Sea Level Rise – Coastal Inundation Scenarios

Global models indicate that California will see substantial sea level rise (SLR) during this century. The exact magnitude of the SLR depends on factors including global emissions, the rate at which oceans absorb heat, melting rates and movement of land-based ice sheets, and local coastal land subsidence or uplift. This tool presents a subset of data from 2 of the several SLR models available for California - which were (partially) funded by the Fourth Assessment. These models (CalFloD3D-TFS and CoSMoS) include SLR and storm inundation modeling. With the inclusion of time and physical processes these dynamic models give more realistic inundation simulations than static models would (e.g. bathtub and pathway models).

Users can explore coastal inundation scenarios associated with SLR and a near 100-year storm scenario along the California coast and San Francisco Bay from two different models (CoSMoS and CalFloD3D-TFS) for two time periods, near term (2020–2040) and end of century (2080–2100). The CoSMoS model provides flooding products under different return-interval storms combined with incremental SLR scenarios from 0–3 m (0–9.8 ft). The CalFloD3D-TFS model provides flooding datasets for combinations of 2 primary RCP scenarios, 4 priority climate models, 3 probabilistic SLR (50th, 95th, 99.9th percentiles) values and 5 planning horizons. For this tool, the CoSMoS flooding datasets for the 100-year-return interval and incremental SLR scenarios were cross-walked with the CalFloD3D-TFS datasets for two planning horizons (2020-2040 and 2080-2100) based on maximum water level at the corresponding tide gauge locations during flood events.

The Coastal Storm Modeling System (CoSMoS) is a modeling approach developed by the U.S. Geological Survey that projects coastal flooding and shoreline change (sandy beach change and cliff retreat) due to both SLR and coastal storms driven by climate change. CoSMoS was designed to understand the present-day and future vulnerability of the coast in support of federal and state climate change guidance, local planning, and emergency response. More details on CoSMoS, its use of multiple component models, and additional model outputs from flooding and erosion are available at Our Coast Our Future.

The CalFloD3D-TFS model assesses potential coastal flooding exposure to areas of interest to the Transportation Fuel Sector (TFS) over five 20-year planning horizons and the Fourth Assessment scenarios using a 3Di hydrodynamic model during extremely high sea level events (72 hour storm event). Due to the inclusion of aboveground objects such as buildings and levees, CalFloD-3D depicts detailed land surface details. Details are described in Radke et al., 2018. A statewide dataset at 50 m spatial resolution is the output of the regional scale modeling. A local scale model that uses a 5 m surface model containing more detailed topography, bathymetry, and building footprints is available for some areas along the coastline.