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Storm Protection & Coastal Restoration: Moving in to the 21 st Century

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

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Storm Protection & Coastal Restoration: Moving in to the 21 st Century

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  1. Storm Protection & Coastal Restoration: Moving in to the 21st Century Denise J. Reed University of New Orleans Restore or Retreat March 2009

  2. 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

  3. 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

  4. Houma N Federal Levee Alignment Work in Kind (WIK) Levees Sector Gates Larose GIWW Presquile GIWW Bourg REACH L Ashland 56 REACH A Montegut Chauvin REACH K REACH B REACH J Boudreaux 315 B. Petit Caillou B. Terrebonne Dulac REACH E REACH J-1 REACH I Lafourche Parish REACH F 55 B. Lafourche 57 REACH H REACH G B. Grand Caillou Terrebonne Parish Cocodrie Morganza to the Gulf of Mexico Project Houma Navigation Canal Lock

  5. Wetlands Behind Levees = Opportunities? MINORS CANAL REACH L REACH A REACH B REACH J REACH K REACH I REACH E REACH F REACH H REACH G REACH H-1

  6. More tidal exchange = more opportunity for sediment input Existing levees Roads Existing levees

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. USACE Slide courtesy of Pete Rabbon

  12. 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.

  13. 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.

  14. 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

  15. The Past

  16. Continuing Current Management

  17. Achieving Sustainability

  18. Coast 2050

  19. 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……

  20. 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

  21. SUMMARY: The Delta Mass Balance The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter: Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 1990 Atopthe area of the delta top where His eustatic sea level, σ spatially averaged subsidence rate, Qstotal volumetric sediment supply, frthe fraction retained in the delta top, and rorgthe rate of storage of organic matter in the sediment column, .

  22. SUMMARY: The Delta Mass Balance The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter: Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2000 Atopthe area of the delta top where His eustatic sea level, σ spatially averaged subsidence rate, Qstotal volumetric sediment supply, frthe fraction retained in the delta top, and rorgthe rate of storage of organic matter in the sediment column, .

  23. SUMMARY: The Delta Mass Balance The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter: Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2002 Atopthe area of the delta top where His eustatic sea level, σ spatially averaged subsidence rate, Qstotal volumetric sediment supply, frthe fraction retained in the delta top, and rorgthe rate of storage of organic matter in the sediment column, .

  24. SUMMARY: The Delta Mass Balance The Dynamic Delta Top = competition between sea-level rise + subsidence and deposition of sediment and organic matter: Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, submitted 2005 Atopthe area of the delta top where His eustatic sea level, σ spatially averaged subsidence rate, Qstotal volumetric sediment supply, frthe fraction retained in the delta top, and rorgthe rate of storage of organic matter in the sediment column, .

  25. MIGRATION OF THE MODEL FROM WAX LAKE TO THE MISSISSIPPI RIVER BELOW NEW ORLEANS: Two diversions: Barataria Bay and Breton Sound (Envisioning the Coast)

  26. BASE CASE: SEA-LEVEL RISE = 2 mm/yr, SUBSIDENCE = 5 mm/yr = 918 km2 VARIANT CASE: SEA-LEVEL RISE = 4 mm/yr, SUBSIDENCE = 10 mm/yr = 701 km2 Solid line: variant case Dotted line: base case And extra land-building due to organics is not yet included “Worst case”: still 701 km2 of new land Developing a Self-Maintaining Coast is Possible

  27. A New Approach to River Management for the 21st Century

  28. 19th Century River Management Captain A. A. Humphreys Delta Report Lieutenant H. L. Abbot

  29. 20th Century River Management Mississippi River & Tributaries Project Channel Stabilization Levees Tributary Basin Improvements Floodways

  30. 21st Century Protection, Restoration AND Navigation

  31. 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?

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