CoSMoS is a dynamic modeling approach that allows for detailed projections of coastal flooding due to both future sea level change and extreme storms, integrated with long-term coastal evolution (i.e., beach changes and cliff retreat). CoSMoS models all the relevant physics of a coastal storm (e.g., tides, waves, and storm surge), and results are scaled down to local flood projections for use in community-level coastal planning and risk-reduction. Wind and pressure from global climate models are used to project coastal storm impacts under changing climatic conditions, rather than relying on historical storm records. Resulting hazard maps are available for multiple storm scenarios under a consistent suite of sea-level rise scenarios. These options allow users to manage and meet their own planning time horizons and specify degrees of risk tolerance, in line with California Sea Level Rise Guidance (2024).

The recently released projected flood hazard data for Mendocino County culminates over 12 years of dedicated work on understanding and modeling coastal flooding hazards in California and supporting end-user applications. Products have been used extensively for coastal resilience and risk reduction by approximately 200 organizations, including local, state, and federal agencies. In the latest (2023) California Coastal Adaptation Needs Assessment, coastal practitioners identified CoSMoS as their preferred resource for authoritative future coastal hazards and flooding information. Led by the USGS Pacific Coastal and Marine Science Center, the California effort involved over 200,000 hours (or 22 years) of computer simulations, use of USGS and NASA High Performance Computers, and collaborative work with a host of partners for modeling, web tool development, and end-user outreach and engagement. Key partners included Deltares, USGS Earth Resources Observations and Science, Point Blue Conservation Science, the USGS Western Geographic Science Center, and funding support from the State of California.

Products can be easily viewed and accessed on Our Coast, Our Future and via the USGS Hazard Exposure Reporting and Analytics (HERA) web tool. Data are also downloadable for technical use from ScienceBase, where accompanying shoreline-change, cliff-retreat, and groundwater hazard data are also available.