Surf Quality Impact Assessment—Evaluating Lagoon Restoration Design Alternatives on Surf Quality in Response to Surfing Stakeholders

OUR CHALLENGE

Led by the Resource Conservation District of the Santa Monica Mountains, California State Parks, County of Los Angeles Department of Beaches and Harbors, and Caltrans, the Topanga Lagoon Restoration Project aims to restore estuarine lagoon habitat and realign the Pacific Highway. Integral Consulting was brought in to assess the project’s potential impact on surf quality—a first-of-its-kind evaluation, driven by the concerns of the local surf community.  

OUR APPROACH

To set a foundation for the study, Integral conducted a surf focus group survey to gather information from the surf community. Local surfers were asked about their concerns about the project, use patterns, and access to the break, as well as the best wave conditions to evaluate in the modeling. These conditions were then used to model the existing surf conditions and a simulation of the surf break post-construction, using information about how project alternatives would influence sediment supply and bathymetry. Using three popular wave conditions identified by the focus group, Integral simulated breaking and generated wave paths in XBeach, a high-fidelity wave modeling tool, under four conditions: a) wet conditions, b) drought conditions, c) restoration project alternatives, and d) sea level rise. Our team then used the peel angle (α)—the angle between the wave front and wave path—to measure wave quality. Results showed sea level rise will have the largest impact on future surf quality and any project impacts would be temporary and within the range of natural flood and drought condition variability. The effect of sea level rise illustrated the need to remove an existing revetment as part of the project to avoid future impacts to the surf break. 

OUR IMPACT

After the analysis was presented to the surf community, stakeholders were resurveyed. The new survey showed that perceptions of the project’s impact on surf quality significantly improved and surfers’ concerns about decreased surf quality were largely alleviated. This has resulted in supportive surfer comments on the overall project during the environmental review process. Integrating surf science into coastal management decision–making proved to be effective for objectively assessing impacts of coastal projects and adaptation approaches on surf resources, bridging communication gaps between surf and project stakeholders, and building support for conserving natural recreational amenities.