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U.S. Geological Survey (USGS) scientists, in collaboration with the National Oceanic and Atmospheric Administration (NOAA) and PRBO Conservation Science (formerly Point Reyes Bird Observatory), recently released the beta version of an interactive tool for assessing climate-change impacts along the north-central California coast. The new Climate Impacts Tool, which currently covers the California coastline from Half Moon Bay to Bodega Bay (see map), was posted on February 20, 2013. The new tool is part of Our Coast Our Future (OCOF), a project that seeks to provide science-based decision-support tools to natural-resource managers, local governments, and others in the San Francisco Bay region to help them understand, visualize, and anticipate local coastal climate-change impacts within the bay and along the outer coast.

The technical underpinning of the new Climate Impacts Tool is the Coastal Storm Modeling System (CoSMoS), a numerical modeling system developed by the USGS and Netherlands-based research institute Deltares to predict coastal flooding caused by both sea-level rise and storms driven by climate change.

Sea level along the California coast is expected to rise by as much as 1.7 meters (approximately 6 feet) by 2100 (National Research Council, 2012. Winter storms can elevate coastal water levels by an additional 5 meters (approximately 16 feet) or more, primarily because of large waves and storm surge (rise in water level caused by low atmospheric pressure and wind). The additional water-level rise caused by severe storms is addressed in the CoSMoS modeling system, enabling its users to more accurately assess the future vulnerability of coastlines to flooding caused by climate change.

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CoSMoS modeling begins with feeding the results of the latest global climate models into a global wave model to predict wave conditions for the U.S. west coast through 2100. These offshore wave conditions, combined with predicted tides and storm surge, are scaled down to the local level with state-of-the-art numerical modeling tools to predict coastal water levels. The water levels are then projected onto a digital elevation model (DEM) with a 2-meter grid (a grid consisting of squares 2 meters on a side, with each square assigned an elevation value). DEMs, like the more familiar topographic maps, show the shape and elevation of the ocean floor and land surface; projecting predicted water levels onto coastal DEMs can be used to estimate the likely extent of flooding. For the north-central California coast, CoSMoS has performed this exercise across the full plausible range of anticipated sea-level rise and storm conditions predicted by the global climate models.

The USGS CoSMoS team includes project manager Patrick Barnard (who is also co-principal investigator, along with Grant Ballard of PRBO Conservation Science, on the Our Coast Our Future project), lead modeler/coastal engineer Li Erikson, geologist Amy Foxgrover, and oceanographer Andy O'Neill. Deltares collaborators include Maarten van Ormondt and Edwin Elias.

The CoSMoS team is currently expanding the modeling system to support coastal-management decisions along shorelines in San Francisco Bay and southern California. CoSMoS not only can serve as a long-term planning tool, but—when extreme storms are approaching—is capable of serving as a real-time warning system for emergency managers, lifeline operators, and resource managers.

Learn more about CoSMoS in “The Framework of a Coastal Hazards Model—A Tool for Predicting the Future Impact of Severe Storms” (USGS Open-File Report 2009–1073) or contact Patrick Barnard. Learn more about Our Coast Our Future.