sessions 61-70
Wednesday, May 21 | 4:00 – 5:30 p.m.
Sessions
• #61 Update on Coastal Resiliency Efforts in Texas Chenier Plain
• #62 The Role of Insurance in Storm Mitigation and Recovery
• #65 Understanding Sediment, Shorelines, and Ecosystem Recovery
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 286
#61 Update on Coastal Resiliency Efforts in Texas Chenier Plain
Since SOC 2023 the Texas Water Development Board (TWDB) adopted the Texas’ inaugural 2024 State Flood Plan on August 15th, 2024, which was delivered to the Legislature on September 1, 2024. Of the roughly 615 flood mitigation projects in the inaugural 2024 Texas State Flood Plan, three (3) Texas coastal flood mitigation projects ranked in the top ten; 1) Coastal Texas Project (CTX) ranked #1, 2) Sabine Pass to Galveston Bay Orange County Project ranked #4 and, 3) Sabine Pass to Galveston Bay Port Arthur Project ranked #9.
The Coastal Texas Giga Project includes 22 separate features/sites that include 8 ecosystem restoration projects along the entire Texas coastline, surge protection gates in the Bolivar Roads inlet to Galveston Bay, structural improvements to the existing Galveston Seawall, a 18-mile ring levee system around the back side of Galveston island, 43 miles of nature-based dunes and beaches on fronts of Galveston Island and Bolivar Peninsula, surge protection gates at both Clear Lake and Dickinson Bayou on the mainland, a beach and dune renourishment measure on South Padre Island, and various non-structural measures where needed to fill in the gaps.
The Sabine Pass to Galveston Bay Orange County includes construction of new infrastructure to reduce the risk of storm surge impacts at Orange County, Texas and the Sabine Pass to Galveston Bay Port Arthur project includes the construction of levees, floodwalls, pump stations and drainage structures.
The total estimated first cost for the three coastal projects in 2022 dollars is approximately $40 Billion.
Moderator: Greg Grandy – Coastal Protection & Restoration Authority
Panelists:
• Ray Newby – TxDOT Maritime Division
• Tressa Olsen – Texas Water Development Board
• Nicole Sunstrum –Capitol Law & Consulting Group
• Tony Williams – Texas General Land Office
Organizer: Augusto Villalon – Freese & Nichols
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 287
#62 The Role of Insurance in Storm Mitigation and Recovery
As coastal communities face mounting risks from natural disasters, skyrocketing insurance premiums, and inequitable recovery outcomes, innovative approaches to insurance and resilience are urgently needed. This session explores the intersection of insurance, disaster recovery, and resilience-building, offering insights into how communities can navigate these pressing challenges. Presentations will address Louisiana’s insurance crisis, emphasizing how homeowners can implement mitigation measures to reduce premiums and enhance property resilience. Research on insurance litigation after Hurricanes Laura and Delta reveals disparities in recovery outcomes, highlighting the systemic barriers many residents face in securing claims. Innovations like parametric insurance models are explored as potential tools for expediting disaster recovery, although findings suggest community engagement is critical before adopting such alternatives. The role of Nature-Based Solutions (NbS) in reducing flood risks and insurance costs will be examined through Florida case studies, illustrating how these strategies, especially when paired with traditional mitigation methods, can create cost-effective pathways to resilience.
Moderator: Charles Sutcliffe – National Wildlife Federation
Presenters:
• Md Adilur Rahim – LSU Agricultural Center
• Abbey Hotard – University of South Alabama
• Jason Bird – Jacobs
Assessing Homeowner Insurance: Mitigation Measures Across Multiple Perils
Md Adilur Rahim – LSU Agricultural Center
Homeowners in Louisiana are facing a significant insurance crisis with skyrocketed premiums, insurer insolvencies, and regulatory challenges. Louisiana now has the highest average homeowner insurance premium in the United States, reaching $2,037 annually. The withdrawal of major insurers has forced many homeowners to rely on state-backed insurers, often at substantially higher premiums. Despite legislative efforts to attract new insurers, such as allocating $45 million to the Insure Louisiana Incentive Program, the state-level interventions have had limited impact. This crisis calls for urgent needs for homeowners to understand and implement mitigation measures to enhance property resilience and reduce insurance premiums. This study assesses homeowner insurance to analyze the effects of various mitigation measures across multiple perils. We conducted exploratory data analysis of rating factors from leading insurance providers to understand how building and policy attributes influence premiums. Our findings show that homeowners can lower insurance premiums and improve community safety by implementing targeted mitigation strategies. Homes constructed with resilient materials, equipped with reinforced roofing, or enhanced with security systems benefited from significant premium reductions. The insights from this study will assist homeowners, builders, and policymakers in understanding how specific mitigation measures influence premiums across various perils. This offers a pathway toward more affordable and sustainable homeownership amidst the ongoing insurance challenges.
Innovating Insurance for Coastal Resilience: Evaluating payment timing & disaster recovery
Abbey Hotard – University of South Alabama
Insurance is a critical tool for mitigating financial losses from natural hazards and enabling recovery. However, rising premiums and long wait times for payments undermine the efficacy of insurance to provide financial resilience to future disasters. Proposed innovations within the insurance market aim to address these challenges by reducing payment delays and easing insurers’ administrative burdens. For example, parametric insurance models typically provide a predetermined payment to policyholders based upon hazard-related metrics (e.g., hurricane wind speed). While largely untested, these policy innovations could significantly improve resilience of coastal communities by enabling more efficient financial recovery. Using original survey data collected in 2024 from homeowners affected by Hurricane Ida in Louisiana (2021) and Hurricane Ian in Florida (2022), this research aims to 1) measure the effect of the insurance payment timing on the pace of disaster recovery and 2) assess desirability of an alternative parametric insurance model. As expected, preliminary survey results suggest that longer wait times for insurance payments are associated with slower disaster recovery. Interestingly, respondents largely preferred traditional insurance over parametric models when presented with a hypothetical scenario. Innovations in the insurance market are essential for accelerating disaster recovery in coastal communities. However, the findings of this research highlight the need for intentional community engagement before piloting similar insurance innovations.
Nature-based Solutions Insurance Impacts
Jason Bird – Jacobs
The many benefits of Nature Based Solutions (NbS) have become clear in recent years, leading to an industry-wide shift to embrace them and identify ways to incorporate them into many of our projects. This awareness has also resulted in many state and federal funding programs requiring the use of NbS, or at least demonstration of a projects benefits to the natural ecology. New state and federal policies are also beginning to drive the application of NbS.
While these new requirements and industry trend are helping to enhance the natural ecosystems that many of us rely upon, there is another benefit of NbS that has been explored in recent years… reductions in flood insurance premiums.
Through a review of Florida case studies, this presentation will discuss how NbS can contribute toward reducing risk within coastal environments, along with the additional benefits provided when NbS are coupled with conventional hazard mitigation strategies as part of a hybrid approach and how these risk reductions can translate to a reduced hazard insurance premium.
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 292
#64 The Bayou Culture Collaborative (BCC) Culture and Planning Working Group: Striving for Community-Centric Adaptation
The Louisiana Folklore Society established the Bayou Culture Collaborative (BCC) to create a communication and support network for individuals concerned about the future of Louisiana’s coast and culture. This group unites practitioners, community members, tradition bearers, and researchers to explore the connection between ecology and culture, as well as the significance of place and community ties to the land—especially in the face of coastal erosion, climate change, and other environmental threats. The BCC investigates community-centered adaptation strategies, including ecological restoration, documentation and preservation of cultural practices, community-based disaster and resilience planning, and trauma prevention.
Panelists will share challenges and lessons learned from their work, engaging the audience in exploring strategies to mitigate the serious social and mental health impacts that coastal and bayou communities face amid disasters and land loss. With input from the audience, the panel will also discuss the collective strengths and cultural assets of these communities and how they can be celebrated and supported
Moderator: Simone Domingue – Tulane University
Panelists:
• Elizabeth English – University of Waterloo
• Cherie Matherne – Pointe-Au-Chien Indian Tribe
• Ivy Mathieu – Bayou Culture Collaborative
• Erin Tooher – University of Louisiana at Lafayette
Organizer: Simone Domingue – Tulane University
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 290
#65 Understanding Sediment, Shorelines, and Ecosystem Recovery
This session explores strategies for identifying and managing sediment resources while assessing the ecological impacts of restoration efforts. Presenters will highlight geologic frameworks that improve sediment sourcing efficiency, ensuring sustainable restoration. Research on post-dredging recovery at Ship Shoal will provide insights into how benthic productivity responds over time, informing best practices for sediment extraction. A quantitative study of oyster reef living shorelines will evaluate wave attenuation and stability, guiding improved coastal protection designs. Finally, an analysis of long-term vegetation trends on restored barrier islands will reveal how plant communities evolve and respond to major storms. Together, these presentations offer a holistic approach to optimizing sediment use and restoration effectiveness.
Moderator: Mark Byrnes – Applied Coastal
Presenters:
• Rob Hollis – The Water Institute
• Stacy Calhoun-Grosch – Louisiana Universities Marine Consortium
• Whitney Thompson – Southern Shores Engineering
• Elizabeth Granier – Nicholls State University
Utilizing geologic frameworks for efficient sediment resource identification
Rob Hollis – The Water Institute
The 2023 Coastal Master Plan identifies a need for 1,046 million yd3 (MCY) of sediment for restoration over a 50-year time horizon (CPRA, 2023). The current inventory of economically-accessible, compatible, sediment is limited compared to the need for future restoration projects. Identifying, and later, developing sediment resources into actionable sediment reserves requires a significant investment of time and funds. Building upon efforts under the Louisiana Sediment Management Plan (LASMP), two case studies efficiently identify sediment resources utilizing source-to-sink geologic frameworks in deltaic and coastal plain settings. Offshore of Barataria Basin, three paleo-delta lobes were mapped containing a first order estimate of 319 MCY of sand and 613 MCY of mixed-sediment. Offshore of the Chenier Plain, several fluvial channel belts were mapped containing a first order estimate of ~900 MCY of restoration compatible sediment. Both these reconnaissance level case studies, expanded the mapping from compatible sediment from previously dredged borrow pits, provided a detailed synthesis of archival data, leveraged focused geophysical and geologic data collection, and suggested areas of refined future investigation. Utilizing source-to-sink concepts, a predictive geologic model was developed to communicate the complex geologic frameworks to a broader audience. These case studies provide a portable strategy to be implemented for similar regions to efficiently create a comprehensive sediment resource inventory for future restoration efforts.
The recovery of benthic production in a sand shoal dredge pit off the coast of Louisiana: How it got here and where is it heading?
Stacy Calhoun-Grosch – Louisiana Universities Marine Consortium
Sand shoals off the coast of Louisiana are relic barrier islands that host highly productive habitats for commercially important fished species. They can also serve as hypoxia refuges for pelagic taxa due to the well mixed water column that is attributed their elevation above the surrounding continental shelf. This raised elevation also promotes high levels of benthic primary production due to increased sunlight reaching the sediments and comprises the base of the food web on these shoals. The sand on these shoals make them prime targets for dredging for coastal restoration projects. Ship Shoal has been the site of two recent dredging projects to restore Caminada headlands (completed in 2017; CAM) and Terrebonne barrier islands (completed in 2022; TER). The timing and depth of the dredging for each of these projects allows us to compare the impacts of dredging over time using a before and after control impact study. This project began sampling prior to dredging in the TER pit and sampling is ongoing to monitor the ecological impacts over time in both TER and CAM pits and un-dredged reference sites (REF). Initially, benthic gross primary production (GPP) and other metrics for the TER pit were most similar to that of REF. One year after dredging, TER was intermediate. We are now examining the trajectory of the impacts to see if TER GPP continues to decrease and become similar to CAM, recover towards rates in REF, or remains intermediate due to shallower dredging depths. Findings from this project can be used to improve future restoration plans and mitigate dredging impacts.
Pearls of Wisdom from the Wave Flume: A Quantitative Study of Oyster Reef Living Shoreline Designs
Whitney Thompson – Southern Shores Engineering
Erosion poses great challenges to coastal management across the U.S. Many stakeholders have deployed living shorelines in an effort to adapt to changing coastal dynamics, in hopes of harnessing ecological benefits. These projects are generally a cost-effective method of reducing shoreline retreat rates while providing benefits such as marine habitat. As such, the deployment of these structures has gained popularity, and many new variations of living shorelines have been developed recently. However, engineering metrics such as wave attenuation, structural stability, and changes to current velocities are rarely validated prior to deployment. A team of consultants, academics, contractors, and NGO’s from Louisiana to North Carolina began efforts in 2024 to quantitatively evaluate the performance of several living shoreline designs so that communities can design systems to meet protection goals with enhanced ecological benefits. A study evaluating field conditions at representative sites was performed to inform critical design forcings for flume study purposes, which was then conducted at the University of South Alabama. Wave attenuation, stability, and current velocities for several different designs were measured during physical modeling. Results from the wave flume study were utilized to calibrate FLOW-3D models. In addition, field monitoring was begun in Bogue Sound, North Carolina and includes evaluating different technologies for wave attenuation capability, shoreline response, and oyster spat recruitment. This presentation will discuss findings from these studies.
Understanding trends in restored Louisiana barrier island vegetation communities through time
Elizabeth Granier – Nicholls State University
TLouisiana’s barrier islands are transient coastal landforms created by the historic deltaic cycle of the Mississippi River. These barrier islands are currently experiencing a high rate of erosion due to a combination of chronic wave energy exposure and acute, high energy storm events. However, because of the important ecosystem services provided by these landforms, including overall storm energy reduction, protection of mainland marshes, and the provision of crucial stopover habitat for migratory birds, Louisiana has invested heavily in the restoration of these ecosystems. Restoration typically involves nourishment of the sand and sediments that comprise these coastal landforms followed by the planting of appropriate vegetation and installation of sand fencing to retain these materials. Although the species selection and plantings protocols for effective, initial barrier island restoration are largely well developed, long term trends in vegetation community succession have not yet been thoroughly evaluated. To address this potential knowledge gap, existing monitoring data from the CPRA BICM program has been subjected to a series of ordination analyses to elucidate successional trajectories and refine knowledge of barrier island vegetation associations. Preliminary analyses of the Timbalier Island Dune and Marsh Restoration project (TE-40) data set using NMDS suggest a shift towards less coverage of planted grasses and natural colonization by vines and asters through time. Further, a clear shift in vegetation communities before and after major hurricanes can be discerned.
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 289
#66 Advancing Sea Level Rise Research to Improve Awareness and Coastal Decision Making in the Gulf
The 2018 NASEM report Understanding the Long-Term Evolution of the Coupled Natural-Human Coastal System: The Future of the U.S. Gulf Coast concluded that sea level rise will significantly affect Gulf coastal ecosystems and communities. The report highlighted one key research gap relating to improving the future of the Gulf Coast: to understand and project the future of coastal landforms and whether they can keep pace with relative sea level rise. Improving projections is a complicated, necessary process that can improve natural resource management, restoration activities, and the resilience of Gulf communities. This proposed session will include presentations from the Gulf Research Program’s Gulf Sea Level Variation and Rise grantees and will focus on their recent findings on non-subsidence and vertical land motion components of Gulf sea level rise, while incorporating these factors into relative sea level rise forecast models and century-scale projections. This session will also highlight effects felt in the Gulf from changes in the volume of the global ocean due to the expansion of warming waters and the melting of glaciers and ice sheets; changes in the earth’s gravitation, rotation, and deformation caused by redistributions of land ice and water; and the dynamics of atmospheric and oceanic processes within the Gulf region (e.g. the Loop Current). Presenters are part of a collaborative research group that aims to produce research with end-use applicability, increase public understanding of the complexity of sea level rise, and meaningfully engage with community partners.
Moderator: Raúl Flamenco – National Academy of Sciences
Presenters:
• Susan Bates – The Nature Conservancy
• Andrew Delman – University of California, Los Angeles
• Matthew Weathers – Carnegie Mellon University
• Ali Relllinger – Mississippi State University and Mississippi-Alabama Sea Grant
Prediction and Projection of GoM Sea-Level Changes Using Eddy-Resolving Earth System Models
Susan Bates – The Nature Conservancy
Current predictions and projections of future sea-level changes are based on CMIP-class climate model simulations. Although this class of models is capable of simulating global sea-level rise and its basic spatial patterns, they are unable to robustly and accurately predict or project future regional and local sea-level changes because of their limitation in representing complex coastline and bathymetry features and regional ocean circulations with their coarse (~100 km) resolutions. More specifically, sea-level changes within the Gulf of Mexico are closely linked to changes in the Loop Current and its eddies, which cannot be resolved by CMIP-class models. In this talk, we will present results of dynamic sea-level changes (DSLC) from an unprecedented set of future climate projection and prediction simulations using a global eddy-resolving (~10 km) version of the Community Earth System Model (CESM-HR). These high-resolution simulations encompass a broad range of climate projections up to the end of this century under different emission scenarios and an ensemble of initialized decadal prediction simulations designed to forecast short term (1-5 years) DSLC. By directly comparing these high-resolution simulations to a similar set of standard CMIP resolution (~100 km) CESM simulations (CESM-LR), we will show that CESM-HR is not only more realistic in simulating observed sea-level variability and changes during the historical period, but more importantly it projects a significantly larger future DSLC within the Gulf compared to CESM-LR. These findings highlight the needs and benefits of using high-resolution climate models to improve projections and predictions of future DSLC.
Gulf Coast Sea Level Prediction and Attribution Using an Ocean State Estimate
Andrew Delman – University of California, Los Angeles
In recent decades, sea level along the U.S. Gulf Coast has risen at a rate exceeding the global mean. Sea level variations on the Gulf Coast are also very coherent from Florida to Texas at seasonal to multi-year timescales, but the causes of both the fast rise and coherent variability are not well understood. This study employs the data-assimilating Estimating the Circulation and Climate of the Ocean (ECCO) state estimate to relate Gulf Coast sea level changes to air-sea fluxes, both locally along the Gulf Coast and remotely in the Atlantic basin. ECCO generates adjoint sensitivities that quantify the impact of fluxes at given locations and lead times on relative sea level variability. Hindcasts that convolve these adjoint sensitivities with fluxes from ECCO and seasonal prediction models have shown encouraging improvements to sea level predictions along the U.S. Gulf coast. ECCO adjoint sensitivities also enable direct attribution of the air-sea fluxes that drive sea level variability, so that the relative contributions of atmospheric forcing in the Gulf, Caribbean, and greater Atlantic basin can be quantified. This adjoint-based attribution framework can be used with existing prediction and climate models to identify why some models are more accurate than others, and assess the prediction skill impact of atmospheric forcing compared to other influences (e.g., mesoscale ocean dynamics unresolved by the ECCO state estimate). An emphasis will be placed on the information that state and local agencies and other end users can incorporate into coastal hazard planning and assessments, such as how large-scale climate variability may impact sea level variability along the Louisiana coastline.
Facilitating dynamic adaptive pathways for GoM decision-makers: land ice and water projections
Matthew Weathers – Carnegie Mellon University
Regional sea-level rise in the Gulf of Mexico is projected to increase flood risks, exacerbate erosion and loss of land, and harm freshwater resources. Dynamic adaptive policy pathways is an approach that enables coastal planners to identify a series of possible adaptation strategies that address short-term needs while maintaining flexibility to address future impacts depending on how future conditions develop. Underlining the dynamic adaptive policy pathways are probabilistic projections for various climate scenarios as well as an observational system that can be used to support the generation of the adaptation strategies and the timing of when decisions need to be made. Our team is seeking to refine projections of global mean sea-level rise based on contributions from glaciers and changes in land water storage and use reverse sea-level fingerprinting to improve probabilistic projections of regional sea-level rise. These projections will be used to develop a tool that supports the use of dynamic adaptive policy pathways. Here we provide an update of the latest scientific findings and an overview of the path forward.
Improving translation and application of sea level rise science in the Gulf
Ali Relllinger – Mississippi State University and Mississippi-Alabama Sea Grant
Sea-level rise presents a wide array of environmental and community challenges across the Gulf region. As a result, climate resilience practitioners need to translate the best available, locally relevant science to decision makers, educators and the community. This presentation will provide an overview of some of the existing tools used to communicate sea-level rise science in the Gulf as well as highlight two ongoing efforts to improve the translation and application of new science. The first is through stakeholder informed development of an adaptation pathways planning tool. We will present results from focus groups conducted across the region to share current needs identified by a variety of stakeholders such as municipal planning staff and natural resource managers. The second is through the development of a Gulf sea-level rise storymap designed to communicate the goals and objectives (and ultimately the results) of three ongoing research studies funded through the Gulf Research Program’s Gulf Sea Level Variation grants. This effort includes collaboration with each research team to develop plain language information about each project which is accessible to a variety of semi-technical end-users but maintains fidelity to the research objectives and findings. This includes highlighting some of the challenges and solutions to developing this type of communication. Overall, the audience will gain an understanding of a variety of needs on the pathway from science to decision making to successfully apply sea level rise science to problems facing Gulf communities.
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 288
#67 Developing Integrated Engineering and Design Solutions (DEEDS): Foundations and Partnerships
Ecosystem restoration is defined as “the action of repairing sites in nature to their former function or condition.” Climate impacts negatively impact coastal ecosystem functionality, communities and infrastructures. Consequently, restoration efforts are proposed that harness natural and nature-based features (NNBF) to build land and protect assets. However, restored landscapes scarcely resemble what previously existed. Approaches proposed within restoration frameworks are design-oriented processes, though landscape designers are rarely involved in their development and implementation. The LSU Coastal Ecosystem Design Studio, with support of the USACE Engineer Research and Development Center through the Developing Integrated Engineering and Design Solutions (DEEDS) project, has developed a Collaborative Ecosystem Design (CED) approach to the development of coastal NNBF. The CED framework focuses on environmental co-benefits associated with NNBF in the Gulf of Mexico and strives to develop ‘design-criteria’ that quantifies the relationships among ecosystem structure and processes with ecosystem service valuations to reduce uncertainty in evaluating social benefits. This presentation will highlight work within DEEDS that engages university students from across the world, and across disciplines, to improve NNBF and support community partners along the Gulf Coast.
Moderator: Fabiana Trinidade da Silva – Louisiana State University
Panelists:
• Dov Block – St. John the Baptist Parish
• Joseph Brooks – Louisiana State University
• Casey Jones – University of California Berkeley
• Jacob Midkiff – Louisiana State University
• Yao Wang – Louisiana State University
Organizer: Traci Birch – Louisiana State University
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 285
#68 Predicting, Monitoring, and Managing Crevasses in The Lower Mississippi River
The Mississippi River Delta a century from now will be smaller than the Mississippi River Delta of today – there is not sufficient sediment in the river’s transport system to maintain the delta’s land area in its current form. But the river’s own transport system provides an efficient delivery mechanism for sediment to be used in the task of maintaining valuable habitat and land area in the delta, giving coastal managers in Southeast Louisiana a unique tool to mitigate land loss and prioritize sediment delivery and retention for land building in target areas. The use of carefully managed diversions with control structures has been explored extensively from the perspective of mitigating the risk to navigation while maintaining delta land area, but the recent history of unexpected crevasse expansion in the lower river points to a need to more deeply understand how to predict, monitor, and manage free flowing crevasses that lack a control structure. In this effort there is a wealth of knowledge, data, and experience gained from working in free flowing crevasses as varied as West Bay, Neptune Pass, and the network of intentional crevasse cuts in the Lower Birdsfoot. This session invites presentations of observational or theoretical results that can be applied to improve the understanding of how crevasses occur, how they can be controlled without hard engineered control structures, and how they can be manipulated at the inlet or from the basin side to improve management outcomes.
Moderator: Christopher Esposito – The Water Institute
Lightning Presenters:
• Christopher Esposito – The Water Institute
• Matthew Czapiga – Tulane University
• Madeline Foster-Martinez – University of New Orleans
• Katelyn Keller – Army Corps
• Cassidy Lejeune – Ducks Unlimited
• Ioannis Georgiou – The Water Institute
• John Nyman – Louisiana State University
• Todd Baker – CPRA
• Gary L. Brown – USACE
• Brendan Yuill – USACE
Organizer: Christopher Esposito – The Water Institute
Mapping and Classification of Crevasses in the Mississippi River Delta
Christopher Esposito – The Water Institute
Managing the Lowermost Mississippi River as a navigation conduit, potential flood hazard, and environmental resource is a complex task requiring coordinated decision-making among multiple entities with varying, sometimes conflicting, interests. This challenge will grow in the coming decades as strategic decisions (e.g., managing the deteriorating east bank) intersect with accelerated changes in sea level and precipitation patterns that shape the system’s boundaries. To address this, the Coastal Protection and Restoration Authority of Louisiana (CPRA) seeks strategies that align with its interests and encourage cooperation with other stakeholders. The Water Institute has developed a tool to automate the execution of a HEC-RAS model that simulates water and sediment flow throughout the Lowermost Mississippi River and its distributaries and outlets. This tool enables thousands of HEC-RAS model runs, allowing researchers to evaluate proposed strategies for vulnerabilities within a formal Robust Decision Making (RDM) framework across a range of environmental forces and decisions, and improve them iteratively. Additionally, the tool reveals trade-offs between management strategies for different objectives and how they may shift under future scenarios. The RDM framework was applied to three strategies: Business as Usual, where decision-making continues as it does today; an Alternate Navigation Channel strategy, where the main river channel is abandoned for deep draft navigation south of Empire in favor of a new channel; and an Adjusted Flow Split strategy, which changes the 70/30 flow division between the Mississippi and Atchafalaya Rivers.
Basin Controls on the Channel Morphodynamics of Juvenile Deltas
Matthew Czapiga – Tulane University
The earliest delta formation is largely controlled by fluvial processes due to their small size, rather than tidal or wave effects at the delta shoreline. The evolution of these growing deltas depends on the channel formation process, which controls how water and sediment are conveyed down delta. Here we discuss application of a reduced complexity morphodynamic delta model with self-formed channels that was built to understand the concurrent evolution of delta advancement and channel evolution. Delta advancement rate has been long defined to scale with the ratio of sediment load and basin accommodation space, i.e. the volume to be filled. Our numerical tests show that basin accommodation is necessary, but insufficient to explain how channels form on the delta top. As accommodation is reduced, the delta continually creates new channels at the rapidly advancing shoreline. Deltas advancing into larger basins grow slower but develop more mature channels and proportionally more of the delta is visible (subaerial). How basin volume is oriented affects channel geometry on the delta top. We find self-similar channel geometries when basin volume is increased vertically (via basin slope or depth), but it breaks down when accommodation is increased laterally via the confining basin width. This occurs because widening the delta plain increases inter-channel areas and reduces both flow confinement and transport capacity in the main channels. This study has implications for land building in the Mississippi Delta at controlled or uncontrolled diversions, such as Neptune Pass
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.
Analysis of the Use of Scour-Resistant SREDS to Control Discharge and Induce Land-Building at Neptune Pass: a Numerical Model Investigation of Hydrodynamics and Morphologic Change
Katelyn Keller – Army Corps
Neptune Pass is a crevasse through the East Bank of the Lowermost Mississippi River (LMR), across the River from Buras, Louisiana. Following the exceptionally high 2019 spring flood event, Neptune Pass rapidly expanded from an historically small channel to a significant LMR distributary. Currently, the crevasse measures an average of 800 ft in width and diverts 14.5% – 20% of the LMR flow at that location. This increased discharge has resulted in several negative impacts on stability of the LMR navigation channel. These include impacts to navigation safety associated with currents through the Pass, as well as significant induced shoaling in the navigation channel just downstream of the Pass. In addition, river discharge lost through the Pass at low water is associated with increased salinity intrusion in the LMR. Conversely, there are indications that the expansion of Neptune Pass is promoting positive impacts on environmental quality. Recent aerial imagery and observations show that sediment conveyance through Neptune Pass is aiding land building in Quarantine Bay and Bay Denesse, the receiving waters for Neptune Pass. To address these issues, a solution was proposed whereby the discharge through Neptune Pass is controlled with a rock sill at the upstream end of the Pass, and a series of shear-resistant Sediment Retention Enhancement Devices (SREDs) at the downstream end of the Pass. The solution is designed to mitigate navigation concerns while minimizing impacts on flow and sediment diversion at the Pass. The shear -resistant SREDS are also designed to induce deposition of sediments, thereby accelerating land-building processes.
An Overview Ducks Unlimited’s Delivery of Crevasse Projects in the Lower Mississippi River Delta – How, Where, and Why
Cassidy Lejeune – Ducks Unlimited
For 87 years, Ducks Unlimited has protected, restored, and enhanced wetlands across North America to provide habitat for waterfowl, other wildlife, and people. A top level priority area for Ducks Unlimited is the Gulf Coast because of its importance to wintering waterfowl. Ducks Unlimited has delivered conservation projects in south Louisiana since the mid-1980s and the magnitude of delivery is currently greater than ever. The use of “crevasses” or mini freshwater/sediment diversions are one of many techniques used by Ducks Unlimited to restore and enhance coastal marshes. Through partnerships at the state and federal levels, Ducks Unlimited has delivered several crevasse projects on public lands in the lower Mississippi River Delta over the past few decades. This presentation will share Ducks Unlimited’s means and methods to deliver crevasse work and provide an brief overview of past accomplishments. It will highlight how crevasse projects are developed, where the are constructed, and why Ducks Unlimited feels they are a useful tool for building wetlands.
Growth laws for Sub-Delta Crevasses in the modern Mississippi River Delta
Ioannis Georgiou – The Water Institute
Understanding delta morphology is essential for predicting land formation and managing delta systems, but field observations are often sparse. Here, we investigate the growth patterns for anthropogenic sub-delta crevasses (SDCs) in the Mississippi River Delta (MRD) to determine whether their features follow established scaling laws observed in natural deltas and laboratory delta analogs. SDCs provide a unique opportunity to bridge the gap between laboratory deltas and larger natural deltas, enabling rapid observations and insights into their geomorphic evolution without the scaling limitations of laboratory deltas or the slow development timescales of natural deltas. Our results indicate that, with some exceptions, SDCs generally conform to growth laws similar to those of river-dominated deltas but exhibit deviations in channel bifurcation length and wetted area metrics due to frequent channel splitting and varying development rates, suggesting that downstream or basin-specific controls may play a significant role. These findings underscore the importance of SDCs as a model for understanding deltaic processes, enhancing our understanding of crevasses evolution, and refining restoration strategies for the MRD.
When Should We Abandon Wetlands in the Bird Foot Delta?
John Nyman – Louisiana State University
The primary function of the Mississippi River’s Bird Foot Delta depends on channelized flow in the navigation channel to export crops and fossil fuels. Optimized for navigation, the Bird Foot would have one outlet. The 2nd most important function depends on the transition from channelized to unchannelized flow to sustain wetland-dependent fish and wildlife. Optimized for fish and wildlife, secondary outlets would be numerous, long and bifurcating. Some people have argued that the Bird Foot wetlands should be abandoned now because (i) Bird Foot wetlands were created by abnormal sedimentation from 1850 to 1950 associated with converting the Midwest from prairie to agriculture, (ii) the Bird Foot receives less sediment and freshwater than it did before upstream dams, channel armoring, and faster sea level rise, and (iii) recent wetland loss proves that subsidence and sea-level rise are too rapid to sustain Bird Foot wetlands. This talk will challenge those ideas with (i) geologic data showing two cycles of subdelta creation and subsidence under the subdelta created by the crevasse of 1838, (ii) the idea that the Bird Foot may now receive more water and sediment than it did before 1900 when the spring flood was spread over the inactive deltas as well as the Bird Foot and (iii) wetland loss data showing that the Bird Foot has sustained ~78,000 wetland acres from the 1970s through 2016.
History of crevasses and their importance to wildlife and fisheries
Todd Baker – CPRA
Crevassing has been strategy to manipulate riverine waters of the lowermost Mississippi River since 1830. Early crevasses were built primarily for navigation and accessibility purposes, but have recently evolved to the most cost efficient tool to build wetlands in coastal Louisiana. Over the last 195 years crevassing has built more than 100,000 acres of delta splay marshes south of Venice. These crevasses build a wide variety of ecosystems from submerged aquatic grass beds, to tidally influenced mudflats and marshes, to coastal forested ridges. These habitats combined with their unique position between the Mississippi River and the Gulf of Mexico host some of the most abundant and diverse assemblages of wildlife and fisheries in North America.
Mitigating Uncontrolled Crevasse Formation by Building Land: A Strategy for the East Bank of the Lowermost Mississippi River
Gary Brown – USACE
Brendan Yuill – USACE
Downstream of Point a la Hache, Louisiana, the East Bank of the Lowermost Mississippi River (LMR) is not protected with a Federal Levee. During high flows on the LMR, uncontrolled crevasses through the East Bank can form and grow rapidly. Between Point a la Hache and Boothville, the extant uncontrolled crevasses along the East Bank divert ~30% of the LMR discharge. This flow diversion can have significant effects on navigation, both with respect to navigation safety and dredging, and can also impact the likelihood and extent of salinity intrusion in the LMR during low flows. Traditional solutions to crevassing often involve closure of the crevasse with a rock structure. These structures are subject to flanking, and the consequent increased water surface elevation in the river can increase the discharge in nearby uncontrolled diversions. To address these deficiencies, an alternative system-wide solution has been proposed. This solution induces the acceleration of wetland growth in the receiving waters, thereby reducing the probability of crevassing by increasing the frictional resistance between the river and the receiving waters. This acceleration of wetland formation is accomplished by modifying traditional Sediment Retention Enhancement Devices (SREDS) to be robust, scour resistant structures that can be placed at the outlets of existing crevasses. These scour-resistant SREDS serve both to restrict discharge through the crevasses, and to induce eddy formation and deposition in the lee of the SREDS. The results of a numerical hydrodynamic and morphological investigation of a system of scour-resistant SREDS are summarized in this talk.
Wednesday, May 21 | 4:00 – 5:30 p.m. | Room 284
#69 Morganza to the Gulf Hurricane Risk Reduction System: Protecting the Community and Restoring the Environment
The Morganza to the Gulf Risk Reduction System (MTG) is a hurricane and storm damage risk reduction project that is part of the Mississippi River and Tributaries (MR&T). The project will reduce the risk of flooding due to storm surge to more than 52,000 structures and over 200,000 people in an area of intense concentration of energy infrastructure near the confluence of two nationally significant navigation corridors in the Mississippi River and the Gulf Intercostal Water Way (GIWW). The project is 98 miles in length and consists of earthen levees, floodgates, environmental water control structures, road/railroad gates and fronting protection for existing pump stations. Major project features are two floodgates in the Gulf Intracoastal Waterway (GIWW) and a lock complex on the Houma Navigation Canal (HNC). Prior to the recent federal new start construction funding, CPRA and the local levee districts have invested over $1.1B of in construction on the alignment including the HNC Lock Complex and have seen significant reduction in flood events since the 2008 hurricane season. The Federal new star construction funds are leveraging this work to ensure a completed system is in place before 2030 and to its authorized height by 2035. The MTG project is unique in that the system will be operated to reduce the effects of saltwater intrusion and its effects on interior marshes, specifically the HNC Lock Complex. The project alignment has minimized impacts by constructing along existing hydrologic barriers and addresses connectivity issues by installing water control structures.
Moderator: James McMenis – CPRA
Presenters:
• Dwayne Bourgeois – North Lafourche Conservation, Levee and Drainage District
• Mitch Marmande – Delta Coast Consultants, LLC
• Nicole Buranzon – APTIM
• Lacy Shaw – Army Corps of Engineers
The Importance and Benefits of Managing an Open System
Dwayne Bourgeois – North Lafourche Conservation, Levee and Drainage District
Louisiana understands that we must protect communities from disaster while restoring the environment at the same time. South Louisiana is a foretell for the nation of the challenges to come from, subsidence, rising seas and stronger, more frequent storms. The Morganza-to-the-Gulf Hurricane Protection System (MtoG) exemplifies a unique approach to addressing these issues.
MtoG is a levee, lock, and floodgate system designed to provide 100-year, Category 3 storm surge protection to more than 200,000 citizens living in coastal Terrebonne and Lafourche Parishes, as well as over 1,700 square miles of fresh to saltwater marsh. The project consists of 98 miles of earthen levees, 22 floodgates on navigable waters, 23 environmental water control structures, and the Houma Navigational Canal lock complex.
MtoG has been designed in a way that meets goals of environmental sustainability, climate adaptation, protection of vulnerable communities, and resiliency of critical infrastructure. As an open levee system, MtoG is only closed in the face of storms, allowing hundreds of square miles of marsh to be sustained by the ebb and flow of the tides at other times. While not yet complete, the system is already beginning to show improvements to the wetland areas inside the system. The system protects tens of thousands of residents located in disadvantaged areas per screening tools from the White House Council on Environmental Quality. It also protects an energy hub essential to the current needs of the country and our nation’s energy transition to renewable sources. Essentially, completing and actively managing the MtoG system would provide resilience for communities and restoration of a currently degraded ecosystems on the front lines of climate stress.
Performance of the MTG System Hurricane Francine, Path Forward
Mitch Marmande – Delta Coast Consultants, LLC
Hurricane Francine produced the largest recorded storm surge in Terrebonne Parish exceeding the water elevations of Hurricanes Rita, Ike and Barry. Since 2008, CPRA and TLCD have been aggressively constructing the initial lifts of Morganza to the Gulf (MTG) as work in kind credit to the federal MTG efforts which have just recently begun. This work has yielded a 12-foot level of protection throughout the southern reaches of MTG and nearly 80 miles of first- lift levees with 14 floodgates. These local and state efforts proved their merit during Francine and yielded zero homes flooded with an 11.5-foot storm surge. While these efforts are not currently certified by FEMA there is no doubt that hundreds of millions of FEMA expenditures have been prevented by this initial lift. This hurricane also serves as evidence that our work is incomplete. TLCD and CPRA recognize the need to improve our system and along with USACE have begun efforts to lift the system to 15 feet for the southern and eastern facing reaches and lift Lockport to Larose to an initial elevation of 10. TLCD and CPRA continue to use our experience and successes to prioritize our efforts to efficiently deliver these projects. In concert with the completion of the HNC Lock and the GIWW flood gates we feel positioned to improve flood protection, navigation and the environment throughout Terrebonne and Lafourche parishes.
HOUMA NAVIGATION CANAL (HNC) LOCK COMPLEX (TE-113)
Nicole Buranzon – APTIM
Wetland loss in the Terrebonne Basin can be attributed to a combination of several factors. One primary contributor is the intrusion of saltwater from the Gulf of Mexico into wetland areas initially formed and fed by the freshwater resources of the Mississippi River. Today saltwater infiltrates into fresh wetland areas and the fresh vegetative populations inhabiting these areas are quickly destroyed by the higher salinity levels. The root systems that had previously aided in holding the nutrient-rich but fragile wetland soils together no longer perform that function, causing shoreline erosion rates to increase substantially. The expansion of open water areas leads to more violent tidal action, affecting all aspects of estuarine life for wildlife, fisheries, and the human population. To combat these current currents threats to the Terrebonne Basin, the Terrebonne Levee and Conservation District (TLCD) has partnered with CPRA to construct the HNC Lock Complex. Once complete, this project will provide primary benefits consisting of reduced salinity intrusion, distribution of freshwater in Terrebonne Parish, increase storm surge protection, and increase commerce and navigation capabilities. The HNC Lock Complex Project consists of a 110-ft x 800-ft lock, a 250-ft floodgate, adjacent floodwalls, and other project features that will be constructed to a 100-year annual exceedance probability elevation and with a 100-year design life. Phase I (Dredging and Civil Site work) is complete, Phase II (Lock Complex) is currently under construction. Phase 3 (Bubba Dove Floodgate Retrofit and Floodwalls) is scheduled go to bid in 2026.
Morganza to the Gulf – Federal Participation
Lacy Shaw – Army Corps of Engineers
MTG was authorized for construction in WRDA 2007 based on the 2002 and 2003 Chief of Engineers reports, which were written prior to development and implementation of post-Katrina design criteria. Incorporating post-Katrina design criteria drove the costs more than 20% higher than the cost authorized in WRDA 2007, thereby exceeding the Section 902 Limit triggering the need for reauthorization. As a result, a PAC Report was completed, and a Chief of Engineers’ Report was signed on 8 July 2013 to seek re-authorization of the project. The project was reauthorized in Water Resources Reform and Development Act (WRRDA) 2014 to provide a 100-year level of risk reduction. Since re-authorization, the project team has applied adaptive criteria design and incorporated the work that has been completed on the alignment that updated the cost to $6.5B ($10.2B fully funded through the life of the project) as documented in the EDR approved on 15 December 2021. A Project Partnership Agreement (PPA) was signed on 28 December 2021 utilizing innovative cost sharing and project delivery limiting the federal cost to $2.5B ($4.9B fully funded). The project received $12M in Fiscal Year (FY) 2021 New Start Construction funds for the Humble Canal Floodgate Preload Contract that was awarded September 2022 and completed September 2023. The project also received $378M under the Bipartisan Infrastructure Law along with $19M in FY 22 Community Funds, $31M in FY 23 Community Funds, and $28M in FY 24 Congressional Directed Fund.