PS-CoSMoS FAQs

What is CoSMoS?

A numerical modeling system to predict coastal flooding due to sea level rise (SLR), storms, and river flooding driven by climate change.

What is the goal of Puget Sound-CoSMoS?

Delivery of consistent, robust and authoritative SLR and storm impacts projections at the local planning scale for the entire Puget Sound shoreline for the full range of plausible 21st century climate scenarios.

What products will be available?

An interactive web tool and GIS-friendly files for projections of coastal flooding extent, depth, and elevation, as well as maximum waves, currents and ecosystem impacts (e.g., impacts to shellfish beds, forage fish spawning substrate, etc.) for all possible combinations of SLR and coastal storms through 2100. In addition, USGS will produce a web tool translating the physical exposure to coastal hazards for each scenario into socioeconomic impacts, including jurisdictional breakdowns of population exposure and economic impacts.

Who would use this information in Puget Sound?

We have already developed key partnerships with EPA, WA Department of Ecology, numerous tribes, etc., and are looking 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 ~4200 km (2600 mi) of vulnerable coastline. PS-CoSMoS intends to provide information identified as important by federal, state, tribal and local agencies seeking to manage natural hazards, improve salmon and shellfish ecosystems, and plan for an increase in population and pronounced climate change across the basin by mid-century. A standardized set of PS-CoSMoS outputs enable decision-makers to more confidently prioritize and implement adaptive management strategies to protect floodplain inhabitants, coastal ports, harbors and transportation that facilitate the region’s industry and commerce, and low-lying river-deltas and nearshore habitats important to the Nation’s agriculture and salmon populations. CoSMoS is a top-ranked priority for the Puget Sound Partnership (PSP) Action Agenda NTA, would directly support the NEP climate vulnerability assessment (CVA) requirement, and influence the guidance the PSP provides for local entities to perform local CVAs.

What is the timeline for completing PS-CoSMoS?

With initial seed money from within USGS, we are beginning to construct the framework for PS–CoSMoS in 2016, which will build on numerous local and regional field and numerical modeling efforts the USGS and its partners have conducted over the last decade. Funding permitting, the effort is estimated to be concluded in 2020.

Where has CoSMoS been applied and who uses it?

CoSMoS has been applied throughout California, including inside San Francisco Bay. Dozens of city (e.g., Los Angeles, San Diego) and county governments (e.g., Marin County, San Mateo County, Los Angeles County) use CoSMoS as well as large state agencies, such as the California Department of Transportation (Caltrans) and the California Department of Emergency Services (Cal OES), to support their climate impacts and emergency management planning needs.

Why was it developed?

CoSMoS was developed to provide regionally consistent, but locally-relevant storm impacts projections for coastal communities that include the dynamic interaction of all factors that affect coastal hazards presently and due to future climate change. These include not only the long term impacts of SLR but also short-term storm impacts that occur as currents, waves and river flooding affect the shoreline.

Why include storms?

Wave energy reaching the shore increases greatly as water level increases (less friction with the seafloor) and it is estimated that today’s 100-yr coastal flooding event will become a 10-yr event with just 0.3 m (1 ft) of SLR and a 1-yr event with 0.6 m (2 ft) of rise. Sea level is expected to rise up to 1.7 m (5.6 ft) along the U.S. West Coast by 2100, and during winter storms today water levels inside Puget Sound commonly reach 1 m (3.3 ft) above predicted tides and along the outer coast can be elevated by an additional 5 m (16.4 ft) or more due primarily to large waves and storm surge. Without this dynamic component an important aspect of future vulnerability would be missed.

How is the modeling accomplished?

Wind, pressure and temperature projections through 2100 from the latest Global Climate Models (GCMs) are downscaled to the regional level to determine oceanographic conditions during future storm events. Local water levels are determined by modeling the interacting processes of tides, storm surge, waves, and river discharge. The final extent of flooding is based on the flow of water across a 2 m (6.6 ft) Digital Elevation Model (DEM). This is performed for virtually every combination of anticipated SLR and storm condition.

Why use GCMs?

Future storm conditions are likely to evolve in a fashion that is unlike past conditions and is ultimately dependent on the complex interaction between the Earth’s atmosphere and ocean systems, which GCMs simulate. Therefore, the past several decades of oceanographic measurements may not be indicative of the future climate.

What makes CoSMoS unique?

• 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 GCMs, waves are modeled at the global scale, and then dynamically downscaled, along with regional additions of wind, atmospheric pressure, tides and SLR, to produce hazard projections for managers
• Scenarios feature the full spectrum of SLR (0 to 2 m, 5 m) and coastal storms (daily to 100-year return) to meet every possible management planning horizon and degree of risk tolerance
• Product tool allows 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 SLR and storms. The tool provides 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.

Where can I get more information?

• USGS CoSMoS Website
• USGS report - ‘The Framework of a Coastal Hazards Model—A Tool for Predicting the Impact of Severe Storms’
• Our Coast, Our Future - Interactive Map showing flooding impacts for the California