Coastal Storm Modeling System (CoSMoS)

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The Coastal Storm Modeling System (CoSMoS) makes detailed predictions of storm-induced coastal flooding, erosion, and cliff failures over large geographic scales. CoSMoS was developed for hindcast studies, operational applications and future climate scenarios to provide emergency responders and coastal planners with critical storm-hazards information that can be used to increase public safety, mitigate physical damages, and more effectively manage and allocate resources within complex coastal settings.

Application window with parameter settings down the left, map showing results of parameter settings, and legend on right.

Example of CoSMoS model output for San Diego showing duration of flooding. Results displayed on Our Coast, Our Future flood mapper.

The Coastal Storm Modeling System (CoSMoS) is a dynamic modeling approach that has been developed by the United States Geological Survey in order to allow more detailed predictions of coastal flooding due to both future sea-level rise and storms integrated with long-term coastal evolution (i.e., beach changes and cliff/bluff retreat) over large geographic areas (100s of kilometers). CoSMoS models all the relevant physics of a coastal storm (e.g.,tides, waves, and storm surge), which are then scaled down to local flood projections for use in community-level coastal planning and decision-making. Rather than relying on historic storm records, CoSMoS uses wind and pressure from global climate models to project coastal storms under changing climatic conditions during the 21st century. 

Projections of multiple storm scenarios (daily conditions, annual storm, 20-year- and 100-year-return intervals) are provided under a suite of sea-level rise scenarios ranging from 0 to 2 meters (0 to 6.6 feet), along with an extreme 5-meter (16-foot) scenario. This allows users to manage and meet their own planning horizons and specify degrees of risk tolerance.

Artistic map of the west coast showing the names of stretches of coastline for which flooding maps have been made by a computer.

Locations of currently available CoSMoS projections.

CoSMoS projections are currently available for the north-central coast (Half Moon Bay to Pt. Arena)San Francisco Baysouthern California, and the central California coast. The north coast of California will follow with expected completion by the end of 2019. 

All modeling results are available as GIS shapefiles, with accompanying metadata, at USGS ScienceBase-Catalog. CoSMoS information can also be accessed, viewed, and downloaded through the Our Coast, Our Future (OCOF) flood mapper, which provides a user-friendly web-based tool for viewing all model results. OCOF also provides resources and guidance for helping communities navigate and utilize the wealth of information provided by CoSMoS.

To support coastal communities in their planning, the CoSMoS team has partnered with Dr. Nathan Wood (USGS, Western Geographic Science Center) to develop the Hazards Exposure Reporting and Analytics (HERA) application. HERA displays estimates of residents, businesses and infrastructure that could be exposed to CoSMoS flooding projections from each coastal storm and sea level rise scenarios. This partnership of expertise in coastal processes and hazard risk and vulnerability sciences allowed the creation of an interactive website application that helps improve awareness and planning efforts regarding socioeconomic exposure to climate change related coastal hazards.

Although the CoSMoS modeling system was initially developed for use in the high wave-energy environment of the U.S. west coast, CoSMoS is not site-specific and can be utilized on sandy and/or cliff-backed coasts throughout the world. The prototype system developed for the California coast uses the global WAVEWATCH III wave model, the TOPEX/Poseidon satellite altimetry-based global tide model, and atmospheric forcing data from either the U.S. National Weather Service (operational mode) or Global Climate Models (future climate mode) to determine regional wave and water-level boundary conditions. These regional conditions are then dynamically downscaled using a set of nested Delft3D wave (SWAN) and tide (FLOW) models, and are then linked at the coast to river discharge projections, fine-scale estuary models, and along the open coast to closely spaced XBeach (eXtreme Beach) cross-shore profile models. The elevation of the coast is updated for each sea level rise scenario based on the projected long-term evolution of the sandy beaches and cliffs.

Application window with parameter settings down the left, map showing results of parameter settings is on the right.

Example of Hazards Exposure Reporting and Analytics (HERA) analysis for San Diego.

CoSMoS Partners

CoSMoS modeling results have been used by a large number of federal and state partners as well as local communities throughout California. In the San Francisco Bay area and southern California regions, 14 municipalities, including the cities of San Francisco and Los Angeles, and 7 coastal counties (e.g., Marin, San Mateo, San Francisco, and Los Angeles) are actively using CoSMoS for local coastal planning efforts. The major utilities - Pacific Gas & Electric, Southern California Edison, San Diego Gas & Electric and the Los Angeles Department of Water & Power - are similarly using CoSMoS to assess their assets’ vulnerability to sea level rise and coastal storms. CoSMoS also supports a number of state agencies and federal partners; see the whole list on our Partners tab.

Funding for CoSMoS

In addition to extensive internal USGS funding, the CoSMoS team is thankful for the support from California state agencies and communities who have supported and encouraged CoSMoS model development.

A man points to a computer screen displaying a map with colored blocks along a coastline.

Patrick Barnard explains how CoSMoS integrates information from the HERA mapper to understand the social and economic consequences of different flooding scenarios. 

Photo credit: Meaghan Faletti, USGS

Graphic of waves breaking at the ocean surface with lettering below it for the coastal storm modeling system.