More than 70 years after the end of World War II, there are still thousands of tons of unexploded bombs across Europe. Some are underwater, like the one that detonated earlier this fall, in a channel near the Baltic Sea, during an attempt to defuse it. While no one was hurt in that incident, an impressive plume of water exploded high into the air, displaying the incredible power that still lurks beneath.

Discovery and recovery of unexploded munitions — left over from military activity — continues. Jack Puleo, Chair of the University of Delaware’s Department of Civil and Environmental Engineering, is on a mission to help find them, or, at least conduct research and create the technology that will make the process easier.

“In a perfect world, the munitions would be collected and disposed of safely,” Puleo said. “But when metal is left out in nature it can expand and corrode, changing in volume, density and weight. That will change how the object behaves daily or in an extreme event, and whether it will sink or move on.”

One aspect of the problem is understanding how the munitions migrate or bury in the natural environment. Another aspect of the problem is understanding the natural environment itself, particularly sediment transport and sand elevation changes that may entomb a munition or cause it to become exposed to waves and currents. The sea bed evolves on a wave by wave basis as sand is mobilized from one location and deposited in another location.  However, no commercially available instrument exists for measuring or estimating these sediment transport processes occurring near the sea bed. It is important to find the historic munitions because of the safety risk they pose as active munitions, as well as the potential environmental impact. Beyond identifying the process of munitions burial and migration, studying and understanding sediment transport is important for coastal communities impacted by storm surge and flooding, which can be leading causes of loss of life and property in those localities.

More accurate models — built through better data and measurement collection — will enhance predictive flood mapping, better inform evacuation orders, and aid in the development of resilient coastal communities. To get there, scientists need improved sensing methodologies that will help them understand these processes.

Thanks to Puleo, a better option will soon be available. Over the summer, Puleo received two new grants to bolster his work in coastal engineering innovation, and specifically his research into a sensor that will help researchers understand how such materials may move underwater. The investments, from the Strategic Environmental Research and Development Program and the National Science Foundation, speak to the unique strengths Puleo and his fellow researchers are honing around coastal engineering and this specific challenge.

The awards are also a point of pride for Puleo as a mentor — his former student Ryan Mieras took the lead to submit the National Science Foundation grant. After graduating from UD in 2014 with a doctorate in civil and environmental engineering, Mieras joined the faculty at University of North Carolina Wilmington in the Coastal Engineering program.

It was while Mieras was at UD for his doctorate and subsequent postdoc position at the Naval Research Laboratory that he and Puleo collaborated on the design and concept of a conductivity concentration profiler (CCPflex) to quantify sediment concentration in the nearbed mobilized layer. Together, they also worked on a joint project with colleagues at the University of Grenoble, France, investigating how various flow strengths and sediment size affected the sensor in comparison to an alternative approach. Ultimately, the goal is to create a sensor with the capability to take three different measurements at once, leading to more accurate data. Further research and testing will be carried out in large-scale wave flumes and at coastal sites associated with other ongoing research and in coordination with the U.S. Army Corps of Engineers.

Mieras gives credit to Puleo for instilling in him the qualities that make a good adviser and mentor. He said he tries to emulate his former professor now that he is a professor himself. Looking to the future, he is also pleased with how the camaraderie and collaboration he has experienced will help others in the field. As work on the sensor continues, it will no doubt create further connections. 

“Once we've developed this piece of equipment, it will be housed partially at UNCW and partially at UD, and so we now will be the place that any researchers who are studying sand transport or any sort of marine or ocean processes, which require this piece of equipment, they will have to now contact us,” Mieras said. “It's going to start building a network of other researchers, in the U.S. and internationally.”

Over the next three years, Mieras and Puleo will build the sensor. Along the way, undergraduate students will also be involved in the prototype testing and assembly stages. So, while this research is on the cutting-edge already, it will also continue to look ahead, educating the next generation of applied instrumentation users and designers.

The awards are also the result of much research and going back to the drawing board. While Puleo’s project aims to fine tune a new piece of technology, it builds upon past iterations. As a sediment transport expert — or someone who studies the way sand and materials move under different conditions — Puleo saw a need for a sensor that could make multiple measurements at once. While an early sensor that Puleo and his team built had limitations, hard work has helped them move closer to the best option.

“Our sensors will help push the science forward,” Puleo said.