Alabama Barrier Island Restoration Assessment


Description

This project is a collaborative effort between the USGS, U.S. Army Corps of Engineers (USACE), and the State of Alabama funded by National Fish and Wildlife Foundation (NFWF) to investigate viable, sustainable restoration options that protect and restore the natural resources of Dauphin Island, Alabama. The project is focused on restoration options that protect and restore habitat and living coastal and marine resources, as well as protect the coastal resources of the Mississippi Sound/Mobile Bay and the southern portion of Mobile County including the expansive Heron Bay wetlands. Data collection and modeling will be used to evaluate restoration actions with regards to resiliency and sustainability in support of critical habitats and resources.

Objectives

Joint Study Project Objectives are under development.

  • The overarching goal is to preserve and enhance the ecological functions and values of the island and associated estuarine resources the barrier island helps to maintain.
Background

Dauphin Island, Alabama, is a strategically significant barrier island along the northern Gulf of Mexico and, more specifically, serves as the only barrier island providing protection to much of the state of Alabama’s coastal natural resources. The size of the system spans over 200 acres of barrier island habitat including beach, dune, overwash fans, intertidal wetlands, maritime forest, and freshwater ponds. In addition, Dauphin Island provides protection to approximately one-third of the Mississippi Sound and estuarine habitats including oyster reefs, marshes and seagrasses. The island has been severely impacted by repeated extreme events over the past several centuries, most recently Hurricanes Ivan, Katrina, and Isaac, and by the Deepwater Horizon oil spill. The State of Alabama, the USGS, and the USACE are conducting a joint study to evaluate feasibility level alternatives to increase resiliency and sustainability of Dauphin Island.

Methods

USGS Tasks

Task 1.1 Data Compilation. Existing datasets will be compiled and cataloged.
Task 1.2 Database Development. Data formats will be leveraged, developed, standardized, and documented.
Task 1.3 Tool Development for Analyses. A web mapping application will be developed to visualize, spatially search, and disseminate the Dauphin Island data.
Task 2.1 Bathymetric and Geophysical Surveys. Bathymetric and stratigraphic characterization of Dauphin Island and surrounding waters will be conducted to evaluate the physical environment including surface elevations, morphology, habitat, and geologic framework.
Task 2.4 Sediment Distribution. Characterization of sediment texture, including detailed grain size metrics, within coastal-zone environments will be obtained in order to evaluate relationships among sediment-transport patterns, alongshore variability, geotechnical properties that influence the development of shoreline nourishment and restoration approaches, and for inclusion in models to help anticipated coastal-system response to storm events.
Task 2.5 Water Quality. Water quality and sediment data will be collected 8 times at four locations in the Mississippi Sound of Dauphin Island to update existing baseline conditions and provide needed data for modeling efforts.
Task 3.1 Gulf Facing Shoreline. An updated analysis of historical and present day Gulf facing shoreline positions will provide the basis for assessing short-term and long-term shoreline change along the coast. Analysis will include the combination of historical beach profile surveys and historical aerial photography conducted in previous studies as documented in Byrnes et al., 2010 and 2012. GIS shapefiles will be produced and available for volumetric change analysis.
Task 3.2 Estuarine Shoreline and Environments. The project will examine changes in back-barrier estuarine shoreline to derive trends in shoreline erosion/accretion, island width, and increases or decreases in vegetated communities.
Task 3.3 Habitat Mapping. High-resolution, aerial imagery, and a baseline habitat map will be developed to establish a baseline of the habitat extent within the study area.
Task 5.1 Hydrodynamic and Morphological Change Modeling. A numerical model of coastal processes will be developed for Dauphin Island using a coupled Delft3D and XBeach modeling approach.
Task 5.4 Habitat Modeling. Modeling and assessment of habitats and vegetative units for time-steps for long-term scenario analyses using contemporary relationships (i.e., elevation and landscape position) to produce habitat maps and acreages for geomorphologic scenarios.
Task 6.2 Alternative Assessment Tool Development. Results of modeling and expert opinion will quantify the consequences of each alternative relative to natural resource benefit, the likelihood of project success, and the impact to coastal protection, as well as other objectives that will be elicited from the appropriate stakeholders and decision-makers.
Task 7 Monitoring and Adaptive Management. A monitoring and adaptive management plan and a conceptual ecological model will be developed for the project.
Task 9 Project Management and Coordination.
Data Synthesis
  • Characterize the morphology and geologic framework of the inner shelf, Mobile Pass ebb-tide delta, and Mississippi Sound.
  • Provide information necessary for locating and evaluating sediment resources suitable for island restoration efforts.
  • Provide up-to-date water quality data for modeling, restoration design, and coastal management related to elevation, sediment and water quality.
  • Characterize longshore and cross-shore variability in sediment characteristics that will allow assessments of the hydrodynamic zonation of sediments around the island and associated passes and that may be used to help evaluate habitat distribution and vegetation composition on the island and associated flats.
  • Data will be used to support sediment distribution and recent changes in sediment transport pathways, erosion, and accretion relevant to managing, maintaining and restoring island shoreline and habitat.
  • Evaluation of the change and rate of change for shoreline as well as the relative vertical elevation changes through time and historical marsh accumulation rates.
  • A baseline of habitat extent within the study area including a map of habitats important to identified species and ecosystem endpoints (e.g., sea turtles, shorebirds, and neotropical migrant birds).
  • Hydrodynamic and morphological modeling to support evaluation of restoration alternatives based on a comprehensive analysis of nearshore wave transformation, tidal hydrodynamics, and sediment transport.
  • A habitat geospatial model will be linked to the geomorphological model to help quantify habitat units for proposed restoration alternatives allowing will allow for assessment of habitat and living resource benefits and/or impacts from proposed restoration alternatives into the future.
  • Development of a tool to evaluate trade-offs among developed alternatives as related to overall project goals (e.g., habitat for at-risk populations, probability of persistence of migratory birds, protection of wetlands).
  • A conceptual ecological model (CEM) will be developed and used to represent current understanding of ecosystem structure and function in the project area, identify performance measures, help select parameters for monitoring, and identify critical uncertainties.
References
  • Byrnes, M.R., Griffee, S.F., and Osler, M.S., 2010, Channel Dredging on Geomorphic Response at and Adjacent to Mobile Pass, Alabama, ERDC/CHL-TR-10-8, US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi. 309 p.
  • Byrnes, M.R., Rosati, J.D., Griffee, S.F., and Berlinghoff, J.L., 2012, Littoral sediment budget for the Mississippi Sound barrier islands: Vicksburg, Miss., U.S. Army Engineer Research and Development Center Technical Report ERDC/CHL TR-12-9, 106 p.
  • Lesser, G.R., Roelvink, J.A., Kester, J.A.TM. van, and Stelling, G.S., 2004, Development and validation of a three-dimensional morphological model: Coastal Engineering, v. 51, no. 8-9, p. 883-915.
  • Long, J.W., Plant, N.G., Dalyander, P.S., and Thompson, D.M., 2014, A probabilistic method for constructing wave time-series at inshore locations using model scenarios. Coastal Engineering, v. 89, p. 53-62.
  • Morton, R.A., 2008, Historical changes in the Mississippi-Alabama barrier-island chain and the roles of extreme storms, sea level, and human activities, Journal of Coastal Research, v. 24, no. 6, p. 1587-1600.
  • Park, Kyeong, Powers S.P., Bosarge, G.S. and Jung, Hoon-Shin, 2013, Plugging the leak - barrier island restoration following Hurricane Katrina enhances larval retention and improves salinity regime for oysters in Mobile Bay, Alabama. Marine Environmental Research, v. 64, p. 48-55.
  • Roelvink, Dano, Reniers, Ad, Dongeren, Ap van, Thiel de Vries, Jaap van, McCall, Robert, and Lescinski, Jamie, 2009, Modelling storm impacts on beaches, dunes and barrier islands: Coastal Engineering, v. 56, no. 11-12, p. 1133-1152.
  • Twichell, David, Pendleton, Elizabeth, Baldwin, Wayne, Foster, David, Flocks, James, Kelso, Kyle, DeWitt, Nancy, Pfeiffer, William, Forde, Arnell, Krick, Jason, and Baehr, John, 2011, The shallow stratigraphy and sand resources offshore of the Mississippi Barrier Islands (ver. 1.1, March 2014): U.S. Geological Survey Open-File Report 2011-1173, 63 p., at http://pubs.usgs.gov/of/2011/1173/. (Supersedes ver. 1.0 released August 4, 2011.)
  • Twichell, David, Kelso, Kyle, and Pendleton, Elizabeth, 2012, Evidence for mid-Holocene shift in depositional style in Mobile Bay, Alabama: U.S. Geological Survey Open-File Report 2012–1081, 17 p., available at http://pubs.usgs.gov/of/2012/1081/.