Coastal Storm Modeling System (CoSMoS)

The Coastal Storm Modeling System (CoSMoS) is a numerical modeling system used to predict coastal flooding due to climate change-driven sea-level rise and storms. CoSMos provides explicit, deterministic modeling of all the relevant physics (e.g., tides, waves, surge) of a coastal storm scaled down to local flood resolution projections. The system provides coastal planners and emergency managers with hazard information to inform coastal management, mitigate physical damage, and enhance public safety. CoSMoS was developed for hindcasting, operational applications, and future climate scenarios. The system was initially developed and tested for the coast of Southern California but is not site-specific and can be used for any sandy and/or cliff-backed coasts.

CoSMoS makes detailed, meter-scale predictions of coastal flooding, erosion, and shoreline change over large geographic scales using multiple levels of models. Results of recent Global Climate Models are run through a global wave model, producing wave conditions for the U.S. West Coast. Numerical modeling tools downscale these wave, tide, and storm surge conditions to the local level. These local coastal water levels are then projected onto a two meter Digital Elevation Model to estimate flooding extent.

CoSMoS offers a full range of sea-level rise and coastal storm scenarios. Users can choose from 50 combinations of storms and sea-level rise to visualize flooding, wave height, current strength, and event-based shoreline change for a given event. The model also includes ecology, land use, and infrastructure attributes.
CoSMoS currently has three existing applications, with three additional applications in development.

  • CoSMoS 1.0 Southern California: CoSMoS helped test an extreme winter scenario  and has performed two hindcasts for the January 2010 El Nino and 2005 Newport Harbor Flood, allowing model validation assessment. These hindcasts have helped inform future sea-level rise scenarios and improve flood predictions.
  • CoSMoS 2.0 North-central California (outer coast): CoSMoS produced a suite of coastal flooding projections for over 40 combinations of projected sea-level rise and storm conditions from Bodega Bay to Half Moon Bay. These results are published on interactive maps which overlay infrastructure and ecosystem vulnerabilities.
  • CoSMoS 2.1 San Francisco Bay: CoSMoS is being directly used in climate change vulnerability studies for Marin County and San Mateo County.
  • CoSMoS 2.2 Pt. Arena and Russian River: This application is in progress, with preliminary data available in early 2016. CoSMoS will be implemented north of Bodega Bay to Pt. Arena, focused on several watershed areas such as the Gualala and Russian rivers.
  • CoSMoS 3.0 Southern California: This application is in progress, with preliminary data available in fall 2015. CoSMoS information will be used by several municipalities to update their Local Coastal Plans to incorporate climate change impacts as mandated by California.
  • Operational CoSMoS model - San Francisco Bay Coastal Flood Forecast pilot project: This application is in development. The Coastal Flood Forecast project aims to connect watershed flood projections with CoSMoS’ ocean-based flood projections for integrated coastal-flood forecasts up to 72 hours before a storm.


CoSMoS was developed by USGS and Netherlands-based research institute Deltares.

In order to maintain access to this website, we are linking to an archived version of the website saved on September 8, 2016. The original link can be found here:


Related Organizations:


Resource Category:

Resource Types:

  • Modeling tool

States Affected:


Go To Resource