Coastal Flooding & Solutions, Workshop Case Studies

Puget Sound Coastal Storm Modeling System (PS-CoSMoS)

Location: Salish Sea - Washington State, British Columbia, Canada

Submitted By: Eric Grossman - US Geological Survey

Project URLs:

Project Description

The Puget Sound Coastal Modeling System (PS-CoSMoS) is a coastal flooding model developed to evaluate impending hazards associated with sea level rise and climate change effects to river floods, storms and coastal groundwater in the Salish Sea. Compound flood hazard is computed across the region at 1m resolution to inform coastal planning efforts into the next century. The model is forced with spatiotemporally varying fields derived from dynamically downscaled global climate models at 12km spatial and hourly temporal resolution accounting for wind speed biases observed at higher resolution (2.5 km and site observations) to improve wind and consequent wave estimates in narrow bays and channels. Coastal water levels, waves, sea level rise and stream flows then drive a computationally rapid 2D flood solver that calculates flood extents, depths, duration and velocities of overland flooding and waves to the year 2100 from hundreds of extreme events and to define recurrence and risk estimates for several climate change scenarios. Model results show storm surge is driven primarily by atmospheric pressure anomalies (up to 45cm), outer shelf wind and current dynamics (up to 45cm), large-scale ocean dynamics associated with interannual and oscillations phenomena like the El Nino-Southern Oscillation (up to 20cm), and wind setup generated within the Salish Sea (up to 20cm). Initial results showing the complex spatial vulnerability of Salish Sea estuary to the potential impacts of flooding and waves with accelerating sea level rise are being used to plan adaptation strategies for shoreline management, transportation and water infrastructure, and habitat restoration.

Key Successes

The project is still in its development stage. Outputs for initial geographies within study domain are just being rolled out and are quickly being used for vulnerability assessments and initial adaptation plan scoping and framework development. The results are informing large capital expenditure programs for transportation and water infrastructure planning and coordinated investments in salmon habitat restoration and flood mitigation. The high skill of the regional scale model has enabled us to differentiate the relative contributions of remote and local non-tidal residual processes to flooding important for evaluating potential changes in hazard exposure in the future. Engagement of citizen science volunteers in monitoring storm surge impacts and bluff and beach change through an inter-agency partnership and development of the MyCoast App has led to heightened awareness of impending coastal hazards and interest in science.


Lack of fundamental land surface elevation, water level and wave data

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