Physical & Program Options for Inland Migration of Louisiana s Coastal Wetlands

Transcription

1 Physical & Program Options for Inland Migration of Louisiana s Coastal Wetlands Melissa Kemm & Sam Pardo Duke University Nicholas School of the Environment Client: Louisiana Coastal Protection & Restoration Authority (CPRA)

2 Goals of the Master s Project What areas in coastal Louisiana can serve as future wetland sites? What policy alternatives are available to facilitate the migration of wetlands? 1. Wetland loss in Louisiana 2. Geospatial modeling of sea level rise (SLR) & wetland migration 3. Policy analysis 4. Bringing it all together applying policy tool to geospatial results 2

3 Louisiana s Coastal Wetlands 40% 4,680 Square miles Adapted from CPRA

4 History of Wetland Loss 100+ Years of Land Change for Coastal Louisiana 1,800 Square miles 4

5 Case Studies & Site Selection Vermilion St. Mary Lafourche 5

6 Parish Comparisons Lafourche Vermilion St. Mary 6

7 Sea Level Affecting Marshes Model (SLAMM) Inputs Landcover Elevation Slope Dikes/Levees Parameters Subsidence Tide Range & Frequency of Inundation Erosion & Accretion Rates Warren Pinnacle 7

8 SLAMM Scenarios Inputs & Parameters Low Subsidence High Subsidence Dikes No Dikes SLR by meters 1.0 meters 1.5 meters 2.0 meters 8

9 SLAMM Results Vermilion St. Mary Lafourche meter SLR by 2100, Dike Protection, Low Subsidence 9

10 Wetland Loss (Ha) Wetland Loss (Ha) Wetland Loss (Ha) Model Sensitivity to Subsidence & Protection Conditions 100,000 Vermilion Parish 60,000 St. Mary Parish 80,000 50,000 60,000 40,000 40,000 30,000 20,000 20, ,000-20, SLR by 2100 (m) SLR by 2100 (m) 180, , , , ,000 80,000 60,000 40,000 20,000 0 Lafourche Parish SLR by 2100 (m) Low Subsidence & Dike Protection High Subsidence & Dike Protection Low Subsidence & No Dike Protection High Subsidence & No Dike Protection 10

11 Upland Migration of Wetlands Vermilion St. Mary Lafourche meter SLR by 2100, No Dike Protection, Low Subsidence 11

12 Area (Ha) Area (Ha) Area (Ha) Area (Ha) Undeveloped Dry Land Converting to Wetlands 25, m SLR by , m SLR by ,000 20,000 15,000 15,000 10,000 10,000 5,000 5, , m SLR by , m SLR by ,000 20,000 15,000 10,000 5,000 15,000 10,000 5, Vermilion St. Mary Lafourche 1.5 meter SLR by 2100, No Dike Protection, Low Subsidence 12

13 Modeling Results Summary Protection of dry land Wetland migration Allowing migration may not result in equal benefits across the study sites Management decisions must consider variability along the coast 13

14 Coastal Protection and Restoration Authority (CPRA) Adapted from CPRA (2012) 5-year Cycle Induced Risk 14

15 Policy Alternatives Regulatory Programs Rolling Easements Density Restrictions Transferable Development Rights Voluntary Options Conservation Easements Defeasible Estates Voluntary Acquisition 15

16 Policy Criteria Primary Wetland Migration Flood Risk Practical Equity Adaptability Political Feasibility 16

17 Potential Wetland Migration Wetland Gain (sq. mi.) Wetland Loss (sq. mi.) % Loss Offset by Gain Vermilion % St. Mary % Lafourche % Vermilion Migration Lafourche Migration 17

18 Using Matrix as Decision Support Tool Regulatory Programs Voluntary Options Criteria Sub-Criteria Rolling Easements Zoning Restrictions Transferable Development Rights Conservation Easements Defeasible Estates Voluntary Acquisitions Wetland Migration Prevent Property Armoring Minimize Development Flood Risk Reduction Minimize Assets at Risk Social Equity Equity Protection of Property Rights Adaptability Maximize Flexibility of Outcomes Political Feasibility Regulatory Precedent Popular Sentiment 18

19 Expect the Unexpected Adapted from CPRA (2012) 19

20 Conclusions Wetland migration can reduce, but not fully offset wetland loss by 2100 Levee protection of undeveloped dry land is the greatest impediment to migration HOWEVER removing levees does not help facilitate wetland migration in every case A wetland migration policy can help mitigate wetland loss AND address induced risk Social, political, and environmental factors need to be considered at the finest grain possible 20

21 Thank you for your attention. Questions?

22 Total Land in Coastal Study Area (Square Miles) Future of Wetland Loss Optimistic Scenario 5000 Maximize Land Future Without Action Adapted from CPRA

23 Vermilion Parish in 2100 No Dike Protection Dike Protection Low Subsidence (4 mm/yr) High Subsidence (6 mm/yr) 1.5 meter SLR by 2100, Low Subsidence 23

24 Project Types Restoration Total: $50 Billion Structural Protection Nonstructural Protection $12.9 Billion Barrier Islands Sediment Diversions Hydrologic Restoration Marsh Creation Levees Floodwalls Flood Proofing Elevating Structures Voluntary Acquisition Wetland Migration 24

25 Policy Approach Prescriptive Problem Model Evaluate Decision vs. Exploratory Define Search Problem Decision Select Evaluate 25