Coastal Changes and Impacts

Sea-level rise

The accuracy with which coastal topography has been mapped directly affects the reliability and usefulness of elevation-based sea-level rise vulnerability assessments. Recent research has shown that the qualities of the elevation data must be well understood to properly model potential impacts. The cumulative vertical uncertainty has contributions from elevation data error, water level data uncertainties, and vertical datum and transformation uncertainties.

The concepts of minimum sea-level rise increment and minimum planning timeline, important parameters for an elevation-based sea-level rise assessment, are used in recognition of the inherent vertical uncertainty of the underlying data. These concepts were applied to conduct a sea-level rise vulnerability assessment of the Mobile Bay, Alabama, region based on high-quality lidar-derived elevation data. The results that detail the area and associated resources (land cover, population, and infrastructure) vulnerable to a 1.18-m sea-level rise by the year 2010 are reported as a range of values (at the 95% confidence level) to account for the vertical uncertainty in the base data.

Examination of the tabulated statistics about land cover, population, and infrastructure in the minimum and maximum vulnerable areas shows that these resources are not uniformly distributed throughout the overall vulnerable zone. The methods demonstrated in the Mobile Bay analysis provide an example of how to consider and properly account for vertical uncertainty in elevation-based sea-level rise vulnerability assessments, and the advantages of doing so.

Sea-level rise Individual lidar collections used to develop the multi-source digital elevation model used in a Mobile Bay sea-level rise assessment. U.S. Geological Survey image created by Dean Gesch.

Sea-level rise Minimum and maximum extent of the area vulnerable to a 1.18 m sea-level rise (at 95% confidence) within the Mobile Bay, Alabama, region. Dark blue tint indicates the minimum extent of the vulnerable area, and the light blue tint indicates the maximum extent. U.S. Geological Survey image created by Dean Gesch.

Additional information regarding elevation-based sea-level rise assessments is located at

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