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Pinpointing Beach Erosion Through Satellite Imaging

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The Metropolitan Beaches Project, run by Dr. Brett Sanders, professor of civil and environmental engineering at UCI, aims to raise awareness of beach erosion by focusing on observation and modeling of changes in beach trends. 

In an interview with the New University, third year civil engineering and urban planning student researcher Victoria Lee explained a specific satellite approach to coastal monitoring and modeling. Daniel Kahl, a graduate student researcher at the Henry Samueli School of Engineering, leads the undergraduate student team Lee is on.

During winter quarter 2021, Kahl’s team began their first accuracy assessment project to determine how accurate the researchers’ collective waterline measurements were. In order to prevent bias, each of the researchers was individually tasked with collecting data on the same portion of the beach. For the Metropolitan Beaches project, the researchers used “a big map application to get satellite imagery … [in order to] make points on the map,” Lee said.

When observing the satellite imagery, researchers like Lee will mark the point where the beach waterline is creating transects, or lines that transverse across or in a section. 

Laguna Beach Satellite Imagery with map application overlay. This image belongs to Metropolitan Beaches Project, Group 2.

Recently, Lee’s group created a presentation for an accuracy assessment report on Laguna Beach that compared the waterlines in 1970 and 1992. 

During this process, Kahl’s team realized how bias arises from each researcher’s subjective interpretation of where the waterline should be. After analyzing everyone’s data, Kahl’s team innovated a solution by creating a standard measurement of the waterline to ensure consistent data collection. 

In the spring quarter 2021, the 100×100 project began, which entails marking beaches on the coast of Southern California and comparing the markings with beach images from the past 100 years. 

Researchers mark “every 10 years from the past 100 years, every 100 meters. That’s why it’s called the 100×100,” Lee said.  

Kahl split the team into different groups, each with three researchers to ensure an adequate sample size to prevent bias. Each group was assigned to a specific portion of the beach to mark changes in the waterline over the last 100 years.

According to Lee, researchers faced difficulty when attempting to observe the waterline on the beach when satellite imagery is blurry. Today, technology development allows for clear and detailed images; however, in the early to mid-1900s, this was not always the case. 

“We don’t have very sharp images. In the developing process, [the satellite images were] overexposed, and so it’s really hard to see [the waterline] sometimes,” Lee said. 

In Lee’s experience of collecting data of a specific section of Dana Point, pocket beaches — small areas in between cliffs along the coast — are a particular region among the Orange County coasts that are severely suffering from beach erosion. Not only are pocket beaches decreasing significantly, but “they’re almost gone,” Lee said. 

The reason why researchers at the Metropolitan Beaches Project are measuring the width of the beaches is to observe how they change over time. By examining the trends, such as beach loss or erosion, Sanders’ teams are providing vital information concerning the impacts of climate change and global warming on metropolitan beaches. 

When asked how people can fix beach erosion, Lee said it is not exactly a preventable issue; however, “if we were a little kinder to our planet and the environment, these changes would slow dramatically.”

To read more about the UCI Flood Lab or Metropolitan Beaches Project, visit their website here.

Natalie Ringdahl is a STEM Intern for the spring 2022 quarter. She can be reached at nringdah@uci.edu.