The Delta Mass Balance
The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter:
Atop the area of the delta
top
where H is eustatic sea level,
σ spatially averaged subsidence rate,
Qs total volumetric
sediment supply,
fr the fraction retained in
the delta top, and
rorg the rate of storage of
organic matter in the sediment column,
Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 1990
.
SUMMARY: The Delta Mass Balance
The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter:
Atop the area of the delta
top
where H is eustatic sea level,
σ spatially averaged subsidence rate,
Qs total volumetric
sediment supply,
fr the fraction retained in
the delta top, and
rorg the rate of storage of
organic matter in the sediment column,
Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2000
.
SUMMARY: The Delta Mass Balance
The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter:
Atop the area of the delta
top
where H is eustatic sea level,
σ spatially averaged subsidence rate,
Qs total volumetric
sediment supply,
fr the fraction retained in
the delta top, and
rorg the rate of storage of
organic matter in the sediment column,
Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2002
.
SUMMARY: The Delta Mass Balance
The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter:
Atop the area of the delta
top
where H is eustatic sea level,
σ spatially averaged subsidence rate,
Qs total volumetric
sediment supply,
fr the fraction retained in
the delta top, and
rorg the rate of storage of
organic matter in the sediment column,
Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2005
MIGRATION OF THE MODEL FROM WAX LAKE TO THE MISSISSIPPI RIVER BELOW NEW ORLEANS:
Two diversions: Barataria Bay and Breton Sound (Envisioning the Coast)
BASE CASE: SEA-LEVEL RISE = 2 mm/yr, SUBSIDENCE = 5 mm/yr = 918 km2
Solid line: variant caseDotted line: base case
“Worst case”:
still 701 km2 of new land
And extra land-building due to organics is not yet included
Developing a Self-Maintaining Coast is Possible
VARIANT CASE: SEA-LEVEL RISE = 4 mm/yr, SUBSIDENCE = 10 mm/yr = 701 km2
A New Approach to River Management for the 21st Century
Captain A. A. Humphreys
Lieutenant H. L. Abbot
Delta Report
19th Century River Management19th Century River Management
Tributary Basin Improvements
Levees
Floodways
Channel Stabilization
20th Century River ManagementMississippi River & Tributaries Project
20th Century River ManagementMississippi River & Tributaries Project
21st CenturyProtection, Restoration
AND Navigation
Main Points• Morganza can balance protection and
restoration – we have to make sure it does• Levees are not the only thing we need to do
to protect ourselves• Sustainable restoration takes bold action and
will mean change• 20th century - change for the worst• 21st century – change for the better?