Sea-Level Rise and Coastal Habitats in Southeastern Louisiana An Application of the SLAMM Model

Sea-Level Rise and Coastal Habitats in Southeastern Louisiana An Application of the SLAMM Model Patty Glick (National Wildlife Federation) Jonathan Clough (Warren Pinnacle Consulting, Inc.) Amy Polaczyk (Warren Pinnacle Consulting, Inc.) Brad Nunley (Independent GIS Contractor)

A Focus on Sea-Level Rise

Louisiana Model Uses Which Marsh Lands are Predicted to be Most Vulnerable/Resilient? Critical question when planning marsh restoration efforts Model Can be Used to Examine Alternative Management Actions What if analyses for subsidence or accretion rates Given predicted changes in sediment input, how does this affect marsh resilience spatially?

SLAMM SE Louisiana Study Area (15-meter cells, 39,000 square km)

Hindcast and Forecast Model Validation (Hindcast) Purpose of this exercise is to run the model, starting in 1956 with the best available 1956 data, and examine results against the current (2007) data Model Calibration (Hindcast) Start with model validation, examine model parameters and modify them (within feasible range) to gather best possible simulation Key variables: Floating marsh and accretion rates Calibrated Model Serves as Basis for Forecasting

Digital Elevation Map (Provided by Brady Couvillion, USGS)

Wetland Coverage (2007) (Provided by Brady Couvillion, USGS)

Hurricanes

Wetland Coverage (2007) (Provided by Brady Couvillion, USGS)

Areas Protected by Dikes (dry land also assumed protected )

Spatially Variable Subsidence Rates (From Shinkle and Dokka 2004) 1.5 mm/y ear 1.5 mm/y ear 15 mm/year

Map of Subsidence Rates

Flotant Marsh 13

Accretion Data Based on Peer-Reviewed Literature Average value approx. 8.2 mm/yr Exception: areas known for higher accretion (Atchafalaya River Basin, Delta)

Accretion Data SLAMM 6 Allows Accretion Feedback Accretion rates higher in areas of lower elevation Feedback not used for floating marshes

Cypress and Flooded Swamp

Erosion/Overwash Did not calibrate model to beach or marsh erosion Limited beach area, focus on marshes. Significant complexity uncertainty in response of barrier islands Erosion not considered major factor in marsh loss (with some exceptions) SLAMM model less sensitive to erosion rate parameters 17

Hindcast Results Percentage of land cover lost between 1956 and 2007 as predicted and observed Land cover type WEST EAST TOTAL Predicted Observed Predicted Observed Predicted Observed Salt Marsh 12% 19% 33% 28% 25% 25% Fresh Marsh 41% 44% 53% 79% 45% 57% Total Marsh 28% 33% 40% 44% 34% 39% Swamp 41% 13% 60% 56% 46% 24% Beach 99% 56% 94% 84% 96% 76% Salt Marsh category includes regularly and irregularly-flooded marsh Fresh Marsh includes inland and tidal fresh marsh Swamp includes swamp and cypress swamp

Forecast: SLR scenarios

Forecast: SLR scenarios examined 200 Eustatic SLR (cm) 160 120 80 40 Upper-End (1.90 m) Most likely (1.22 m) Lower-End (0.75 m) Rapid Stabilization (0.34 m) 0 1980 2000 2020 2040 2060 2080 2100 2120

Forecast Results Square Miles of Wetland Loss SQ MI SLR by 2100 (m) 2025 2050 2075 2100 0.34 (linear) 114 298 544 816 0.75 124 505 1,114 1,614 1.22 163 844 1,449 1,995 1.9 243 1,089 1,627 2,238

Forecast Results Percent loss of specific wetland types SLR by 2100 (m) 0.34 meters 0.75 meters 1.22 meters 1.9 meters Cypress Swamp x 66% 86% 93% 96% Regularly Flooded Marsh -6% 42% 55% 71% Irregularly Flooded Marsh 48% 71% 78% 87% Swamp 53% 61% 68% 74% Tidal Fresh Marsh 30% 66% 91% 96% Inland Fresh Marsh 42% 73% 86% 88% Tidal Swamp 95% 98% 99% 99% Estuarine Beach 82% 86% 88% 89% x Cypress swamp loss includes cypress swamp that becomes permanently flooded.

Vulnerability of Habitats Brackish and Intermediate Marsh Particularly vulnerable, even under low scenarios Salt marsh in some areas appears relatively resilient under low scenario (likely due to land growth at Atchafalaya)

Vulnerability of Habitats Cypress-Water Tupelo Swamps Appears highly vulnerable. May endure as flooded swamp for decades, but will no longer be able to regenerate Flotant Appears relatively resilient, but high level of uncertainty

Initial Condition Start date = 2007 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

0.34-Meter Scenario 2025 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

0.34-Meter Scenario 2050 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

0.34-Meter Scenario 2075 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

0.34-Meter Scenario 2100 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

1.22-Meter Scenario 2025 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

1.22-Meter Scenario 2050 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

1.22-Meter Scenario 2075 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

1.22-Meter Scenario 2100 Estuarine Open Water Estuarine Open Water Swamp Swamp Estuarine Beach Estuarine Beach Cypress Swamp Cypress Swamp Tidal Fresh Marsh Tidal Fresh Marsh Transitional Salt Marsh Transitional Salt Marsh Undeveloped Dry Land Undeveloped Dry Land Inland Fresh Marsh Inland Fresh Marsh Inland Open Water Inland Open Water Regularly Flooded Marsh Regularly Flooded Marsh Developed Dry Land Developed Dry Land Flooded Swamp Flooded Swamp Irregularly Flooded Marsh Irregularly Flooded Marsh Tidal Swamp Tidal Swamp Tidal Flat Tidal Flat

Remedial Alternative Caernarvon Diversion

Remedial Alternative Caernarvon Diversion 46

Marsh Loss With/Without Diversion (2050)

Marsh Loss With/Without Diversion (2100)

Management Considerations Prioritize Projects Based on Ecological Importance and Vulnerability Consider sea-level rise impacts when making decisions regarding harvest and carbon sequestration efforts in cypress swamps

Management Considerations Restore and Protect a Diverse Array of Habitat Types to Support Ecosystem Function Brackish and intermediate marshes subject to significant losses More research necessary to assess potential impacts on flotant

Management Considerations Identify Areas That Might Warrant Specific Strategies Such as Replenishment of Sediments Atchafalaya Delta looks highly resilient under all but highest scenario Results of remedial alternative exercise suggest potential benefit of diversions

Management Considerations Expand Restoration and Protection Strategies to Accommodate for Habitat Migration Additional research on land use and infrastructure vulnerability will help managers identify candidate areas for easements, other strategies