The Coastal Storm Modeling System

Science Center Objects

The Coastal Storm Modeling System (CoSMoS) provides emergency responders and coastal planners with critical storm-hazard information such as flood extent, flood depth, duration of flooding, wave height, and currents that can be used to increase public safety, mitigate physical damages, and more effectively manage complex coastal settings. The CMHRP initially developed CoSMoS in collaboration with Deltares, and later in partnership with the National Oceanic and Atmospheric Administration (NOAA), the National Park Service, and nongovernmental organizations (NGOs).

View from sky of a city, bay, and nearby island with visible features like buildings, airport, and bridge, with labels.

Example of CoSMoS projection displayed in the Our Coast, Our Future (OCOF) online tool.

Series of diagrams with arrows from left to right, how data visualization tool goes from a global to regional to local scale.

CoSMoS’s approach to projecting flood hazards: global winds, waves, tides, and anomalous water levels are scaled down to the local scale for  projecting nearshore wave heights, flooding, and shoreline change, including beach erosion and cliff failures.

In contrast to simple models that only use data on tides and sea level rise to calculate the possible extent of coastal flooding, CoSMoS includes the effects of possible future storms and synthesizes global wave, tide, and atmospheric conditions, as well as detailed local elevation data, to more accurately project flood hazards for the twenty-first century. The range of possible CoSMoS simulations includes more than 40 combinations of storm conditions (i.e., average daily, 1-year, 20-year, and 100-year) and projected sea level rise (from 0 m to 5 m).

Map shows a coastal city with an airport and how, during a large storm, ocean water would flood around city features.

Example of CoSMoS projected flooding extents for a 1.5 meter sea level rise in combination with possible 100 year return period coastal storms. Credit: Our Coast, Our Future (OCOF)

The results from CoSMoS are integrated with Geographic Information System (GIS) platforms to include social and resource data. Storm hazard projections from CoSMoS are available in easy-to-use online decision support tools (Our Coast Our Future [OCOF] and Hazard Exposure Reporting Analytics [HERA]). Data can be extracted and used in conjunction with user-specific geospatial data, allowing the CMHRP and stakeholders to make assessments that align with multiple users’ interests.

NGOs and other partners use social media and outreach at workshops and conferences to connect potential users to the OCOF and HERA tools. CoSMoS results are already making significant impacts on critical coastal management discussions in California. As one example, numerous California municipalities and counties are now conducting focused vulnerability and climate adaptation studies for at-risk areas identified with CoSMoS.

Additionally, NGOs involved with OCOF have coordinated massive citizen-science data collection events to document the extent of flooding associated with extreme high tides. The California King Tides program provides extensive observational data and samples to validate and improve model systems used in flood projections. This engagement further enhances support and value of this project with the public, as well as supporting CMHRP’s data collection goals.

Screenshot from interactive mapping tool that displays projections of flooding given sea level rise and other factors.

Projections of future coastal flooding by CoSMoS indicate that the city of Pacifica is among the most vulnerable cities to climate change on the entire outer coast of California. This map from Our Coast, Our Future shows the projected future flooding at Pacifica considering 1.25 m of sea level rise with the added impacts of an extreme storm. Credit: Our Coast, Our Future (OCOF)

Future Directions

Public and governmental demand for implementation of CoSMoS has expanded to include the entire California coast as well as Puget Sound in Washington, and possibilities for the remainder of the U.S. West Coast, Alaska, and U.S. Pacific Islands. With each implementation, research on the underlying models, processes, and future storm events leads to refinement of the model system. Specific areas of research include accounting for regional variation in storm conditions, better inclusion of river discharges and runoff during a storm, long-term changes (century scale) in sandy shorelines and cliff erosion, groundwater impacts, and socioeconomic exposure.

CoSMoS is being actively developed for use in operational forecasting through a partnership with NOAA’s National Weather Service, a Federal agency well versed in providing real-time critical hazard information to the public. In a short-term forecasting mode, CoSMoS ocean-based coastal flood projections will be fused with a watershed-based flood model for a comprehensive coastal flood forecast up to 72 hours in advance of an approaching storm.

CoSMoS projections of coastal landscape changes are being used in numerous follow-on social and ecosystem studies: numerous projects along the California coast are using CoSMoS results to evaluate physical and economic vulnerabilities associated with sea level rise and potentially changing storm conditions.

Water splashes onto a cement waterfront walkway through chain link fencing.

Unusually high tides, sometimes called "king tides," offer a preview of coastal flooding likely to result from rising sea level. In this photograph, taken during a king tide on February 17, 2011, waves overtop Pier 14 in San Francisco, California. Credit: Mike Schweizer