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Pacific Coastal and Marine Science Center

Coastal Processes

Puget Sound Coastal Storm Modeling System (PS-CoSMoS)

Google Earth false color satellite image of the study area.

Above: Google Earth false color satellite image of the Puget Sound study area. [Larger version]

The USGS Coastal Storm Modeling System (CoSMoS) provides detailed predictions of coastal flooding due to future sea-level rise, storms, and river flooding driven by climate change. The CoSMoS model is currently available for most of the California coast and is now being expanded to support the 4.5 million coastal residents of the Puget Sound region, with emphasis on the communities bordering the sound.

This expansion to Puget Sound was born out of a strong collaboration with the Environmental Protection Agency (EPA), in addition to numerous other partners throughout the region with whom USGS has worked over the past several decades. The goal of this project is to provide consistent, robust, and authoritative sea-level rise and storm-impact projections at the local planning scale for the full range of plausible 21st-century climate scenarios along the entire Puget Sound shoreline. This FAQ (1.5 MB pdf) provides some answers to initial questions about CoSMoS.

An initial stakeholder outreach and engagement workshop was held on September 20, 2017. Representatives from USGS provided background on Puget Sound CoSMoS and some of the initial pilot work in the region. The links to the presentations are available here:

These presentations were followed by break-out and group discussion on how Puget Sound CoSMoS, through continued partnership with ongoing – and potentially new - collaborations, can support regional coastal planning efforts. If you are interested in learning more, would like to discuss your work in the region, or have thoughts for a potential collaboration, please contact Bill Labiosa.

Regional Partnerships and Collaborations

PS-CoSMoS project builds on existing and ongoing work in the region. Notably, USGS is a partner of the Washington Coastal Hazards Resilience Network, a three-year effort to rapidly increase the state’s capacity to prepare for natural hazards that threaten the coast. Through this network, researchers from USGS developed an initial phase of CoSMoS wave modeling for Puget Sound, leading to key partnerships with EPA, the Washington State Department of Ecology, and place-based organizations (e.g., the University of Washington Climate Impacts Group and Washington Sea Grant), among many others. Similarly, USGS researchers are also involved in work with several of the Puget Sound tribes (e.g., the Swinomish Indian Tribal Community). For instance, a March 2016 flood event impacted the Swinomish Reservation. Working with tribal members, the USGS team was able to use this flood event to validate detailed onshore flooding predictions.

A series of three aerial photographs showing the CoSMoS forecasted extent of flooding across the western Swinomish Reservation compared to the actual location of maximum flooding, depicted by the black line, in March 2016.

Above: Photographs show the CoSMoS forecasted extent of flooding (blue) across the western Swinomish Reservation compared to the actual extent of maximum flooding (black line) in March 2016. This helped to validate the accuracy of the USGS CoSMoS model. The projections are made by the USGS and overlaid on a 2011 photograph credited to the National Agricultural Insurance Program (public domain). [Larger version]

PS-CoSMoS aims to provide information to federal, state, tribal, and local agencies seeking to better manage natural hazards, improve salmon, shellfish, and other coastal ecosystems, and plan for an increase in population and pronounced climate change across the basin by mid-century. We continue to develop relationships with other agencies so PS-CoSMoS can be customized to most effectively support a variety of planning needs across Puget Sound’s approximately 4,200 kilometers (2,600 miles) of vulnerable coastline. A standardized set of PS-CoSMoS outputs enable decision-makers to more confidently plan, prioritize, and implement adaptive-management strategies to protect coastal and floodplain communities, ports, and harbors; infrastructure including roads and rail lines; and river-delta and other coastal habitats. In short, PS-CoSMoS will provide important tools to assess and manage coastal-flooding risks to the valuable societal assets and natural resources in Puget Sound.

About CoSMoS

The Coastal Storm Modeling System (CoSMoS) is a dynamic modeling approach that has been developed by the USGS in order to allow more detailed predictions of coastal flooding due to both future sea level rise and storms. It is integrated with long-term coastal evolution (i.e., beach changes and cliff 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 historical 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 [with a close-to 100-percent chance of happening in a given year], 20-year storm [5-percent chance] and 100-year storm [1-percent chance]) 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. These options allow users to manage and meet their own planning horizons and specify degrees of risk tolerance.

CoSMoS will be a valuable resource and addition to the data available and the partnerships already established in the Puget Sound region. Some of the unique components of CoSMoS include:

  • Explicit, deterministic modeling of all the relevant physics (e.g., tides, waves, surge) of a coastal storm scaled down to local flood resolution projections
  • Driven by global climate models, waves are modeled at the global scale, and then dynamically downscaled, along with regional additions of wind, atmospheric pressure, tides, and sea-level rise, to produce hazard projections for managers
  • Scenarios feature the full spectrum of sea-level rise (0 to 2 meter, 5 meters) and coastal storms (daily conditions to 100-year storm) to meet every possible management planning horizon and degree of risk tolerance
  • Product tool will allow the user to select, visualize, and download the flooding depth, extent, and uncertainty associated with each event, in addition to predictions of wave heights, current strength, and ecosystem impacts for 40 combinations of sea-level rise and storms. The tool will provide seamless integration with databases of socioeconomic, ecologic, land use, and infrastructure projections that allow decision-makers to easily analyze likely impacts to prioritize and implement adaptive management strategies.

CoSMoS modeling results have been used by a large number of federal and state partners as well as local communities throughout California. Projections are currently available for much of the California coast (north-central coast (Half Moon Bay to Point Arena), San Francisco Bay, and southern California) with the goal of completing the entire California coastline by the end of 2019. 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.

Example of CoSMoS model output for San Diego showing duration of flooding.

Above: Example of HERA analysis for San Diego. HERA viewer: [Larger version]

Hazard Exposure Reporting and Analytics (HERA)

To support coastal communities in their planning, the CoSMoS team has partnered with 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 scenario. This partnership of expertise in the science of coastal processes and the science of hazard risk and vulnerability allowed the creation of an interactive website application that helps improve awareness and planning efforts regarding socioeconomic exposure to climate-change-related coastal hazards.

For more information

Eric Grossman:
Bill Labiosa:
Patrick Barnard:


Inundated areas shown should not be used for navigation, regulatory, permitting, or other legal purposes. The U.S. Geological Survey provides these data “as is” for a quick reference, emergency planning tool but assumes no legal liability or responsibility resulting from the use of this information.

The suggestions and illustrations included in these images are intended to improve coastal-flood awareness and preparedness; however, they do not guarantee the safety of an individual or structure. The contributors and sponsors of this product do not assume liability for any injury, death, property damage, or other effects of coastal flooding.

Use of trade names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.


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