A newly-funded program to accelerate the science behind coastal bluff failures was signed into law this week. The bill, AB 66, will fund enhanced coastal monitoring to better understand the timing of bluff failures and help inform recommendations towards the development of a potential early landslide warning system.
The bill was introduced by Assemblymember Tasha Boerner Horvath, who secured $2.5 million for this three-year study through the state budget. Scientists at Scripps Institution of Oceanography at the University of California San Diego will lead the research on cliff erosion.
Scripps Oceanography coastal geomorphologist Adam Young has been surveying the cliffs in San Diego County for several years using Light Detection and Ranging (LiDAR), a system that scans the cliffs with a laser creating very high resolution three-dimensional spatial maps of the coast. Young’s research aims to better understand coastal change such as the multiple interwoven cliff erosion processes that create cliff instability and trigger gravity-driven failures.
“Each LiDAR survey provides a snapshot in time that we compare to previous surveys, to measure and track erosion over time,” said Young. “We use these surveys combined with other sensors to quantify the erosion processes, identify erosion patterns, and examine stability conditions.”
AB 66 was supported by Boerner Horvath, whose district includes San Diego’s coastal North County, after tragic fatalities in August 2019 when a 30-by-25 sandstone chunk broke loose and unfortunately fell onto three women at Grandview Beach in Encinitas. Critical infrastructure and development, including a key railroad line, are also threatened by actively eroding cliffs.
"With the passage of AB 66, we are one step closer to saving lives along California's coasts," said Horvath. "Bluff collapses are a constant threat to coastal neighborhoods in Northern San Diego County and across the California coast, presenting the risk of fatalities, injuries, and millions of dollars in damage to vital infrastructure."
With funding from this bill, Young and Scripps Oceanography geophysicist Mark Zumberge will aim to gain a better understanding of the processes that lead up to cliff failures. A central goal is to discover if any signature exists that could foretell heightened risk in specific locations. Learning how ground deformations are impacted by tides, large surf, groundwater, and rainfall may help answer the question of whether signals exist that can forecast where and when an increased risk for collapse is developing. This information will be foundational to the development of an early warning system.
Their approach is twofold, involving expanded LiDAR surveys and also new geotechnical monitoring technology. LiDAR surveys will identify where and when cliff failures have occurred, the shape of the cliffs before and after failures, and the size of failure events.
Scripps Oceanography scientists will also install optical-fiber strainmeters at key locations along the cliffs. The strainmeters, a technological advance developed at Scripps Oceanography for seismic research, can measure earth movements at the scale of microns. Additionally, researchers will deploy tiltmeters, the development of which was pioneered by Scripps Oceanography engineers such as Frank Wyatt. Tiltmeters can measure microscopic-scale changes in spatial orientation of masses of earth that potentially can provide predictive capability to public safety entities that monitor slope stability.
“AB 66 will allow the installation of sensors whose capabilities exceed what was available in the past, and in so doing we hope to learn more about what happens before a slope becomes a slide,” said Zumberge.