Determining an efficient method for measuring coastal currents

Accurate measurements of surface currents are crucial for coastal monitoring, rip current detection, and predicting the path of pollutants. Several methods exist to measure surface currents, some of which are costly and time consuming. 

In a recent paper, researchers from Texas A&M University compared three methods for measuring surface currents over large areas, identifying an ideal method that uses drones and wave-based current mapping. The technique relies on short aerial videos and mathematical analysis of wave patterns to determine a current’s speed and path.

“This has the potential to change the way we measure near-surface velocity fields in the ocean,” said Dr. Scott Socolofsky, a professor and the J. Walter “Deak” Porter ’22 and James W. “Bud” Porter ’51 Chair in the Zachry Department of Civil and Environmental Engineering, and affiliate professor in the Department of Ocean Engineering and Department of Oceanography.

Socolofsky partnered with Dr. Kuang-An Chang, a joint professor in the ocean engineering and civil and environmental engineering departments. They also collaborated with former Ph.D. students Dr. Soo Bum Bae and Dr. Hsing-Yu Huang, who played key roles in this research study. 

Accurately predicting surface currents is particularly beneficial during oil spills or chemical leaks, when emergency responders need reliable data to predict where pollutants will travel. Traditional coastal radar systems used to measure currents over large areas are costly and often fixed in one place, creating a need for a cost-effective mobile and high-resolution solution. 

Researchers evaluated three alternative techniques, including particle tracking and optical flow methods, which attempt to follow the movement of visible features on the water’s surface. Those approaches have been tested previously, but researchers found they were frequently disrupted by breaking waves, glare from the sun, and the need to deploy tracers — floating markers that can be difficult or unsafe to use near shorelines or in contaminated waters.

The third and most ideal method uses a wave-based technique to analyze wave shifts as they move with or against ocean currents. By using the Doppler effect — a change in wave frequency caused by underlying water movement — researchers can accurately calculate surface current velocity from video footage alone.

The videos are captured using a consumer-grade drone flying over the area of interest for about 30 seconds. Software then processes the wave patterns to estimate current speed and direction.

“This approach offers several advantages. It requires no physical contact with the water and no tracer materials, making it safer and easier to deploy,” said Chang. 

“It also works in most lighting conditions and can cover wide areas in a short amount of time,” added Socolofsky. “Most importantly, it significantly reduces costs. With this method, you can get meaningful current measurements using a drone that costs around $1,000.”

The determination of an ideal method for measuring currents has the potential for national benefits. The National Oceanic and Atmospheric Administration (NOAA) forecasts currents to predict the movement of pollutants during oil spill response efforts, where rapid assessments can inform containment and cleanup strategies. By implementing the most effective method of current measuring, pollutant tracking becomes more accurate. 

Socolofsky and Chang are working with current graduate students Vivek Bheeroo and Mu-Jung Lee, as well as undergraduate students from several disciplines, to further this research. Future work aims to expand the technique’s capabilities to include nighttime measurements using infrared cameras, detection of oil on beaches, and analysis of ship wakes and the stability of coastal infrastructure. Researchers also hope to adapt the approach for use near ports, offshore platforms and sensitive ecosystems.

By Alyssa Schaechinger, Texas A&M University College of Engineering

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