Scientists capture highly accurate dune changes in response to storms

As hurricane season kicks off, scientists continue to keep an eye on how coastal dunes change in response to landfalling hurricanes and storms that pass offshore. A team led by Peter Adams, Ph.D., associate professor in the Department of Geological Sciences and lead for the CCS Geospatial Group, is measuring how these processes change the coast on the surface and underwater.

Justin Shawler (L), a research physical scientist from the U.S. Army Research and Development Center, and Associate Professor Peter Adams discuss the coquina rock, which extensive deposits of comprise the Anastasia Formation in Florida and is very common to Adams’ research site in St. Augustine. Sedimentary rocks like coquina give researchers insight into past environments and processes at Earth’s surface. (Photo credit: Orlando Cordero)

“The inlet at Matanzas near St. Augustine is a very active, dynamic feature,” said Adams. “The changes that are occurring as a result of storms or seasonal patterns in different currents govern how the water moves into and out of the inlet and how much sediment it draws. If there is a big storm and it takes a big bite out of the dunes and drags that material offshore, we need to know if the material is being removed from that sand-sharing system between dunes and offshore bars.”

Adams’ team measures the movement and changes of a dune, such as how much a dune moved back or how much the beach’s surface lowered, using Regional Time Kinematic (RTK) Global Navigation Satellite Systems (GNSS). RTK-GNSS involves communication between satellites, a base station and a rover to determine exact position data with centimeter-level accuracy. (Photo credit: Peter Adams)

This work to understand how dunes grow, adjust and stabilize, part of the Engineering With Nature project, is critical for guiding dune restoration and for the protection of coastal communities. Adams and his team aim to understand how physical processes like waves and currents shape landscape features such as dunes, beaches and inlets. While directly observing how these systems are changing is informative, advancements in technology increase the ease and cost-effectiveness associated with collecting data.

To cover a large area, the team utilizes structure from motion photogrammetry, which creates three dimensional models using a series of photos captured by a drone. With about a half-hour flight back and forth along the coast and processing on a computer, the team can generate a topographic map much quicker than a walk or drive on the beach to collect spatial measurements. The orientation of the drone and location where it captured each photo along South Ponte Vedra Beach can be seen at the top of the graphic above. (Photo credit: Andrew Ortega)

This work is complemented by modeling done by Maitane Olabarrieta, Ph.D., an associate professor in the Department of Civil and Coastal Engineering. These models can mimic the work done in the field and provide insight into areas that the team is not measuring, as well as ideas for locations to deploy instruments.

The team measures the depth of the seafloor using sound: With single beam echo sounding bathymetric mapping, a sound signal travels and bounces off the seafloor and other underwater features, creating a profile of the seafloor through its travel time in different areas. (Photo credit: Ollerhead and Associates, LTD)

“What’s really helpful about these advances in technology is that it allows us to take a broad-scale opening look at an area and quickly identify where we should be focused,” said Adams. “We used to have a tradeoff, either you could map a broad-scale area with low resolution, or you could map a small area with high resolution. Now, the detail is coming along with the broad range simultaneously.”

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By Megan Sam

June 26, 2023