Who's counting: An analysis of beach attendance estimates and methodologies in southern California

Abstract

Accurately assessing visitation patterns at California's beaches is critical; human use data is a primary input into beach assessments that inform staffing, amenities, beach nourishment and the loss of interim use following beach closures. If beach attendance estimates are inaccurate, then these assessments will be similarly inaccurate and could result in the misallocation of public resources to staff and manage coastal lands.This study assesses attendance estimates at selected beaches in Santa Barbara, Ventura, Los Angeles, Orange and San Diego counties by comparing official agency estimates to study estimates informed by periodic counts and sub-sampling techniques. We conclude that official counts often seriously overestimate attendance, in some cases on average by a factor over 5, and that this bias is not random but correlated with a number of factors, including the relative daily attendance load, the size of the beach, and the methodologies employed to produce estimates.The methods agencies use to estimate attendance are often based on old algorithms from unavailable studies that are unsuitable for accurately measuring visitation patterns across user groups. While our results pose serious questions to the accuracy of beach attendance estimates in southern California, there are a number of tangible and economical measures that agencies can take to evaluate and improve their current beach attendance methodologies.