As residents of Louisiana prepare for possible disruptions in their drinking water caused by saltwater intrusion, researchers from the U.S. Army Engineer Research and Development Center (ERDC) are assisting the U.S. Army Corps of Engineers (USACE) New Orleans District with assessment and mitigation efforts.
With much of the lower Mississippi River Valley experiencing extreme drought conditions, the lack of rainfall has led to lower levels of fresh water in the Mississippi River, allowing for a denser layer of salt water from the Gulf of Mexico to make its way upstream, threatening the drinking water supplies in several Louisiana communities, including the city of New Orleans.
River conditions are low and have been for some time. The bed of the Mississippi River is much lower than the sea level in the Gulf of Mexico, and if there's not enough fresh water to apply pressure to keep the salt water in the Gulf of Mexico, then it slowly migrates upstream in the shape of a wedge.
“When fluids of different densities encounter each other — which in this case, salt water is denser than fresh water — they tend to stratify,” said Gary Brown, a research hydraulic engineer with the ERDC’s Coastal and Hydraulics Laboratory. “So, the fresh water flows over the salt water, and the salt water flows under the fresh water.”
Salt water has been steadily migrating upstream against the current, and as long as those low river conditions persist, without intervention, that upstream migration will persist.
“Salt is not something that you can conventionally deal with in drinking water filtration,” said Brown. “You can't filter it out of the water, and it corrodes the pipes. It's a significant issue, not only for drinking, but also for agriculture and livestock.”
Though it’s a relatively new term to many, experts at ERDC have been studying these saltwater wedges and intrusion for decades.
“We owe a lot of our knowledge of the salt wedge and salt dynamics to the work that has been done here at ERDC over the years by many different people,” said Brown. “We have much understanding of the basic physics of saltwater wedges, and a lot of that pioneering research was done right here. There was a lot of the early physical and numerical modeling of salt wedges that was developed here, as well.”
To help assess the current conditions, the team is using a basic model they developed with a freshwater layer on a saltwater layer that interact.
“We have a fairly simplified model of the Mississippi River, but it's pretty effective,” said Brown. “It's been successful at predicting where the salt's going to be, and it runs quickly allowing for a lot of ‘what if’ analysis.”
“This is an emergency operation, and we need really quick turnaround of our assessments,” he continued. “We want to be able to do a lot of assessments, not only of what may happen in the future, but also what effects some of our interventions may have. With this tool, we can run very rapid, quick assessments.”
Though ERDC is known for its expertise in research and development, the organization often assists in actionable, emergency operations support — events that are happening right away and impacting a lot of people’s lives immediately.
“Gary and his team have been unwavering in their support to the New Orleans District’s Lower Mississippi River Engineering Branch during this event,” said David Ramirez, chief of the Lower Mississippi River and Tributaries Branch at the New Orleans District. “Their technical assistance by refining an existing hydrodynamic model of the Lower Mississippi River enabled us to respond quickly to this crisis and provide technical information — such as salinity intrusion progress and influence of the natural crevasses along the east bank of the Lower Mississippi River — to USACE leadership and the local governments.”
“The role we play is to try to provide the best information in real-time to support the decision makers,” said Brown. “It's our job to provide the best objective analysis we can — even if that objective analysis is bad news — so that the decision makers can have the opportunity to make the most informed, rational decisions.”
That work is still being used to provide critical data to the Water Management Section and the District Commander, who make real-time operational decisions.
“One of the main products from ERDC is the forecasted salinity locations,” said Ramirez. “The official timeline of when municipal freshwater intakes may be impacted is developed directly from these results. The data is also being used by many local and state government leaders to plan and design saltwater intrusion mitigation strategies.”
“We are working very hard with the district to try to mitigate this issue as much as possible,” said Brown. “We recognize that this is a serious situation for a lot of people in the New Orleans area and the downstream communities. It's a privilege to be able to do something like this and possibly impact people's lives.”
“Gary and his team continue to offer transformative novel, but technically sound, applied solutions to the district at the operational timescale immediately useable for decision making,” said Ramirez. “Cutting-edge technology for decision making today is a rare commodity at the best research intuitions, and we had that luxury through the current emergency saltwater intrusion operations thanks to Gary and the team at ERDC.”
Sliding on ice at speeds exceeding 90 mph is terrifying for most people, but the USA Luge team is seeking assistance from the U.S. Army Engineer Research and Development Center (ERDC) along with academic and industry leaders to go even faster.
In the sport’s rule book, luge is afforded a great deal of engineering leeway to customize their sleds and runners. They have their own team of technicians to manufacture the sleds, and athletes routinely engage in the design/build process making luge not only a competition of technique but also one of technology.
It’s all about moving fast on ice, and as such, the team reached out to Dr. Emily Asenath-Smith, lead of the Ice Adhesion Facility at ERDC’s Cold Regions Research and Engineering Laboratory (CRREL).
“We first started discussions about high-speed ice friction research about six years ago,” said Asenath-Smith. “Ice adhesion and ice friction are both interface phenomena. They are essentially ice interacting with materials, and they are very related research areas.”
“CRREL has worked in this space for a number of years,” she added. “The Army cares a lot about ice friction — whether they are pulling sleds in cold regions or driving vehicles across frozen ground.”
Unfortunately, when USA Luge first contacted Asenath-Smith there wasn’t enough time to develop a productive collaboration.
“They were getting ready for the 2018 Winter Olympics, but because of timelines to make modifications, there just wasn’t adequate time to do the number of studies that we needed to do,” she said.
However, this time when the team reached out in fall 2022, the timelines finally lined up.
“They got back in touch with me, and said, ‘hey we’re ready and pulling together a research team — we have time,’ so we started talking about what our involvement in the luge research team might look like,” said Asenath-Smith. “What research studies could we do at CRREL? How could we support them?”
To explore and ultimately define the partnership, Asenath-Smith and Dr. Austin Lines, a mechanical research engineer and ice friction researcher at CRREL, accepted the invitation to a workshop held in Park City, Utah, in March 2023. This effort solidified the interdisciplinary research and development (R&D) team and established a roadmap to develop approaches that decrease ice friction and increase speed for the luge team.
“USA Luge took a very organized approach to building out an R&D team for their sport,” said Asenath-Smith. “They had some of their industry research experts, me and Austin — we all went to Park City and engaged in extensive discussions, tours and learning for two days. We met athletes, toured the facilities and engaged in deep cross-disciplinary discussions about all the aspects that affect friction and the interaction of ice with materials.”
Consequently, the luge R&D team is now working on an extensive test plan that integrates technologies that are being developed in other CRREL programs, mainly those in the Materials and Manufacturing Program.
“Essentially this effort fits under a portfolio in advanced materials that we have going with the South Dakota Mines,” said Asenath-Smith. “We were able to connect the luge team with them to help engineer new alloys for their runners. Since we already have a relationship with the university, it’s beneficial to us all. We will get to test some of the materials the luge team may be interested in — albeit indirectly.”
Understanding high and variable speed ice friction is of strategic importance not only to the USA Luge team but to U.S. Army operations in the Arctic. While most mobility and traction applications require good adhesion between ice and tire materials, skis and sleds are an important mobilization method where decreased friction can reduce soldier fatigue and reduce fuel consumption. The collaborative efforts between USA Luge and the U.S. Army Corps of Engineers can have a profound effect in the future.
“They have so much liberty to engineer and innovate with their sleds that they are the perfect team to undertake an R&D venture,” said Asenath-Smith. “Ultimately, our success will be determined by the luge team’s success at future Olympic games. There just might be a gold medal on the horizon.”
Natural and nature-based features (NNBFs) are becoming more prevalent in coastal resiliency and protection design as climate change threatens social, economic and environmental systems along the U.S. coast. However, planners need enhanced processes to predict and quantify their benefits prior to implementation.
To better incorporate these designs into numerical models, the U.S. Army Corps of Engineers (USACE) has developed an Engineering With Nature® toolkit for the Coastal Storm (CSTORM) Modeling System, enabling planners to test the hydrodynamic, ecologic and adaptive effects of NNBFs on coastal or estuarine environments.
“The EWN toolkit for CSTORM modeling is a graphic user interface, or GUI, that allows a numerical modeler to represent NNBFs digitally in existing numerical models and standardizes and streamlines the augmentation of those features into the modeling framework,” said Dr. Amanda Tritinger, a research hydraulics engineer with the U.S. Army Engineer Research and Development Center and assistant program manager for the USACE EWN initiative.
The initiative uses the intentional alignment of natural and engineering processes to efficiently and sustainably deliver economic, environmental and social benefits through collaboration. As projects are planned, USACE districts require a method for predicting the impact that EWN features — such as NNBFs — may have on the coastal resiliency of communities, quantifying changes to predicted values of storm surge, inundation and wave attenuation for various storm events if these features were implemented.
Traditionally, the process for bringing these features into numerical models has been cumbersome and expensive. The modeling requires manual integration into the bathymetry/mesh, entailing a high level of skill and a significant time commitment. Each time the feature is altered, the mesh must be rebuilt, causing significant time delays.
“This new tool lets you get a preview of what your meshed-in feature will look like,” said Tritinger. “It also lets you drag and drop multiple designs in one at a time and choose alternative ideas to see what could work and what doesn’t. I think it gives engineers the thumbs up to try something different. It’s more than just a tool -- it’s the chance to push the line of innovation on engineering design.”
The tool doesn’t only open the door to innovation, but also to efficiency.
Standardization is an important key to the framework’s success. The CSTORM design team put a lot of effort into the literature review, working to consistently set the parameters of the numerical model.
“Before, you had to do this extensive literature review to figure out how to represent your features and the parameterization settings of your numerical modeling,” said Tritinger. “We’ve brought all the literature together and put it in one place in this GUI. It allows the user to see the metadata, where the numbers come from, and use their own expertise to adjust as needed.”
Interested districts can download the GUI by visiting the Aquaveo website or learn more information about the toolkit at the EWN website.
“There is also material on the EWN website supporting the toolkit,” Tritinger said. “I think that’s really important for actual application. It’s one thing to have the tool, it’s another to know how to use it. Hopefully this tool, and the documentation behind it, can empower the districts to quantify and understand effects of more resilient designs.”
As part of the EWN initiative, researchers hope to see more widespread usage of the EWN toolkit across the enterprise as the tool can be used to streamline mesh development in general for numerical modeling.
“I would highly recommend – even if you don’t have interest in NNBFs – to take a look, download it, and apply it to mesh development even outside the Advanced Circulation Model,” said Tritinger. “Because of the new workflow, you can develop a mesh and apply it to your own models. It does more than augment an NNBF into a numerical modeling framework. It can expand innovation on every project.”
The U.S. Army Engineer Research and Development Center (ERDC) is collaborating with the Navy to reinforce quay walls, which are areas around a wharf or pier that hold back dirt.
ERDC’s Coastal and Hydraulics Laboratory (CHL) recently hosted a materials workshop for the Seabees of Naval Mobile Construction Battalion (NMCB) 11, assigned to Naval Construction Group TWO and stationed in Gulfport, Mississippi.
An offshoot of the laboratory’s quay wall improvement project, the group explored the method of using fiber-reinforced polymer (FRP) material to build sheet pile walls.
A quay wall extension usually has a deck on top that can be used for loading or unloading a boat. Sheet piles are sections of sheet materials with interlocking edges that are driven into the ground to form the wall. Traditional sheet piles are made of steel; however, FRP is a composite material made of a polymer matrix reinforced with fibers.
“It’s an improvement over steel, because it’s a lot lighter,” said Capt. Patrick Border, a research engineer with ERDC-CHL. “It’s a lot cheaper and reduces the amount of equipment needed to handle it, which makes it attractive for uses in remote locations. It’s also resistant to environmental factors like sea water and ultraviolet.”
“You can cut it into a variety of lengths either ahead of time or on site,” he said. “The material can be shipped inside CONEX boxes and can even be picked up by hand with just a couple of people. It’s very easy to work with, and it’s quick to construct.”
The Navy became interested in the material after completing a quay wall restoration project with ERDC-CHL earlier this year.
“We collaborated on a project in Gulfport where we built a small extension of a pier out of the quay wall material,” said Border. “It worked out pretty well, so they wanted to send some of their builders up here to train on the material.”
With the success of the workshop, the laboratory has hopes of expanding into a broader program.
“Hopefully, this year or next year we’ll have another group coming through,” said Border. “We currently don’t have a formalized class, but we are trying to move in that direction.”
In the meantime, CHL has a few more renovation projects coming up that will benefit from the use of the FRP sheet piles.
“We have projects at Camp Shelby and the Port of Gulfport,” said Border. “There’s two on islands — one in the Atlantic and one in the Pacific — that have been identified for quay wall restoration with this material.”
“From the Army’s point of view, we used to have a lot of capability to repair ports, but that’s weathered away over the past couple of decades,” he added. “We are trying to get back into that, and this new material will make it much easier to do larger construction missions.”