September 14, 2021

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Brittany Girardeau, Amanda Taylor, and William Templeton to Present on Coastal Resiliency at 2021 National Coastal Conference

Brittany Girardeau, P.E. (Alabama), Amanda Taylor, P.E. (Louisiana), and William Templeton, P.E. (Oregon) will present on coastal resiliency at the 2021 National Coastal Conference at the Hilton Riverside in New Orleans, Louisiana on September 28-October 1, 2021.

Brittany Girardeau is a Staff Engineer with experience in coastal engineering and modeling. She frequently works in the development of watershed management plans, the analysis of various types of data, and the design of drainage areas. Throughout her career, Brittany has performed scour analysis, hydrologic modeling, hydrodynamic modeling, bridge superstructure and substructure load calculations, watershed management plan development, and design and calculation package development on various projects.

Amanda Taylor is an Engineer with extensive experience in the design and construction of coastal restoration projects. Her experience includes developing cost estimates and scopes of work for data collection; conducting design calculations, including tidal datum, relative sea level rise, and dredge volume calculations; and producing design reports, construction bid documents, and presentations to stakeholders.

William Templeton is an Engineer with experience in coastal, hydraulic, and civil engineering. He has worked on a wide variety of projects that include dredge analysis and design; coastal restoration; estuarine, coastal, and ocean circulation; wind/wave, sediment transport, and morphological numerical modeling; computational fluid dynamics modeling in support of scour analyses and wave and current force analyses of in-water structures; and analysis and design of coastal structures such as revetments, breakwaters, groins, seawalls, and jetties.

The theme of the 2021 conference, "Geaux Resilient," continues to broaden focus across the entire physical coastal and estuarine system. The National Coastal Conference provides an opportunity for coastal stakeholders and managers to develop collaborative networks to promote best management practices, while learning the latest science, engineering, and policy needed to maintain and improve the health of our beachfront and estuarine shorelines and ecosystems.

Since 1926, the American Shore and Beach Preservation Association (ASBPA) has made an organized effort to combat erosion, a serious problem in many coastal areas. ASBPA is dedicated to preserving, protecting, and enhancing the coasts by merging science and public policy. Its members advocate for healthy, sustainable, and resilient coastal systems to sustain four interconnected core values provided by shores and beaches: community protection, a strong economy, ecologic health, and recreation.

Geosyntec Participation

Coastal Modeling the Dauphin Island Causeway Vulnerability
Speaker: William Templeton, Brittany Girardeau, Geosyntec Consultants
Authors: William Templeton, Stephanie Smallegan, Wade Burcham, Geosyntec Consultants
Date and time: Sept. 30, 2021 at 4:30-4:50 p.m. CDT

Dauphin Island is a barrier island located in south Mobile County, Alabama and is home to approximately 1,324 residents. The Dauphin Island Causeway is the only road that residents and tourists have to commute to and from the island. The causeway is also Dauphin Island's only hurricane evacuation route. The causeway and surrounding areas are vulnerable to damage from storm events such as road inundation by flood waters, displaced armor stone from the hardened shoreline, and loss of wetlands. The vulnerability of the causeway to damage will only increase as sea levels rise.

The objective of the Dauphin Island Causeway Shoreline Restoration Project is to create and enhance the aquatic and wetland habitat and to increase the causeway's vulnerability to natural disasters. To achieve these objectives, a restoration project was designed for a 3.2-mile stretch of shoreline along the eastern side of the causeway. The overall site was characterized by wave conditions typically observed and divided into two regions: the 1.1 mile-long moderate wave energy shoreline (North) and the 2.1 mile-long high wave energy shoreline (South). The design for the north shoreline consists of tidal marsh, wave attenuation structures, and sand berms. The design for the south shoreline consists of tidal marsh, wave attenuation structures, curved breakwaters, and oyster coves.

This presentation will describe the methods and tools used to assess the causeway's vulnerability to storm conditions and the impacts of each design on the vulnerability. The results for such analysis will also be discussed.

The response of both the existing and proposed design conditions to a representative typical month – September of 2019 – were established by evaluating hydrodynamics and sediment transport at the site using Delft3D-Flexible Mesh, a coupled 2D circulation, wind/wave, and sediment transport and morphological model. The model was forced using measured tides from tide gauges near Dauphin Island and Pascagoula, MS, river discharge at the head of Mobile Bay scaled from Escambia River discharge, and measured wind velocities from a NOAA station near Dauphin island. In addition to the representative model, a suite of SWAN models was developed to evaluate the effectiveness of the design on attenuating waves sufficiently to support growth of proposed marshes under varying sea level rise scenarios.

XBeach, a 2D morphological model, was used to simulate the morphological change at the shorelines during a 25-year design event. A return period analysis of winds at Dauphin Island was conducted to establish the 25-year wave condition at the site using SWAN. A spatially varying grid representing each shoreline's initial, constructed, and 20-year settled bathymetry was created. The hydrodynamics and morphological change were modeled on these grids to estimate the causeway's vulnerability to the design storm event before and after project designs are implemented. The results produced are currently being analyzed and evaluated and are expected to be discussed during the presentation.

Road to Resiliency: Update on the Restoration of the Dauphin Island Causeway Shoreline
Speaker: Amanda Taylor, Geosyntec Consultants
Authors: Wade Burcham, Geosyntec; Tina Sanchez, Mobile County Commission; Matthew Jones, Mobile County
Date and time: Sept. 30, 2021 at 4:30-4:50 p.m. CDT

The Dauphin Island Causeway, which is located along the western shores of Mobile Bay, Alabama, serves as a critical transportation corridor and the sole roadway to Dauphin Island. Shoreline erosion, loss of wetlands, rising sea levels, and coastal storms battering the shore have degraded the shoreline along this important transportation link.

The goal of the Dauphin Island Causeway Shoreline Restoration Project is to increase community and ecological resilience by protecting the existing shoreline and restoring habitat function to areas of eroded intertidal marsh by design of a 3.2-mile-long living shoreline. Restoration includes the construction of approximately 100 acres of tidal marsh, wave attenuation structures, and oyster coves.

The appropriate arrangement, elevation, and composition of wave attenuation structures; appropriate marsh elevations; and depth, slope, and arrangement of tidal channels were determined through a combination of stakeholder engagement, hydrodynamic and sediment transport modeling, field reconnaissance data, and multiple data collection events.

This presentation will discuss design and constructability considerations of the project.

More Information

About the event: 2021 National Coastal Conference
About the American Shore and Beach Preservation Association: https://asbpa.org/
For consultation regarding coastal resiliency, contact Amanda Taylor at This email address is being protected from spambots. You need JavaScript enabled to view it. or William Templeton at This email address is being protected from spambots. You need JavaScript enabled to view it.
Learn more about Amanda: Brittany Girardeau – LinkedIn
Learn more about Amanda: Amanda Taylor – LinkedIn
Learn more about William: William Templeton – LinkedIn