Sea Cliff Change on the Santa Barbara Coastline

About

Date: 

06/05/2017 (All day)

PI/Speaker: 

Paul Alessio

 

Original report written by Paul Alessio. Interview and editing by Bailee Abell.

For the 70 percent of California coastline made up of sea cliffs, environmental changes such as erosion are inevitable. Large portions of these sea cliffs are home to important infrastructure—and University of California, Santa Barbara, is one of them. Several homes and buildings within the campus and Isla Vista community—particularly those near sea cliff edges at Campus Point and Del Playa Drive—are at risk of damage caused by erosion. Students like Paul Alessio are looking to understand how sea cliff change occurs in order to predict the impact of rising sea levels on the coastal landforms.

“A lot of people in Santa Barbara are connected with the coast,” Alessio said, noting the importance of his research to the local community. “Most people see it almost every day, and the coastline here is such a dynamic environment that it’s easy to notice the changes that occur, even on a daily timescale...This project, and my research interests in general, are at the intersection of most of my passions and hobbies—backpacking, surfing, conservation, exploring new landscapes, and landscape evolution. I’m from San Diego, CA, and I have been going to deserts, mountains, and beaches my whole life.”

Prior to this project, Alessio studied landslides at the United States Geological Survey working master’s student. As his landslide project came to an end, a “godzilla” El Niño

 was forecast to hit the West Coast. His advisor, Ed Keller, wanted to measure cliff erosion over the course of these El Niño events.  Alessio saw a good research opportunity—and working on the beach sparked his interest—so he gave his best effort to make the project come to life. “Fast forward a year and a half, [and add] a ton of stress, confusion, and figuring out how to operate equipment [and] computer programs, and here I am, still scanning cliffs and analyzing all the data from last year because I think it’s interesting.”

Currently, Alessio and his team aim to determine the individual effects of waves, water level, rainfall, and sand levels on cliff erosion rates and patterns. This information will help develop more efficient models for sea cliff retreat, allowing researchers to more accurately predict where the cliff edge will be within the next decades.

“The rate of sea cliff erosion is expected to accelerate with sea level rise, as well as with stronger and more frequent storms and El Niño events,” Alessio said, “but we do not have a good estimate of how much the rate will increase.”

During the 2016 El Niño events, the wave energy flux along the Southern California coast was three times higher than the average level. With intense waves came increased erosion at the base of the sea cliffs, making the tops of the cliffs less stable. With this in mind, Alessio and his team investigated six sites along the Santa Barbara coast to determine the influence of shoreline characteristics and wave dynamics. From November 2015 until September 2016, they scanned the coastline and sea levels during times that exhibited pre-El Niño conditions, post-El Niño storms, and post-El Niño conditions. They found that during the winter months—when the coast experienced greater amounts of high-energy waves and storms—local sea levels increased by up to 20 cm.

“Our hypothesis for this observation is that the waves carrying sand and stones act as ‘tools’ to erode the sea cliff,” he said. Alessio and his team call this the “shotgun hypothesis”—the act of a wave crashing into a cliff and carrying rock debris with it is similar to the sensation that would occur if the cliff was blasted by a shotgun.

Some researchers assume there is a correlation between wave energy and erosion rates, such that wave energy causes erosion at the base of sea cliffs. However, after evaluating the sea cliffs at Lagoon Road at UCSB, the Coal Oil Point Reserve, and on the coast of Isla Vista, Alessio’s research suggested that waves primarily act to remove already eroded particles at the base of sea cliffs. Because of this, he found that the midsection of each sea cliff lost the most material during high-energy wave conditions, and the width of the beach helped protect cliffs from erosion.

As relevant as his research is to the Santa Barbara community, it is also important to Alessio’s own life and beliefs. “For me, I place a lot of value in understanding the community of living organisms and the physical environment around it,” he said. “I believe that the better we understand it, the more likely it is that we get the most out of it...Regardless of what your values are, proper planning and understanding of the natural system, including our impacts, allows for a much better experience and preservation of our environment.”

Much of Alessio’s project was made possible with funding from the ERI fellowship grant, as well as California Sea Grant and the Coastal Fund at UCSB. “I enjoy what I’m working on and the time spent in the Earth Science Department and hope that research continues to be a lifelong passion where I can continue to contribute to the knowledge of the scientific community as well as help inform decisions in how we steward our land.”