Central California CoSMoS v3.1 projections of coastal cliff retreat due to 21st century sea-level rise

This dataset contains spatial projections of coastal cliff retreat (and associated uncertainty) for future scenarios of sea-level rise (SLR) in Central California. Present-day cliff-edge positions used as the baseline for projections are also included. Projections were made using numerical models and field observations such as historical cliff retreat rate, nearshore slope, coastal cliff height, and mean annual wave power, as part of Coastal Storm Modeling System (CoSMoS). Read metadata and references carefully. Details: Cliff-retreat position projections and associated uncertainties are for scenarios of 0.25, 0.5, 0.75, 0.92, 1, 1.25, 1.5, 1.75, 2, 2.5, 3.0 and 5 meters of SLR. Projections were made at CoSMoS cross-shore transects (CST) spaced 100-200 m alongshore using a baseline sea-cliff edge from 2016 (included in the dataset). Within the zip file, there are two separate datasets available: 1) one that ignores coastal armoring, such as seawalls and revetments, and allows the cliff to retreat unimpeded (“Do Not Hold the Line”); and 2) another that assumes that current coastal armoring will be maintained and 100% effective at stopping future cliff erosion ("Hold the Line"). An ensemble of four numerical models synthesized from literature were used to make projections. All models relate breaking-wave height and period to cliff rock or unconsolidated sediment erosion. As sea level rises, waves break closer to the sea cliff, more wave energy impacts the cliffs, and cliff erosion rates accelerate. The final projections are a weighted average of all models (weighted by model performance), and the final uncertainties are proportional to 1) underlying uncertainties in the model input data, such as historical cliff retreat rates, and 2) the differences between individual model forecasts at each CST so that uncertainty is larger when the models do not agree. Uncertainty represents the 95% confidence level (two standard deviations about the mean projection). Model behavior also includes wave run-up and wave set-up that raises the water level during big-wave events. Please refer to Limber and others (2018) for more detailed information on the model and data sources.