Lines in the Sand: The Challenges of Beach Width as a Parameter for Coastal Vulnerability

As local coastal management in San Diego begins to develop climate change adaptation plans to address growing coastal vulnerability, beach width, the distance between the shoreline and the landward limit of the backshore, is growingly being cited as a metric for evaluating coastal vulnerability and triggering a more aggressive adaptive response. This is because narrowing beach width could serve as an early warning indicator of long-term beach erosion or permanent beach loss. The beaches may also serve as a buffer against coastal hazards such as king tides, wave energy and sea-level rise for coastal homes, businesses, or infrastructure. This study assessed spatio-temporal trends associated with the natural variability of beach width and identifying deviations from the norm. The analysis was conducted using 8 years(2008-2016) of monthly beach width data collected by the Scripps Institution of Oceanography, from two locations in San Diego – Imperial Beach and North Torrey Pines and compared with quarterly beach surveys at the same locations for the SANDAG Regional Shoreline Monitoring Program. Additionally, this study will highlight the importance of El Niño seasons and beach nourishments on beach width variability, and how these factors might be considered when establishing a beach monitoring approach and setting triggers for implementing an adaptive response.