sessions 81-90
Thursday, May 22 | 12:30 – 2:00 p.m.
Sessions
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 286
#81 Port Fourchon & Coastal Restoration
Port Fourchon is a major intermodal transfer hub that supports 11,000 direct Louisiana jobs while servicing over 95% of the deep-water energy produced in the Gulf of Mexico, having a $46M daily impact to the energy industry. It is the base for over 250 companies including Edison Chouest Offshore port facilities, Bollinger Fourchon, Halliburton, Hornbeck Offshore, Harvey Gulf International, and the Louisiana Offshore Oil Port (LOOP). The creation and expansion of Port Fourchon has also walked hand-in-hand with coastal restoration and mitigation projects that both help restore the historical landscape and provide invaluable protection to critical infrastructure. The Greater Lafourche Port Commission (GLPC) is excited to share the status of a few of their projects that sit at the intersection of coastal protection and restoration, energy, interagency collaboration, and innovation. Topics covered in this session will include an overview of Port Fourchon expansion plans and previous coastal restoration and mitigation projects, nearby CWPPRA marsh creation projects, ongoing shoreline protection efforts, and the beneficial use of dredged materials (BUDM).
Moderator: Kyle Galloway – GIS Engineering
Presenters:
• Mariann Alvarez– GIS Engineering
• Andy Fontenot – GIS Engineering
• Amelie Lagarde– GIS Engineering
• Bryce Autin – Greater Lafourche Port Commission
BUDM: Sustainable Borrow Sources for Coastal Restoration
Mariann Alvarez– GIS Engineering
Due to significant relative sea level rise and disconnection from the Mississippi River, a large majority of Louisiana’s wetlands and beaches are experiencing sediment deficits and subsequent land loss. One coastal restoration effort, marsh creation, has often utilized offshore sand borrow areas to create/nourish marshes and beaches. Meanwhile, Louisiana has thousands of miles of navigable waterways that require occasional dredging to maintain water bottom elevations to facilitate vessel navigation and freshwater flows. The beneficial use of dredged material (BUDM) provides a sustainable borrow source for coastal restoration projects, and BUDM is often more cost-effective than collecting sand offshore/trucking in material for placement. Additionally, USACE has a vision to increase the practice of utilizing dredged sediments beneficially to 70% by 2030, as compared to historical 30-40% utilization. Therefore, BUDM efforts partnered with local stakeholders are a cost-effective and sustainable resource for Louisiana’s marsh creation projects. These restoration projects then provide further protection for critical infrastructure located along these navigable waterways, creating a beneficial feedback loop for the local communities of Louisiana.
CWPPRA Restoration Projects Around Port Fourchon
Andy Fontenot – GIS Engineering
There are two CWPPRA Restoration Projects near Port Fourchon: the West Fourchon Marsh Creation and Nourishment (TE-0134) Project and the Port Fourchon Marsh Creation (TE-0171) Project. These two projects work synergistically with other, already constructed CWPPRA projects that help protect critical infrastructure from storms and restore local ecosystems. Both projects will utilize beneficial use of dredged material (BUDM) from the navigable channel of Bayou Lafourche and/or Belle Pass. Both of these projects have had varying levels of engagement and collaboration from GLPC, CPRA, and CWPPRA federal agencies. Together the TE-0134 and TE-0171 projects would create and nourish over 1,000 acres of intertidal salt marsh within Timbalier Bay in the Terrebonne Hydrologic Basin.
Port Fourchon Shoreline Protection
Amelie Lagarde– GIS Engineering
There have been several federal-, state-, and locally-funded coastal restoration projects along the Caminada Headlands, between Port Fourchon and Grand Isle. This stretch of beach is the first line of defense for Port Fourchon, Hwy-1 evacuation route, and thousands of acres of back barrier marsh during storms. Ongoing and future shoreline protection projects in the area represent a continued investment into the protection of coastal resources, critical infrastructure, and previous restoration investments in this area. Discussion of current shoreline protection feasibility study and past marsh creation and breakwater projects.
Coastal Restoration and Future Endeavors for Port Fourchon
Bryce Autin – Greater Lafourche Port Commission | View Presentation
The Greater Lafourche Port Commission (GLPC), a political subdivision of the state of Louisiana, facilitates the economic growth of the communities in which it operates by maximizing the flow of trade and commerce. GLPC has several ongoing and future projects ahead to help fulfill their mission, including their Slip D Expansion, Fourchon Island Development, and investment in Offshore Wind Energy. Additionally, GLPC continues a long history of coastal restoration around Port Fourchon that both mitigates and protects the expansion of the Port. These mitigation and restoration projects help restore the historic landscape and ecosystems and increase outdoor recreation opportunities for the local community. Some of these projects include the Coastal Wetlands Park, Maritime Forest Ridge and Marsh Restoration, Fourchon Beach Repair Project, and Port Fourchon Northern Expansion. As Port Fourchon continues to expand, GLPC is committed to continue to find the balance between industry and the environment.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 287
#82 Mandeville Parks and Recreation Master Plan: Designing for a Changing Climate
The Mandeville Parks and Recreation Master Plan was a culmination of previous planning efforts. First, LA SAFE, a regional study of risk and opportunities, inspired the City of Mandeville’s Flood Resilience Strategy, which focused on framing physical land and water issues. A decade later, the City developed a Parks and Recreation Master Plan that brings creative solutions to today’s most pressing climate-related issues to a local site through collective community-driven projects.
This parks master plan seeks to enhance Mandeville’s identity as a place of natural beauty by prioritizing a nature-based approach to park design and maintenance while increasing multimodal connectivity throughout the city to improve safe and equitable access to parks. The Plan identified three new parks, with a common thread of enhancing the city’s resiliency. The Landfill Site, located on a former city dump adjacent to Tammany Trace Trail, will serve the surrounding community with a planted native meadow, natural playground, and bridge to the Trace. The Carroll Street site seeks to restore the natural flow of a historic bayou to reduce flooding. The 12X site, located west of the North Causeway Toll Plaza will host a pilot living shoreline to protect the eroding banks of Lake Pontchartrain, complete with marsh creation and habitat restoration.
With help from federal funding from a Land and Water Conservation Fund grant, these three parks are in the early stages of design and are funded through various phases of design and construction.
Moderator: Cassie Nichols – Waggonner & Ball
Panelists:
• Cara Bartholomew – Dept. of Planning & Development City of Mandeville
• Clay Madden – Mayor City of Mandeville
• Delaney McGuinnes – Waggonner & Ball
• John Kleinschmidt- Waggonner & Ball
Organizer: Cassie Nichols – Waggonner & Ball
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 291
#83 Advancing Excellence in Federal Permitting Processes
In 2015, Congress passed the Fixing America’s Surface Transportation Act and, under Title 41 (FAST-41), charged the Permitting Council with bringing government agencies together to coordinate environmental reviews and permitting activities, discuss review challenges, and share best practices. This session will kick off with a presentation on FAST-41 and how it can benefit the efficiency and quality of the environmental review and authorization process for covered projects. The presentation will draw on real-world examples of FAST-41 in action, such as the Mid-Barataria Sediment Diversion project, demonstrating covered projects have benefited from FAST-41 coverage through more coordinated, transparent, and efficient environmental reviews and authorizations. The session will also include a moderated panel that will bring together permitting experts from Permitting Council agencies to present lessons learned related to permitting infrastructure in the United States. Panelists will speak to how these lessons can be incorporated for other infrastructure projects and will discuss federal environmental reviews and authorizations, interaction and dependency with state and local authorizations, and how coordination is essential for project management and infrastructure development success.
Panelists:
• Jennifer Mallard – Permitting Council
• Manisha Patel – Permitting Council
Organizer: Kimberly Higgins – US Department of Transportation
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 292
#84 Coastal Carbon Session 2 of 3: Coastal Carbon Upscaling and Accounting
Blue carbon sequestration and storage has moved from a topic of academic study, to an important wetland conservation and restoration approach to store carbon. Whether implemented through individual carbon credit projects or through state/national accounting, current methodologies require the upscaling of site measurements of carbon stocks and fluxes, with important uncertainties inherent in these processes and their estimation. Carbon accounting faces several challenges relating to spatial variability in ecosystem carbon stocks and fluxes across coastal Louisiana, and uncertainties that are propagated through current carbon accounting methodologies. This session will focus on the challenges of translating site-scale carbon measurements into landscape assessments required for carbon accounting. Using examples from Louisiana, it will present approaches to upscaling soil carbon stocks and accumulation, and models to account for changes in carbon stocks and fluxes with land cover change. It will further address uncertainties in net carbon flux estimates, and common coastal carbon accounting issues in project development. Sharing knowledge on challenges and opportunities to upscaling and carbon accounting will ensure we learn from past experiences in Louisiana to improve future coastal carbon accounting and project development.
Moderator: Havalend Steinmuller – Louisiana Universities Marine Consortium
Presenters:
• Andre Rovai – Smithsonian Environmental Research Center
• Skylar Liner – Coastal Protection and Restoration Authority
• Shawn Doyle – The Water Institute
• Rob Lane – Comite Resources
Organizer: Dan Friess – Tulane University
Patterns of marsh surface accretion and carbon sequestration rates across the Mississippi River Delta’s active and inactive coastal deltaic floodplains
Andre Rovai – Smithsonian Environmental Research Center
Wetland expansion occurs in active deltaic coastal basins that are connected to riverine sedimentation. In contrast, wetland degradation occurs in inactive deltaic coastal basins where river engineering strategies associated with flood control restrict river connectivity. Here, we investigated marsh accretion and soil organic carbon (SOC) sequestration rates spanning fresh to brackish to saline zones between active and inactive coastal deltaic floodplains of the Mississippi River Delta (MRD). Short-term marsh surface accretion rates ranged from 1.24 ± 0.35 cm yr−1 in the freshwater marsh to 2.94 ± 0.51 cm yr−1 in the saline marsh in the inactive coastal basin compared to an opposite trend in the active coastal basin with a low vertical accretion rate in the saline site at 1.12 ± 0.17 cm yr−1 and higher accretion values at the freshwater site (2.14 ± 0.49 cm yr−1). Across basins, SOC accumulation rates were similar for both freshwater and brackish sites but higher at the saline site in the inactive basin. Soil organic and inorganic mass accumulation rates, root mass and turnover ratios, and lignin and cellulose content were used to parametrize a soil cohort, the Numerical Understanding of Marsh Accretion Rates (NUMAR) model, that predicts multi-decadal SOC sequestration rates. NUMAR predictions matched site-specific SOC sequestration rates estimated with 137Cs dated soil profiles from brackish and saline marshes for both active and inactive deltaic coastal basins. NUMAR proved efficient to predict SOC sequestration across diverse coastal geomorphic settings and salinity zones in the MRD.
Assessing the impact of the Louisiana Coastal Master Plan on coastal wetland carbon sequestration using the Land Use Carbon Simulator
Skylar Liner – CPRA | View Presentation
Ecosystem- and landscape-level assessments of carbon sequestration are increasingly required by decision makers to inform land management and climate mitigation policies. The objective of this project is to develop scenario-based forecasts that will inform Louisiana’s climate mitigation strategy to achieve net zero greenhouse gas emissions by 2050. Because coastal wetland ecosystems can effectively sequester carbon, land management that enhances wetland carbon sequestration has been increasingly recognized as a viable solution for climate mitigation. Scenarios that focus on carbon sequestration in coastal wetlands, such as the Louisiana Coastal Master Plan, will play an important role in the State’s climate action strategy. Therefore, the ability to quantify historic, current, and future carbon sequestration in coastal ecosystems is critical to developing an accurate and effective mitigation plan for Louisiana. To assess the impact of land management on coastal wetland carbon, we developed a decision-support tool, the Land Use Carbon Simulator (LUCAS), which integrates landscape change and carbon cycling sub-models to project historic and future estimates of carbon sequestration with uncertainty. This presentation highlights recent advances in the LUCAS model to incorporate critical wetland-specific carbon fluxes, including soil carbon accumulation and lateral flux of dissolved carbon, that have been developed and validated using field data from 24 sites across the Mississippi River Deltaic Plain. We present restoration scenarios from the Louisiana Coastal Master Plan, highlighting the importance of wetland carbon fluxes to overall ecosystem- and landscape-level carbon assessments, and illustrate how these spatially-explicit projections can be used to inform climate mitigation strategies in Louisiana.
Quantifying spatial and temporal uncertainty in Louisiana’s coastal carbon
Shawn Doyle – The Water Institute | View Presentation
The Louisiana coastal ecosystem is a critical carbon sink, but its future net carbon flux is uncertain due to various factors including land loss, response of plant communities, and methane emissions. To better understand the drivers of uncertainty and inform management decisions, we conducted an eFAST sensitivity analysis to identify the most influential parameters and assumptions affecting net carbon flux estimates.
Our analysis examined uncertainties across multiple spatial and temporal scales, considering factors such as soil carbon loss from marsh collapse, methane emissions, and changes in plant productivity. We found that the relative importance of these uncertainties varies spatially and temporally. For instance, uncertainties related to land loss are particularly significant in areas prone to marsh collapse, while methane flux uncertainty becomes more influential in fresher and intermediate salinity regions. Moreover, the time horizon considered impacts the overall uncertainty, with longer time scales projecting greater land loss and associated carbon implications.
By quantifying the contribution of individual uncertainties to the overall uncertainty in net carbon flux, our study provides valuable insights for policymakers and researchers seeking to develop effective strategies for mitigating climate change and protecting coastal ecosystems.
Common mistakes in carbon accounting and pitfalls to obtaining blue carbon credits for coastal restoration
Rob Lane – Comite Resources | View Presentation
Carbon accounting for coastal restoration projects is frequently based on extrapolations from literature rather than site-specific data, which can lead to inaccurate estimates of carbon sequestration potential. A common mistake is neglecting to adjust for baseline conditions when calculating additionality, the net carbon benefits of a project. Additionally, ephemeral plant species like Spartina spp. should not be incorporated into long-term carbon storage calculations since they do not contribute meaningfully to stable carbon stocks. Double counting, particularly by using both root-shoot ratios and soil carbon productivity data, leads to overstatements of a project’s potential to generate carbon credits. Furthermore, failure to account for the decomposition of organic matter, which may release stored carbon back into the atmosphere, can exacerbate these inaccuracies. Securing blue carbon credits for coastal restoration poses several significant challenges. One hurdle is meeting additionality requirements, which mandate that a project must not be financially viable without carbon financing, limiting the eligibility of projects with other funding streams. Strict start-date rules, requiring that carbon monitoring begins within three years of project initiation, often conflict with the realities of long-term restoration projects, delaying or disqualifying them from credit eligibility. Statistical confidence requirements are difficult to meet without increasing the number of sampling plots, adding to the cost and logistical complexity of the project. Moreover, the high variability of greenhouse gas emissions, particularly methane (CH4) and nitrous oxide (N2O), from wetland ecosystems complicates the ability to meet market standards for carbon accounting, as these emissions can offset the sequestration benefits.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 290
#85 A “fish eye’s” view of wetland loss and restoration in Louisiana: addressing gaps in the science to maximize benefits to fisheries productivity
Louisiana is renowned for its commercial and recreational fisheries. The extraordinary fisheries productivity of the wetlands surrounding the Mississippi River was recognized by the Gulf of Mexico’s early researchers, with Gordon Gunter deeming the area “The Fertile Fisheries Crescent” in 1963. This area has since experienced compounding disasters including ongoing wetland loss, hurricanes, and Deepwater Horizon. These issues in Louisiana have been the focus of intense scientific investigation because State, Federal, and non-governmental partners have long recognized the importance of these resources to the local and national economy. These researchers and coastal managers left a legacy of work that helps us understand the processes driving change in our wetlands; however, we are still uncertain how fisheries and estuarine food webs are affected by wetland loss and coastal restoration. Legal settlements resulting from the Deepwater Horizon Oil Spill have provided funds to enable Louisiana’s coastal managers to answer these questions. Large-scale monitoring efforts are now underway to build on past work and understand how coastal fishes and crustaceans, and the lower trophic levels they rely upon, respond to restoration and coastal change. In this session, we will explore the issues facing Louisiana’s coastal fisheries and discuss ongoing efforts to answer questions that coastal managers and fisheries scientists have pondered for decades.
Moderator: Erin Kiskaddon – The Water Institute
Panelists:
• Chris Macaluso – Theodore Roosevelt Conservation Partnership
• Erin Kiskaddon – The Water Institute
• Emelia Marshall – The Water Institute
• Shaye Sable – Dynamic Solutions, LLC
Organizer: Haley Gentry – Tulane Institute on Water Resources Law & Policy
Perspectives on wetland loss and fisheries in Louisiana
Chris Macaluso – Theodore Roosevelt Conservation Partnership
Wetland loss has had a profound effect on the productivity of Louisiana’s coastal estuaries as well as limiting the ability of anglers to access productive fishing areas. The loss of brackish and freshwater coastal marshes, especially in the Barataria, Timbalier and Terrebonne Basins, is having a noticeable negative effect on redfish, speckled trout and other coastal fisheries production and production of vital forage species. Redfish and speckled trout rely on the marsh edges, ponds, submerged vegetation and narrow bayous and trenasses that are the characteristic of healthy estuarine wetlands, the exact kinds of habitats that have experienced extensive loss in the last 50-plus years due to subsidence and erosion. While Louisiana has historically been the most productive state for redfish, speckled trout, black drum, flounder and other estuarine-dependent species due to the extensive wetlands of the Mississippi River Delta, there is evidence from stock assessments and anecdotal accounts from recreational anglers that production has waned over the last three decades. Macaluso will share his perspective on how marsh loss has affected recreational fishing and how areas connected to the Mississippi and Atchafalaya Rivers differ from areas isolated and disconnected from interaction with those rivers in habitat quality, forage base and access.
Implementing lower trophic level baseline data collection to support ecosystem restoration in Barataria Estuary, LA
Erin Kiskaddon – The Water Institute | View Presentation
The Barataria estuary is an ecologically diverse and biologically active region that sustains important commercial and recreational fisheries and coastal communities in southern Louisiana. This location has long been a focus of coastal restoration to counter land loss caused by a variety of natural and manmade changes to Barataria Basin. Monitoring efforts are being planned to assess restoration stemming from the 2010 Deepwater Horizon oil spill including the significant crude oil exposure and response activity impacts. Assessment of ecosystem-scale effects of restoration activities in the Barataria Estuary is poised to be significantly improved by establishing a comprehensive, baseline knowledge of local lower trophic level organisms as well as their population dynamics. Phytoplankton, zooplankton, microphytobenthos, and macroinfauna serve critical roles in sustaining higher trophic levels, including commercially and recreationally valuable fisheries species. This presentation outlines a collaborative effort to implement a three-year field campaign to characterize the current state of lower trophic level communities and food web connectivity in the Barataria estuary. This presentation will highlight the data collection efforts that include visiting 10 stations across the estuary for the next three years and will outline how new data will be used to support the evaluation of ecosystem-wide food-web effects of restoration within the Barataria estuary.
Assessing fish and water column invertebrate abundances in natural and restored marshes across Barataria and Terrebonne Basins to develop reference ranges and restoration target values
Emelia Marshall – The Water Institute | View Presentation
The unprecedented spatiotemporal impacts on natural resources due to the Deepwater Horizon oil spill led to an equally unprecedented restoration plan that aims to restore for the ecosystem-level injury across a number of natural resource types. This restoration plan recognized that habitat restoration not only directly addresses habitat injuries, but also serves as a means to indirectly restore for the fishes and water column invertebrates, or nekton, injured during the spill. Assessing these coastal habitat restoration benefits requires reference ranges – ‘typical’ nekton abundance ranges relative environmental conditions and reflective of ‘baseline’ conditions – and restoration targets – nekton abundances associated with restored habitats accounting for relative habitat maturation state and environmental conditions. The Louisiana Trustee Implementation Group recognized current understanding wasn’t sufficient to develop reference and restoration values for restoration assessment. Thus, a Monitoring and Adaptive Management (MAM) activity was developed to address this knowledge gap. This MAM project consists of three primary tasks: 1) evaluate existing Louisiana fisheries-independent monitoring data for development of reference ranges and restoration targets, 2) develop and implement a monitoring plan to quantify nekton densities in restored marshes using fixed-area sampling gear, and 3) develop reference ranges and restoration target values from these data sources. This presentation will detail the project framework and actions to date, including: a brief discussion of fisheries-independent monitoring analyses conducted thus far; plans for a seasonal, 3-year fixed-area monitoring effort; and finally an overview of the future actions the project will take to develop reference ranges and restoration targets.
Opportunities to Improve Ecosystem Models to Understand How Restoration Impacts Ecological and Fisheries Species Productivity
Shaye Sable – Dynamic Solutions, LLC
The Comprehensive Aquatic Systems Model (CASM) and the Ecopath with Ecosim (EwE) model have been used independently, and as a dual food web model approach, for evaluating key species biomass responses and ecosystem indicators related to food web structure and functioning in relation to several water resource and coastal restoration projects in Louisiana. The existing models have used the best available data for defining species-habitat relationships, initializing species biomasses and growth parameters, structuring the food web and predator-prey interactions, calibration and validation of the model results using fisheries-independent monitoring data from LDWF. However, these models also identified data gaps in our understanding of water quality and lower trophic level (LTL) dynamics in the estuaries – these gaps are in both the modeling and monitoring of the estuaries, in between the hydrodynamics and the fish. There are two primary objectives in using the CASM and EwE models in conjunction with the NOAA-led LTL and Nekton monitoring studies. One goal is to further define and verify key estuarine physical-chemical conditions as they drive primary production and the predominant LTL taxa dynamics. The second goal is to further define and verify how habitat structure affects LTL taxa and key estuarine fish and shellfish species in the estuaries. Improvements to the ecosystem models will support better understanding and representation of existing conditions, and better prediction of responses to restoration and adaptive management actions.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 289
#86 Compound Flood and Coastal Modeling
Coastal areas in Louisiana face heightened flood risks from the interaction of fluvial, pluvial, and coastal hydrodynamics, a phenomenon known as coastal compound flooding. This hazard often exceeds the risks predicted by single-mechanism models, presenting both greater threats to vulnerable regions and significant analytical challenges. Recent advancements in response-based probabilistic modeling, combined with optimized and validated hydraulic frameworks, have made strides in addressing these complexities. This session will explore innovative compound and coastal flood modeling approaches, focusing on the multivariate probability distributions of key flood drivers such as antecedent soil moisture, rainfall, and coastal dynamics, and their integration into hydraulic simulations. Additionally, the session will examine the challenges of flood risk management in Louisiana and beyond under changing climate and storm patterns, emphasizing projections of future risks and the evolving dynamics of compound flooding driven by storm surge, riverine flows, and extreme precipitation.
Moderator: Mark Bartlett – The Water Institute
Presenters:
• Ryan Clark – Halff
• Robert Nairn – Baird
• Agnimitro Chakrabarti – Olsson
Compound Flood Assessment Using an Extended Joint Probability Method with Optimal Sampling
Mark Bartlett – The Water Institute
In support of the Louisiana Watershed Initiative (LWI), the Institute conducted a pilot study of a response-based probabilistic compound flood modeling framework that creates Annual Exceedance Probability (AEP) surfaces of compound flood hazards. This framework was developed as an extension of the joint probability method (JPM) but can also be used to extend the Probabilistic Coastal Hazard Analysis system developed by the US Army Corps of Engineers (USACE). This framework characterizes the multivariate distribution of compound flood drivers and boundary conditions and provides specific guidance in how to map realizations of that distribution to the setup of coupled 2D hydraulic models to realistically capture the hydrodynamics of plausible compound flood events while assigning them appropriate probability weights. To reduce the set of required simulations in probabilistic compound flood modeling to a tractable number of events, the Institute has developed an optimal sampling method which requires fewer assumptions and can be used where closed-form distributions are unavailable, e.g., where distributions are expressed via Monte Carlo samples. This approach involves k-means clustering. This optimal sampling method allows for detailed hazard characterization in cases where simulation runtimes or storage costs would otherwise be prohibitive. Results of a pilot application of this framework will be presented as applied to the Amite River Basin in coastal Louisiana. Finally, we will provide an overview of additional collaborative compound flood risk modeling studies ongoing at the Institute along the Atlantic Coastline and the Gulf of Mexico including along the Texas coastline.
Overview of compound flood modeling for the Lower Rio Grande Valley region of the Texas River Basin Flood Study
Ryan Clark – Halff | View Presentation
In September 2020, the Texas General Land Office (GLO) launched the Combined River Basin Flood Studies in the 49 counties which received a presidential disaster declaration after Hurricane Harvey plus 4 counties in the Lower Rio Grande Valley that received a presidential declaration for flooding in 2015. These studies inform flood risk information to help protect Texans from future floods.
These studies promote sound short- and long-term recovery by increasing the resiliency of communities most at risk of flooding and enabling them to undertake the most effective projects that reflect local priorities and needs. By partnering with active federal and state efforts, these studies seek to draw from the strengths, expertise, and capabilities of public, private, and academic centers of excellence throughout the State of Texas.
In the Lower Laguna Madre region of Coastal Texas, a bivariate analysis was performed using rainfall and surge data to determine dependency. Post-determination of a positive correlation between rainfall and surge during tropical cyclone events, a Copula was developed to generate rainfall-surge pairs to provide boundary conditions to a detailed 2D HEC-RAS model. The RAS model uses a rain-on-mesh approach with 2D infiltration and uses the shallow water equations to model 2D unsteady flow. The choice of the shallow water equations within the RAS model is dictated by the relatively flat terrain of the Lower Rio Grande Valley. Results provide quantitative estimates of compound flooding hazard in the Laguna Vista and Laguna Heights communities of Cameron County, Texas.
Integrating Climate Change Projections and Hydro-Dynamic Wave Modeling for Present and Future Compound Flood Risk
Robert Nairn – Baird | View Presentation
As climate change progresses, the likelihood and complexity of compound flooding events—where storm surge, riverine, and precipitation-driven waters converge—are expected to increase (Garzon et.al., 2016). These events pose significant risks to coastal regions worldwide. Traditional flood risk assessments often fall short in capturing the multifaceted nature of such events, leading to potential underestimation of risks. Recognizing this gap, our study aims to present a generalized approach for simulating future climate scenarios that incorporate the intricacies of compound flooding, alongside other critical variables.
This presentation discusses the numerical modeling application of a future coastal compound flood risk study conducted in Chesapeake Bay, VA USA. In this study, we apply a generalized framework for simulating compound flood events under 4 global climate model results (i.e., CNRM, NORESM, HADGEM, MPI), for two future climate scenarios (i.e., SSP126, SSP585) and for two time horizons (i.e., Mid and Late 21st century). Using our methodology, we created approximately 15,000 synthetic Tropical Cyclones (TCs) and 6,000 Extra Tropical Cyclones (ETCs) representing both existing and future storms influenced by climate change. The developed TCs represents a 7,000-year period for each experiment whereas for ETCs the focus was on quantifying any systematic changes to track and intensity given the last 44 years (1979-2022) of historical ETCs due to increased temperatures and wetter climate states.
Numerical Modeling of Hurricane Storm Surge and Waves with Delft3D FM: A reverse surge problem and modeling solution for Engineering and Design
Agnimitro Chakrabarti – Olsson
The work being presented here considers diverse aspects of the science of flood risk reduction and is directly related to South Louisiana with possible application at other locations as well. The following lists a few key points that defines this interdisciplinary work and incorporates aspects of coastal engineering, climate science and numerical modeling in delivering a solution for LA’s changing coast:
1. The modeling and associated engineering and design presents a methodology for designing resilient and economic flood gates that are able to withstand both regular and reverse hurricane surge.
2. This work relates directly to the hurricane surge induced flooding risk reduction for portions of St. Charles, St. John the Baptist, St. James, Ascension, Assumption, and Lafourche Parishes that are especially vulnerable to catastrophic flooding being in North Barataria.
3. The work compliments USACE Engineering Research and Development Center’s modeling and design of the Upper Barataria Risk Reduction system by incorporating a solution for reverse surge problems for Louisiana floodgates.
4. The modeling considers effects of future land use land cover changes as it incorporates the LAVEG modeling results from the LA Coastal Master Plan. Vegetation induced accretion as well as subsidence is included in the modeling.
5. The modeling considers multiple USACE Eustatic Sea Level Rise scenarios and their effect on design parameters. Hurricane and antecedent rainfall conditions are considered in this modeling and is an improvement of the existing modeling platform.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 288
#87 Coupled Natural and Human Coastal Systems in a Changing World – A MissDelta Session
Many coastal zones and large deltas are under the threats imparted by declining sediment supply, global sea level rise, coastal subsidence, and human engineering. This lightning session seeks contributions on the studies of both natural and social sciences. We propose to gather a series of short presentations that either review past coastal and deltaic studies or highlight recent findings on various aspects of coupled natural-human systems that identify or reduce risk from the coastal and deltaic threats. Topics include, but are not limited to, sediment transport, geomorphology, hydrological alteration, land use change, coastal land loss, hurricanes and floodings, storm intensity, and coastal hazards. Studies may derive from field observations, laboratory experiments, and model (numerical, statistical, machine learning etc.) research across a range of timescales. The session should be of interest to coastal and deltaic scientists, engineers, stakeholders, resource managers and decision makers. The work is supported, in part, by the Mississippi River Delta Transition Initiative (MissDelta) of the National Academies Gulf Research Program; this initiative seeks to explore the geomorphic and human future of the Birdsfoot Delta of the Mississippi and surrounding region, and to expand the diversity of the coastal scholar community.
Moderator:
Monica Burr – Alcorn University
Kehui Xu – Louisiana State University
Presenters:
• Robert Collins – Dillard University
• Thomas Wahl – University of Central Florida
• Sara Santamaria-Aguila – University of Central Florida
• Qiang Sun – Tulane University
• Adam Gartelman – Louisiana State University
• Janaka Wijayawardhana – Xavier University
• Rongqing Du – Louisiana State University
• Mead Allison – Tulane University
• Matthew Hiatt – Louisiana State University
• Carol Wilson – Louisiana State University
Organizer: Kehui Xu – Louisiana State University
A time-series current-trend forecast of economic loss in the Bird’s Foot Delta
Robert Collins – Dillard University | View Presentation
The loss of land and population in the Bird’s Foot Delta results in the loss of jobs in the region and the loss of tax revenue for the entire state. This study uses a time-series current-trend model, applied with IMPLAN economic impact and modeling software, to forecast job loss and tax revenue loss in the state, in a series of 5 year intervals, if there is no public policy intervention to stop the current trends in the Bird’s Foot Delta.
Probabilities and trends of extreme storm surges along the northern Gulf of Mexico coast
Thomas Wahl – University of Central Florida
Obtaining robust and spatially continuous estimates of storm surge and extreme water level return periods for coastal flood risk assessments and adaptation planning remains a challenge. These return periods may also be non-stationary due to changes in storminess as a result of global warming and natural climate variability. Here we produce and analyze a new dataset of storm surge and extreme water level return periods using a Bayesian Hierarchical Model (BHM) that leverages spatial dependences in storm surge data to enable sharing of information across space. The BHM produces more robust return level estimates with associated uncertainties at tide gauges compared to the traditional at-site approach, while also providing the same information at ungauged locations. From the Bayesian estimates, we infer spatial patterns of return levels along the northern Gulf of Mexico coastline. The BHM also considers a non-stationary location parameter allowing us to identify regionally coherent long-term trends in extreme storm surges. Overall, the results indicate that contemporary and future coastal risk assessments may underestimate the flood hazard component with potential implications for misguided design and adaptation planning.
Can the 100-year event produce the 100-year flood?
Sara Santamaria-Aguila – University of Central Florida |View Presentation
Assessing flooding from compound events is crucial for effective decision-making because these events can worsen flood impacts compared to single-driver scenarios and may require different adaptation strategies. Currently, there is no standardized method for evaluating compound flood hazards. Two primary methods are used: the event-based approach and the response-based approach. The more common event-based approach assumes that the likelihood of flooding is equivalent to the probability of the event occurring. However, actual flooding is influenced by various factors, including topography and water dynamics. The response-based approach involves simulating thousands of events and provides a more accurate flood hazard characterization at household level, but is computationally intensive and less frequently employed. Flood hazard maps produced based on these two approaches can inform different decision makers. For example, flood hazard maps based on specific events are more useful than response-based maps for emergency management and municipal finances, who need to respond to specific events. However, household flood risks are more accurately characterized based on the empirical distribution of water depths at household levels. Here, we present results and lessons learned from the compound flood analyses performed for the Northeast US with intense stakeholder engagement as a part of the Megalopolitan Coastal Transformation Hub. The framework can serve as a blueprint to similar studies in other coastal regions prone to compound flooding such as the coast of Louisiana.
Causes of accelerated High-Tide Flooding in the U.S. since 1950
Qiang Sun – Tulane University
The U.S. coastlines have experienced rapid increases in occurrences of High Tide Flooding (HTF) during recent decades. While it is generally accepted that relative mean sea level (RMSL) rise is the dominant cause for this, an attribution to individual components is still lacking. Here, we use local sea-level budgets to attribute past changes in HTF days to RMSL and its individual contributions. We find that while RMSL rise generally explains > 84% of long-term increases in HTF days locally, spatial patterns in HTF changes also depend on differences in flooding thresholds and water level characteristics. Vertical land motion dominates long-term increases in HTF, particularly in the northeast, while sterodynamic sea level (SDSL) is most important elsewhere and on shorter temporal scales. We also show that the recent SDSL acceleration in the Gulf of Mexico has led to an increase of 220% in the frequency of HTF events over the last decade.
Seasonal variations of infilling sediments in sandy dredge pits on eastern Ship Shoal of coastal Louisiana
Adam Gartelman – Louisiana State University | View Presentation
Sediment has been dredged in many coastal zones for restoration projects such as barrier island restoration and marsh creation around the world. Ship Shoal, a prominent transgressive shoal situated in the Northern Gulf of Mexico, has played a vital role in supplying high-quality sands in coastal Louisiana. This natural resource has been particularly valuable for coastal management efforts aimed at enhancing resilience against erosion and storm impacts. The Caminada Dredge Pit was first excavated in 2014, with a follow-up dredging event occurring in 2016. More recently, the Terrebonne Dredge Pit, located approximately 4 kilometers to the west of Caminada Dredge Pit, was developed between 2021 and 2022. This study seeks to compare the sediment characteristics of these two dredge pits, focusing on the differences between a newly established pit and one that has been in use for nearly a decade. To achieve this, we will analyze various parameters, including grain size distribution, organic matter content via loss-on-ignition, and the percentage of carbonate present in the sediments collected in multiple seasons during six research cruises. Additionally, geophysical analysis will be employed to assess the overall morphology of each pit. By understanding these differences, we aim to gain insights into the impacts of dredging practices over time and inform future coastal restoration strategies in the Mississippi River Deltaic Plain.
Photosynthesis of dominant vegetation and soil nutrient profiles in two eastern sites of the Mississippi bird foot delta: A preliminary investigation
Janaka Wijayawardhana – Xavier University
Mississippi bird foot delta is a highly fragile and dynamic ecosystem of immense ecological and economic significance. Although literature is available on the vegetation structure of the delta, the information on in-situ plant function and how it’s affected by soil nutrient profile is limited. We investigated key photosynthetic variables including both gas exchange and photosystem function of Phragmites australis and major soil chemical properties including macro- and micronutrients, in two sites on the eastern side of the bird foot delta, Brant Splay and Bouy Pond. Photosynthetic variables of Colocasia esculenta also were studied in Brant Splay. Stomatal conductance of both species in Brant Splay, and P. australis in Bouy Pond averaged >0.3 mol m-2 s-1. Stomatal conductance and transpiration rate of P. australis appear to be greater in Brant Splay than Bouy Pond. Quantum yield of Photosystem II was >0.5 in both species at a given site. Total salt content was 360% greater in Bouy Pond than Brant Splay. Organic matter content averaged 4.6% in Brant Splay but only 2.7% in Bouy Pond. Percentages of soil Carbon and Nitrogen also were greater in Brant Splay than Bouy Pond. Brant Splay had greater soil Magnesium but lower Calcium levels. Data collected so far on leaf gas exchange and photosystem function suggest no major environmental stress in the two species in these sites. However, lower stomatal activity in P. australis in Bouy Pond may reflect a degree of salt stress compared with Brant Splay. Soil nutrient profiles show variation between the sites on the easter
A Sediment Transport Model in Galveston Bay during Hurricane Harvey
Rongqing Du – Louisiana State University
Understanding sediment transport dynamics during extreme weather events like hurricanes is critical for predicting coastal morphodynamics and assessing the impacts on ecosystems and human activities. This study develops a sediment transport model focusing Galveston Bay to investigate sediment resuspension, deposition, and distribution under the influence of Hurricane Harvey. The model, built in the Regional Ocean Modeling System (ROMS), integrates high-resolution (100-m) sediment transport processes, focusing on how wind, precipitation, river discharge, and tidal forces drive sediment transport pathways. The sediment model uses detailed seabed data from the Texas Sediment Geodatabase (TxSed), which provides a comprehensive dataset on sediment grain size, type, and distribution. Major inputs and calibration data include river discharge data from the US Geological Survey (USGS) and hydrological data from the WRF-Hydro model. By analyzing sediment fluxes through bay inlets, navigational channels, and shallow water, this study will quantify sediment sources, sinks, and changes in seabed morphology during and after the hurricane. The model also aims to compare sediment contributions from multiple riverine sources and track how fine and coarse sediments behave differently in terms of deposition and transport. This enhanced understanding of sediment dynamics will contribute to better coastal management, particularly concerning sediment accumulation in navigation channels, water quality issues, and habitat preservation in the face of increasingly frequent storms.
The Future of the Birdsfoot Delta Region: Overview of the Mississippi River Delta Transition Initiative (MissDelta)
Mead Allison – Tulane University | View Presentation
The lower Mississippi River Delta (a.k.a. Birdsfoot Delta) is an iconic promontory that provides navigation access to North America and is home to numerous communities, extensive energy and transport infrastructure, valuable commercial and recreational fisheries, federal wildlife preserves, and broad fluvial, wetland, estuarine, and marine ecosystems of the Northern Gulf of Mexico. Recent research shows that the Birdsfoot Delta is beginning to disappear both above and below sea level. Despite a century of scientific study of the Birdsfoot region, great uncertainty exists regarding its future sustainability under increasingly intense environmental change, modification of the river channel for navigation, and increasing energy costs for maintenance. The MissDelta Consortium is a 14 institution, 38 PI, five-year effort funded by the National Academies Gulf Research Program. Our goal is to address major questions including what is the most likely future trajectory of the Birdsfoot? Does that trajectory involve total collapse? What form would collapse take, and at what rate? What are the implications for the immediate region and surrounding coastal areas, both ecologically and socio-economically? And how do we educate a new generation of scholars to address these issues that reflects the diversity of the regional population? The consortium is striving to address these questions through co-development of a research program with a diverse group of stakeholders that span federal and state agencies to parish governments to NGOs, industry, and community organizations.
Importance of channel-floodplain interaction for river delta resiliency: Lessons and opportunities in the Mississippi River Delta
Matthew Hiatt – Louisiana State University
Hydrological connectivity is a framework for assessing water-mediated transport between landscape elements. In river deltas, connectivity between distributary channels and deltaic floodplain wetlands is modulated by levees, crevasse formation, the river hydrograph, vegetation, marine and meteorological forcings, and morphological change, among others. Maintenance of channel-floodplain interaction is vital for mineral sediment delivery and organic accretion, both important factors in mitigating losses due to relative sea level rise. This presentation will focus on current challenges and efforts in quantifying channel-floodplain connectivity with an emphasis on activities in the Mississippi River Delta (MRD) through the MissDelta Project. Observational efforts including dye propagation studies and hydrographic surveying in the MRD paired with numerical modeling efforts will be discussed. Connectivity dynamics across temporal and spatial scales are important drivers for predictive modeling efforts in the MRD.
A modern assessment of wetland geomorphology in the lower Balize delta, Mississippi River
Carol Wilson – Louisiana State University
Geologically speaking, the Balize delta lobe of the Mississippi is very young. While other delta lobes like the St Bernard and the LaFourche were building vast deposits ~4000 and ~1700 years ago, respectively, the Balize delta lobe has only been building off the southeastern-most edge of the delta for the past ~500 years. Since 1839, several different subdelta lobes developed in the region (e.g. Cubits Gap and Garden Island Bay), but high rates of relative sea-revel rise compared to sediment supply has deteriorated the delta topset in recent decades. Several man-made crevasses have been constructed over the past 40 years to increase intertidal vegetated land areas. This talk will highlight the successes—and occasional failures—of these mitigation projects and preliminary data from the MissDelta Project on how the man-made crevasses compare to natural crevasses in the lower delta. We will also discuss how a recent die-off of Phragmites australis (common reed) in the lower delta has highlighted the need to improve the understanding of abiotic thresholds, species-specific tolerances, and eco-geomorphic consequences of vegetation loss and species shifts.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 285
#88 Soaking It In: Designing Flood-Resilient Communities
This session explores integrated strategies for urban resilience and flood management in New Orleans. Presenters will highlight projects that combine green, blue, and grey infrastructure to reduce flooding while enhancing community spaces. The St. Bernard Neighborhood redevelopment and Gretna City Park showcase how stormwater detention and landscape design can improve flood resilience and public amenities. A broader look at New Orleans’ flood strategies will examine how nature-based solutions reduce reliance on pumps, while a review of past resilience projects will assess their effectiveness. Together, these discussions offer insights into creating more adaptable, water-conscious communities.
Moderator: Kevin Wilkins – Trepwise
Presenters:
• Thomas Cancienne – Stantec
• Monica Stochl – Jacobs
• Meagan Williams – City of New Orleans Office of Resilience and Sustainability
• Andy Sternad – Waggonner & Ball
• Sean Fowler – Tulane School of Architecture
Gentilly Resilience District St. Bernard Neighborhood – Integrated Green Infrastructure, Stormwater and Recreational Needs
Thomas Cancienne – Stantec | View Presentation
The City of New Orleans completed the design and is preparing to break ground in the St. Bernard Campus area as part of Gentilly’s National Disaster Resilience (NDR) Program.
The St. Bernard Neighborhood Campus project is to improve neighborhood drainage, add green infrastructure and park elements, and rebuild the New Orleans Recreation Development Commission’s (NORDC) Willie Hall Playground facilities. Pre-Katrina, the Willie Hall Playground and athletic fields were the home to decades of neighborhood youth sports teams and activities. This project marks the long-awaited return of Willie Hall Playground to the St. Bernard neighborhood.
In addition, this project will serve the enhanced purpose of reducing flooding by storing up to 5 million gallons of stormwater in underground detention basins. This will be the largest underground stormwater detention basin in the region. Educational water features will be placed along walking trails/paths that meander throughout the project limits. These installations will raise awareness of water’s role in the New Orleans urban environment.
Beyond Pumps: Blending Blue, Green, and Grey Infrastructure to Reduce Flooding and Optimize Resilience in New Orleans
Monica Stochl – Jacobs
Meagan Williams – City of New Orleans Office of Resilience and Sustainability
Flooding remains a critical issue in Greater New Orleans, particularly as overwhelmed drainage pump stations (DPS) face increasing strain. This project adopts a comprehensive hydrologic and hydraulic (H&H) approach to prioritize a suite of projects that blend blue, green, and grey infrastructure. By strategically integrating nature-based and traditional solutions, we aim to reduce flood risk without overburdening the city’s vital pump systems.
New Orleans’ unique geography and climate make it particularly vulnerable to flooding. The city’s reliance on DPS to manage stormwater is becoming less sustainable due to aging infrastructure and the growing intensity of storm events. Traditional grey infrastructure, while effective, often fails to address the root causes of flooding and can be costly to maintain. In contrast, blue and green infrastructure solutions offer sustainable, cost-effective alternatives that enhance the city’s resilience to flooding.
This project will employ advanced H&H modeling techniques to assess flood risks and identify priority areas for intervention. By integrating nature-based solutions, urban green spaces with traditional infrastructure upgrades, we aim to create a balanced and sustainable flood management system. This approach will reduce pressure on DPS, enhance system redundancy and reliability, and optimize maintenance and operations.
Through strategic investments and stakeholder collaboration, we can reduce flood risk, improve system efficiency, and ensure the long-term sustainability of New Orleans’ flood management infrastructure.
People & Place: The Water & Community of Gretna City Park
Andy Sternad – Waggonner & Ball | View Presentation
Gretna City Park is the first completed pilot project of the Louisiana’s Strategic Adaptations for Future Environments (LA SAFE) program, the urban complement to the State’s ambitious Coastal Master Plan. This presentation will take a deep dive into the planning, design, and construction of Gretna City Park, including the stormwater, green infrastructure, and native landscapes that make it a model for regional resilience, and the community amenities making it one of the best urban parks on New Orleans’ West Bank. Beginning with the LA SAFE planning effort, the presentation will situate the park in the context of the coast and the Mississippi River, highlighting its identification early in the planning process as a site for high-impact stormwater storage. The park’s conception in the context of this regional resilience planning form the foundation for a people-centered design process merging green infrastructure with park amenities that deepen the connection between residents, water, and ecology, making it a model for urban parks up and down the Gulf Coast. Careful consideration of existing landscapes and water on the site were merged with thoughtful excavation for additional stormwater retention and habitat regeneration, all with an eye towards shaping great outdoor spaces for neighbors to interact with water. Additional design strategies and projects from the Greater New Orleans Urban Water Plan and LA SAFE will be presented as comparative case studies.
A Drop in the Bucket: A review of the projected performance of proposed New Orleans resilience projects
Sean Fowler – Tulane School of Architecture
New Orleans is a city reclaimed in large part from the swamp. In the three centuries since the high-ground was first settled, ever-grander infrastructures have been developed to manage river flooding, stormwater and drainage. Since the end of the nineteenth century, this has included a regional-scale effort to dewater marshes, swamps and floodplains to “create” new land for agriculture and habitation.
There was a reevaluation of the defensive and infrastructural approach to managing stormwater and draining land starting in the twenty-first century and escalating after Hurricane Katrina devastated the city and the Gulf Coast. This reevaluation led to proposals attempting to redress historic failures and repair New Orleans’ systems, and proposals attempting to completely reshape the city to address both current and future challenges.
This presentation and poster compare the projected and measured (when applicable) performance of selected proposals from the last ten years, both to original designs and to the other projects. This comparison attempts to quantify the impact these projects could or do have on the other systems of the city. A projective or retrospective analysis is valuable for future resilience planning, other municipalities facing similar issues, and can seek to quantify the costs and benefits, economic impacts and ecosystem services provided by these past proposals or projects.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 284
#89 Chandeleur Island Restoration Project (PO-0199) – Ecology of the Islands
The Chandeleur Island Restoration Project is located in St. Bernard Parish, Louisiana within the Breton National Wildlife Refuge. The Project Area is comprised of restoration areas on North Chandeleur and New Harbor Island. The Project sediment borrow area is located at Hewes Point, just to the north of North Chandeleur Island. The purpose of the Project is to engineer and design a restoration project benefitting the Chandeleur Islands with a particular focus on bird and sea turtle habitat, enhancement of submerged aquatic vegetation habitat, and creation/restoration of barrier islands and coastal headlands. Proposed project restoration features include beach/dune/marsh fill, isolated (pocket) marsh construction, back-barrier sand reservoir construction, and the construction of a feeder beach on the Gulf-facing shore of North Chandeleur Island. The construction and monitoring cost of the project is estimated at approximately $350 million. An extensive ecological data collection effort was undertaken to describe the existing habitat conditions, bird nesting and foraging, sea turtle nesting, and mapping the extensive seagrass meadows over the entire 13-mile island. This session will introduce the project and outline the purpose and need, discuss the survey findings for sea turtle nesting, present and illustrate the abundance and diversity of marine seagrass meadows identified during the surveys, and show the diversity and abundance of shorebird nesting and utilization quantified during the surveys.
Moderator: Michael Poff – Coastal Engineering Consultants, Inc.
Presenters:
• Todd Baker – CPRA
• Matt Weigel – Louisiana Department of Wildlife and Fisheries
• Stephanie Healey – SWCA Environmental Consultants
The Chandeleur Islands, a National Treasure in need of Restoration
Todd Baker – CPRA | View Presentation
The Chandeleur Islands are a remote barrier island chain in the northern Gulf of Mexico, located in St. Bernard Parish, Louisiana. These islands make up the second oldest National Wildlife Refuge in the United States, the Breton National Wildlife Refuge. Our conservation president, Theodore Roosevelt, established the National Wildlife Refuge System, and the Chandeleur Islands are the only refuge that he ever visited.
The remoteness of the islands, combined with their vast and diverse seagrass meadows makes them attractive to a wide variety of sea turtles, birds, and fisheries. Each year, the Chandeleur Islands host a unique assemblage of fish and wildlife species, not found elsewhere in the northern Gulf of Mexico. They are home to 79 species identified as “Species of Greatest Conservation Need.” Unfortunately, this coastal wilderness and its habitats are disappearing at an alarming rate. Since 1915, approximately 90% of the islands’ acreage has slipped into the Gulf of Mexico. The impacts of subsidence, erosion, hurricanes, and the 2010 Deepwater Horizon Oil Spill have caused the islands to fragment and shrink over time.
Fortunately, an effort is underway to restore the Chandeleur Islands. Funded by the Regionwide Trustee Implementation Group and the state of Louisiana, the Department of the Interior, CPRA, and Coastal Environmental Consultants are implementing an engineering and design effort to restore the Chandeleur Islands. This effort focuses on restoring specific wildlife habitats and building a project that will increase the islands’ longevity for decades to come.
The State of Sea Turtle Nesting on Chandeleur Island
Matt Weigel – Louisiana Department of Wildlife and Fisheries | View Presentation
Chandeleur Island is Louisiana’s easternmost and largest barrier island. It and surrounding islands (South Chandeleur Island and Freemason Island) are the only Louisiana islands that are known to provide key habitat for nesting sea turtles. However, the islands’ beaches and dunes are sand-starved, and as the island erodes, sea turtle nesting habitat is being lost and rapidly degraded. Fortunately, the Regionwide Trustee Implementation Group has provided funding for Chandeleur Island Restoration engineering and design project. As part of the engineering and design effort, sea turtle nesting surveys were conducted on the Chandeleurs between 2022 and 2024. These surveys documented numerous nesting crawls and nests, as well as successful hatches. Three sea turtle species were found to utilize the islands’ beaches, Loggerhead, Green, and Kemp’s Ridley, the most endangered sea turtle species in the world. Although, prior to 2022 surveys, Louisiana beaches were not known to be significant to the Kemps’s Ridley or other sea turtle species, genetic analysis of nest material is indicating that Chandeleur Island may, in fact, be quite meaningful to the recovery of Kemp’s Ridleys. The ongoing Chandeleur Island Restoration engineering and design effort is focused on restoring nesting habitat for sea turtles. Through the aforementioned surveys, other data collection, and consultation with sea turtle subject matter experts, the design team has defined turtle nesting habitat needs and incorporated those requirements into the planned island restoration design. With restoration, Chandeleur Island is expected to serve as a viable nesting site for important sea turtle species for decades to come.
A deep dive for Chandeleur Islands restoration: Surveying 3,000 acres of unique habitat along Louisiana’s barrier islands
Stephanie Healey – SWCA Environmental Consultants | View Presentation
The Louisiana Coastal Protection and Restoration Authority (CPRA) is leading the engineering and design of a restoration project benefitting submerged aquatic vegetation (SAV) habitats in the Chandeleur Islands and the many species that use them. This project demonstrates how to implement a comprehensive landscape analysis to provide invaluable data to restoration planners: capturing changes in SAV distribution; documenting marsh loss or accretion; and monitoring shoreline and land use changes in the coastal environment. In support of the restoration design and habitat restoration planning goals, SWCA designed and implemented a SAV study plan to understand the seagrass distribution and community composition along the bay side of the main Chandeleur Island, and New Harbor Island, in support of the restoration design and habitat restoration goals for these barrier islands. The SAV survey was conducted during the peak growing season using a rapid assessment approach consisting of a tessellated hexagonal sampling grid with randomized sampling locations where information was collected for species composition and coverage, canopy height, and water quality parameters. Additionally, real-time satellite imagery was acquired and used to map the extent of the seagrass, which was ground truthed through in-water spot checks. Total seagrass cover was digitized using a mixture of photointerpretation and image analysis. Additional analysis used ArcGIS modeling software to estimate the total cover density and species-specific cover density across the study area. The cover model provides supporting details that will aid in understanding the relationship between species distribution and adjacent barrier island structure according to species-specific habitat requirements and limitations. At the main Chandeleur Island, this information is being used to guide restoration design for the island, to understand and try to quantify potential impacts to the existing seagrass resources.
The Birds of Chandeleur Island
Todd Baker – CPRA | View Presentation
The Chandeleur Islands are part of Breton National Wildlife Refuge, established in 1904 by executive order of Theodore Roosevelt. The refuge was created to protect nesting birds as well as wintering waterfowl and shorebirds. In the 1980’s, the Chandeleur Islands were recognized as the world’s largest congregation of nesting colonial waterbirds. However, as the island’s acreage has eroded over time, so have the number of birds utilizing the Chandeleurs.
Bird surveys were conducted on the Chandeleurs between 2022 and 2024, funded by the Regionwide Trustee Implementation Group as part of the Chandeleur Island restoration engineering and design effort. Four surveys were completed, including colonial waterbird surveys, solitary nesting bird surveys, waterfowl surveys, and winter shorebird surveys. These surveys documented 171 bird species utilizing the islands, including 38 species designated as “Species of Greatest Conservation Concern” and two hybrids, including the “Chandeleur Gull.” Significant numbers brown pelicans, red knots, Sandwhich terns, royal terns, reddish egrets, and redhead ducks were observed using the islands.
The Chandeleur Island Restoration engineering and design effort is underway and focused on restoring nesting and foraging habitats for birds. Bird surveys and subject matter experts were consulted to define bird habitats and restoration features in the design. In addition to restoring bird habitats in the short term, features are being designed to preserve current bird nesting habitats and increase the islands’ longevity by several decades.
Thursday, May 22 | 12:30 – 2:00 p.m. | Room 283
#90 Louisiana Coastal Master Plan Modeling: Lessons from Hindcasting and Advances in Risk Modeling (Highlighted Red)
Louisiana’s Coastal Master Plan models are typically used to understand the current and potential future coastal landscape and risks to wetlands and communities. The first three presentations in this session focus on recent efforts to use these models in a novel way—to take a retrospective look at the last 15 to 20 years through hindcasting. They answer questions like: How well do our vegetation model predictions of species distribution align with CRMS observations over the last decade and a half? How have protection projects reduced storm surge-based flood risk since Hurricanes Katrina and Rita? The final presentation focuses on exploration of an innovative method for making surge and wave modeling across varying landscapes more efficient for Coastal Master Plan project evaluation and risk analysis through the use of machine learning-based surrogate models.
Moderator: Jessica Converse – CPRA
Presenters:
• Zhanxian Wang – Moffatt & Nichol
• Madeline Foster-Martinez – University of New Orleans
• Patrick Kane – The Water Institute
• Harry Vorhoff – Plauché & Carr LLP
Organizer: Ashley Cobb – CPRA
CRMS-Era Restoration Hindcast
Zhanxian Wang – Moffatt & Nichol
CPRA’s Integrated Compartment Model (ICM) suite has been developed and improved to support the 2017 and 2023 Coastal Master Plans. The ICM is used to model proposed projects 50 years into the future to determine their effectiveness in achieving restoration and protection goals and to prioritize investments. There is a recent interest in quantifying the ecosystem benefits of the Louisiana coastal restoration program since the formation of CPRA in 2006, which is also when they began collecting CRMS data. To assess the magnitude of project benefits, model simulations developed an alternate history of coastal Louisiana where restoration projects are not implemented. This hindcast focuses on simulating this alternate history, as well as a simulation of actual history with the ICM to assess restoration project ecosystem/landscape benefits during the CRMS era (2006 – present). All large-scale projects constructed from 2006 through 2023 were examined. Those that impact the coastal landscape and coastal hydrology were identified and then removed from the initial landscape developed for the 2023 Coastal Master Plan, and the ICM-Hydro compartment and link attributes were updated to reflect the pre-project conditions. For the “true history” hindcast, these projects were systematically implemented within the ICM in the proper time sequence. The historic hindcast outputs were compared to observational data to validate the model performance. The alternate “no projects” hindcast was compared against the historic hindcast to quantify the direct and cumulative benefits of the coastal restoration program.
ICM-LAVegMod Model Hindcast/Updates
Madeline Foster-Martinez – University of New Orleans
The Louisiana Vegetation Model (LAVegMod) predicts vegetation distributions across coastal Louisiana in response to changing environmental drivers. These distributions in turn determine the rate of organic matter accretion and habitat suitability for species of interest. A hindcast to explore the model performance is now possible thanks to the availability of over 15 years of Coastwide Reference Monitoring System (CRMS) data along with the vegetation maps used as initial conditions for previous Master Plan models. Two sets of hindcast runs were conducted: one with processes driven by ICM-Hydro output, and another with processes driven by CRMS measurements. Each set contained a run from 2010 to 2014 and from 2015 to 2018, giving three points of comparison (one for 2014 and two for 2018). Each species was mapped from the resultant vegetation distribution (i.e., percent cover of each species in every grid cell) and compared to the satellite-derived vegetation maps. Flotant was removed from this analysis since coastwide data was not available for comparison. Instead, an independent version of LAVegMod was run for CRMS stations with substantial flotant coverage. This talk will present results from the hindcasts, as well as describe updates made to the organic matter accretion rates and forested wetland loss mechanisms.
A Coastwide Risk Hindcast from Hurricanes Katrina & Rita to Present Day
Patrick Kane – The Water Institute
The Louisiana Coastal Master Plan team sought to explore how investments made to build land and restore ecosystems, improve structural risk reduction systems, and support flood risk mitigation through nonstructural risk reduction (elevations, buyouts, etc.) have reduced flood risk across Louisiana’s coast since CPRA was created. To accomplish this goal, The Water Institute used landscape hindcasts discussed earlier in this session, in conjunction with a re-creation of the coast’s structural risk reduction features at the time of Hurricanes Katrina and Rita in 2005. The Coastal Louisiana Risk Assessment (CLARA) model was also reconfigured to represent conditions at the time of Katrina to support an analysis reflective of a scenario where structural risk reduction systems would have only been reconstructed as they were rather than improved into systems such as the present Hurricane Storm Damage Risk Reduction System (HSDRRS). Storm surge and waves, flood depths, and flood consequences (damage and exposure) from this “No Investment” condition were compared to estimates from the 2023 Coastal Master Plan, and the differences provide an estimate of the return on investment for risk reduction projects across coastal Louisiana made or supported by CPRA from 2007-2023. This presentation will summarize the scope of the work, analysis methods, and key findings.
A Surrogate Modeling Approach to Scenario Generators for Estimating Future
Mohammad Ahmadi Gharehtoragh – Purdue University
Planners managing complex systems often rely on similarly complex models to inform decision processes. For risk-based decision-making, they may need to simulate a large ensemble of hazardous events over long planning horizons matching the long useful lifetime of infrastructure. Under deep uncertainty about sea level rise, population change and other factors, this problem is further compounded by the need to model risk for many potential futures. Model complexity (i.e., computational costs) therefore constrains planners’ ability to effectively account for uncertainty.
In this talk, we describe progress to date in developing machine learning-based surrogate models to emulate storm surge and wave hydrodynamics much more efficiently and on varied landscapes. By training surrogate models on ADCIRC+SWAN simulations from the 2023 Coastal Master Plan, we can predict inundation from synthetic tropical cyclones (TCs) as a function of not only the TC characteristics, but of landscape features (e.g., topography/bathymetry, vegetation), boundary conditions (e.g., sea level), and projects (e.g., implementation of marsh creation projects). We will detail the accuracy of surrogate models at predicting hydrodynamic outcomes and discuss how these models can enable new planning capabilities for the Master Plan. By enlisting the aid of surrogate models, policymakers and stakeholders can more easily comprehend and implement effective coastal protection strategies. This approach not only enhances predictive capabilities but also fosters a deeper understanding of how nature-based solutions can contribute to coastal resilience.