We are modeling the long-term protective benefits of beach and dune designs in North-Central California, and quantifying the recreation benefits provided by the natural beach area to identify where adaptation investments might have the most cumulative benefits (i.e., maximizing protective, ecological, and recreational benefits), and where there might be trade-offs between local vs. non-local benefits. Results can directly inform prioritization of adaptation investments.
Why We Care
Natural Infrastructure is increasingly used to mitigate coastal flooding, but evaluating the performance and lifespan of natural infrastructure is an ongoing challenge for California and the United States. Coastal decision-makers and engineers lack capable modeling tools and data to evaluate potential benefits and trade-offs of natural infrastructure, especially when considering how features might evolve and degrade over time with rising seas and storms. Further, benefits of natural infrastructure are typically quantified in terms of avoided flood damages to local coastal properties, which can inadvertently prioritize protection for higher income areas. Using non-local benefits — such as beach visitation — would allow for an equity lens to be integrated into cost-benefit assessments, yet are rarely accounted for due to the time and cost requirements of collecting visitor use and origin data.
What We Are Doing
We are modeling the co-evolution of the beach, natural and managed dunes, and flooding under different proposed natural infrastructure projects (i.e., beach nourishment, dune restoration) and inundation scenarios (i.e., future storms and sea-level rise) to evaluate the long-term protective, social, and ecological merits of natural infrastructure in North-Central California. We will adapt the existing U.S. Geological Survey’s Coastal Storm Modeling System shoreline change model [CoSMoS-COAST] to do this.
Using commercially available and anonymous cell phone data, we are also quantifying visitation and origin-based profiles of beachgoers in the study area as a measure of non-local recreation benefits provided by the natural beach area. Currently, the region lacks information on the specific communities that rely on the coast beyond the narrow band of residents in the coastal zone, and these groups therefore have been underrepresented in coastal management and under engaged in the design of adaptation strategies. Relative visitation results will allow us to understand specific locations on beaches within our study area that support higher recreational use compared to others; home origin information allows us to understand geographically where visitors are traveling from to estimate value.
The visitation metrics of four primary study sites will be combined with the modeled estimates of protective benefits (i.e., avoided damages) to identify sites where adaptation investments might have the most cumulative benefits (i.e., maximizing both protective, ecological, and recreational benefits), and where there might be trade-offs between local vs. non-local benefits. These results can directly inform prioritization of adaptation investments, maximizing value to a broad range of beneficiaries.
Study sites are selected to leverage four existing planned natural infrastructure project sites in North-Central California, and we will develop use-case tutorials targeted to coastal managers, engineers, and consultants across California who will be able to readily access and adapt the tools to evaluate design alternatives. These users will be able to answer questions such as: How much sand? Where should it be placed? How often? What are the local flood-protection and non-local co-benefits of this natural infrastructure project?
Benefits of Our Work
This next-generation modeling system and use-case examples from high-urgency projects in North-Central California will be made publicly available for coastal managers and professional engineers as an off-the-shelf model to run scenario-based evaluations of natural infrastructure anywhere on the West Coast. Quantifying non-local recreation usage and benefits provides a more holistic understanding of the benefits and trade-offs of natural infrastructure. Overall, this work will allow for rapid evaluation of a wide range of design alternatives that will enable local coastal managers to more accurately weigh the co-benefits of multiple natural infrastructure projects within a region, helping them determine where to focus adaptation efforts, and ultimately foster innovation in the advancement of natural infrastructure nationwide.
This project is led by Wendy Kordesch at the Greater Farallones Association, in collaboration with Sean Vitousek and Maya Hayden at the U.S. Geological Survey, Nathaniel Merrill (independent contractor), and Max Delaney at the Greater Farallones National Marine Sanctuary, and is funded by the NCCOS Effects of Sea Level Rise (ESLR) Program.