National Assessment of Coastal Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast

Summary

The coastal vulnerability index (C.V.I.) for the Gulf of Mexico coast provides insight into the relative potential of coastal change due to future sea-level rise. The maps and data presented here can be viewed in at least two ways:

• as a base for developing a more complete inventory of variables influencing the coastal vulnerability to future sea-level rise to which other elements can be added as they become available; and
• as an example of the potential for assessing coastal vulnerability to future sea-level rise using objective criteria.

As ranked in this study, coastal geomorphology and tide range are the most important variables in determining the C.V.I. for the Gulf of Mexico coast since both variables reflect very high vulnerabilities along nearly the entire shoreline. Wave height, relative sea-level rise, and coastal slope provide large-scale (50-200 km alongshore) variability to the coastal vulnerability index. Erosion and accretion rates, where complete, contribute the greatest variability to the C.V.I. at short spatial scales. The rates of shoreline change, however, are the most complex and poorly documented variable in this data set. The rates used here are based on a dated, low-resolution data set and thus far corrections have been made only on a preliminary level. To best understand where physical changes may occur, large-scale variables must be clearly and accurately mapped and small-scale variables must be understood on a scale that takes into account their geologic and environmental influences.