NOAA Office for Coastal Management Sea Level Rise Data: Mapping Confidence

These data were created as part of the National Oceanic and Atmospheric Administration Office for Coastal Management's efforts to create an online mapping viewer depicting potential sea level rise and its associated impacts on the nation's coastal areas. The purpose of the mapping viewer is to provide coastal managers and scientists with a preliminary look at sea level rise (slr) and coastal flooding impacts. The viewer is a screening-level tool that uses nationally consistent data sets and analyses. Data and maps provided can be used at several scales to help gauge trends and prioritize actions for different scenarios. The Sea Level Rise and Coastal Flooding Impacts Viewer may be accessed at: https://www.coast.noaa.gov/slr

These data depict the mapping confidence of the associated Sea Level Rise inundation data, for the sea level rise amount specified. Areas that have a low degree of confidence, or high uncertainty, represent locations that may be mapped correctly (either as inundated or dry) less than 8 out of 10 times. Areas that have a high degree of confidence, or low uncertainty, represent locations that will be correctly mapped (either as inundated or dry) more than 8 out of 10 times or that there is an 80 percent degree of confidence that these areas are correctly mapped.

Areas mapped as dry (no inundation) with a high confidence or low uncertainty are coded as 0.
Areas mapped as dry or wet with a low confidence or high uncertainty are coded as 1.
Areas mapped as wet (inundation) with a high confidence or low uncertainty are coded as 2.

The NOAA Office for Coastal Management has tentatively adopted an 80 percent rank (as either inundated or not inundated) as the zone of relative confidence. The use of 80 percent has no special significance but is a commonly used rule of thumb measure to describe economic systems (Epstein and Axtell, 1996). In short, the method includes the uncertainty in the lidar derived elevation data (root mean square error, or RMSE) and the uncertainty in the modeled tidal surface from the NOAA VDATUM model (RMSE). This uncertainty is combined and mapped to show that the inundation depicted in this data is not really a hard line, but rather a zone with greater and lesser chances of getting wet.

For a detailed description of the confidence level and its computation, please see the Mapping Inundation Uncertainty document available at: https://coast.noaa.gov/data/digitalcoast/pdf/mapping-inundation-uncertainty.pdf