Healthy Coastal Ecosystems
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Robert Twilley, vice chancellor of research, University of Louisiana at Lafayette. Sea Grant Week 2010
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Healthy Coastal Ecosystems
- 1. LANDSCAPES ON THE EDGE: THE MISSISSIPPI RIVER DELTA RESTORATION
- 2. Trees Aged at 250 yrs Disturbance Reorganization
- 3. Displaced 700,000 Homes destroyed 130,000 Dead 246 The Great Flood 1927 John Stewart Curry Hoover and the Flood 1940 Library of Congress
- 4. 1947 Fisk Map of the river’s historic course 1958 River Flood Capacity Diagram The Transformation of the River: From Flux to Control
- 5. MR&T Flood Control Act of 1928
- 6. The Transformation of the River: From Flux to Control 1947 Fisk Map
- 9. Historical Basins of the Mississippi River
- 11. 5. Major Disturbance to social systems; included floods and hurricane events; flooding that threaten public safety and economic development – Federal Responsibility and Response Built Infrastructure
- 12. Annual report of Paul Octave Hebert, State Engineer to the Louisiana Legislature, Jan. 1847 Civil engineers Paul Octave Hebert and Absalom D. Woodridge supported a diversified approach to flood control that depended on the combination of outlets and levees. They criticized current measures that relied solely on levees to prevent overflow. By urging the state to adopt new policies aimed at keeping open the last few remaining outlets and building artificial ones to replace those already lost, state engineers tried to temper the drive of many planters to remake the river.
- 13. 13 1: The Atchafalaya Floodway represents major section of flood control system Roberts et al. 19971912 1930 1960 1975
- 14. 1: The Atchafalaya Floodway represents major success in delta formation
- 15. THE WAX LAKE DELTA AS ANALOGUE OF HOW TO REBUILD A DELTA 1990 2005 Wonsuck Kim, Gary Parker, David Mohrig, Robert Twilley, EOS 2009
- 16. MIGRATION OF THE MODEL FROM WAX LAKE TO THE MISSISSIPPI RIVER BELOW NEW ORLEANS: Two diversions: Barataria Bay and Breton Sound (for demonstration purposes)
- 17. Worse Case: SEA-LEVEL RISE = 4 mm/yr, SUBSIDENCE = 10 mm/yr (701 km2) Solid line: variant case Dotted line: base case Developing a Self-Maintaining Coast is Possible Base Case: SEA-LEVEL RISE = 2 mm/yr, SUBSIDENCE = 5 mm/yr (980 km2)
- 18. SEA LEVEL Tidal/River Flooding Nutrient Input PRIMARY PRODUCTION Increase Sea Level SUBSIDENCE
- 19. Managing River and Coastal Processes linked with Engineering Design to Develop a Self- Maintaining Delta Landscape (footprint)
- 20. Sand - Silt – Salt - Nitrate Tradeoffs of Rebuilding Deltaic Coasts Salinity LAND Nutrients
- 21. Catchment to the Coast: Hubbard Brook Type Coastal Ecosystem Studies
- 22. SCIENCE, 27 August 2005 Katrina 2005
- 23. 23 Healthy very tall wetlands being cut for the access channel of the MRGO (Mississippi River Gulf Outlet) EXTENSIVE CYPRESS SWAMPS EXTENSIVE AREAS OF REED SWAMPS 5-6 M HIGH
- 26. 5. Major Disturbance to social systems; included floods and hurricane events; flooding that threaten public safety and economic development – Federal Responsibility and Response Built Infrastructure
- 28. 1. Regional coastal ‘hubbard brooks’ – case studies of regional trends as research, education, and outreach opportunities.Goal: Widespread use of ecosystem-based approaches to managing land, water and living resources in coastal areas. Goal: Restored function and productivity of degraded ecosystems. Goal: Sound scientific information to support ecosystem-based approaches to managing the coastal environment. Healthy Coastal Ecosystems 3. Catchment to the Coast: Have to leverage with other professional units within university land grant system – and beyond ! 2. Calibrate Cause and Effect: Synthesis of long term trends at ecosystem level –build confidence in how we restore coastal ecosystems (diagnostics vs prescription). 4. Plan for the Reorganization Phase: Be prepared with variety of coastal hazards to provide clear, sound, and balanced ecosystem perspectives.
- 29. Coastal Sustainability Studio LSU Sponsored by the America Wetlands Foundation with support from Chevron Corporation
- 30. Goals Building with Nature - self sustaining ecosystems Intelligent storm and flood protection Productive innovative economy Dynamic and sustainable community Bayou Bienvenue
- 31. Baton Rouge New Orleans Atchafalaya River Basin Lake Charles Lafayette Houma Old River Control Gulf of Mexico Managing the Mississippi: Flood Control that Compliments Restoration
- 32. Baton Rouge New Orleans Atchafalaya River Basin Lake Charles Lafayette Houma Old River Control Gulf of Mexico
- 33. Managing the Mississippi: From Flood Control to Controlled Flood Baton Rouge New Orleans Atchafalaya River Basin Lake Charles Lafayette Houma Old River Control Gulf of Mexico Wax Lake Diversion Terrebonne Diversion Bayou LaFourche Diversion Davis Pond Diversion MRGO/LaLoutre Diversion
- 34. Building on the Urban Edge: Lower 9th Ward Wetland Center
- 35. Building on the Urban Edge: Lower 9th Ward, New Orleans
- 36. Design Process Stage 4: Scenarios Industry and Jobs Wetland regenerationRecreationHousing and Neighborhoods The Productive Landscape Scenario 1 Scenario 2 Scenario 3
- 37. The Transformation of the River: The Future
Editor's Notes
- The previous two subject areas are ‘new in themselves’. This one seems to be the most traditional: basins are the heart of sed/strat, landscapes the heart of geomorph. But...
- In 1874, after years of failed attempts at dredging, levee building and debate about constructing a canal, James Eads proposed building large Jetties along the outlet of the river.
- This map shows the various course of the river as it navigated the delta over thousands of years.
- But as impressive as the jetties were for the movement of goods in through the mouth of the river, even more dramatic was the change it encapsulated for the treatment of the River throughout the delta region. The 1879 creation of the Mississippi River Commission, with Eads as one of its most prominent members took on the huge roll of controlling and bending the entire purpose of the river.
- Thresholds of deltaic coast Ecosystem state change is the conversion of wetlands to open water – wetland loss – 44 km2 per year - Associate concepts related to thresholds of restoration; contrast to most of the talks on eutrophication
- It is as if two separate objectives are functioning but in sequence. The first maximizes production and accumulation The second maximizes invention and reassortment. The two objectives can not be maximized simultaneously but only occur sequentially. The adaptive cycle therefore embraces two opposites: growth and stability on the one hand and changes and variety on the other.
- Wax position to Atch Both emerged in 1973 Wax has more natural channel and island development Atch influenced by dredge spoil islands for navigation channel maintenance Per unit discharge, higher exposure of flow to wetland areas, more energetic
- Wetlands in deltaic coast must have capacity to adapt to rise is sea level; and along LA coast there is also change in water levels caused by land sinking Relative rise in sea level is the combined effect of sea level and subsidence – important threshold change in elevation and thus water levels Thus adaptation for wetlands is to maintain surface elevation equal to the annual change in relative sea level If not, then wetland drowns and converts to open water – condition of degradation
- The other adaptation is the supply of sediment that is linked to management of river – two effects One - There has been reduction of sediment delivery to the floodplains – restricted to flow out to GOM – see diagram Second – there is reduction of sediment from the river basin – see statistics Thus – sediment supply to provide capacity for wetlands to adapt has been reduced this reduces the capacity to reach critical thresholds of accretion or elevation to counter effects of relative sea level rise
- It is as if two separate objectives are functioning but in sequence. The first maximizes production and accumulation The second maximizes invention and reassortment. The two objectives can not be maximized simultaneously but only occur sequentially. The adaptive cycle therefore embraces two opposites: growth and stability on the one hand and changes and variety on the other.
- As essential to the construction of the delta as the river was, the river’s absence is rapidly leading to its disappearance.