Map of Coastal Change-Potential

Calculating the Change-Potential Index

The coastal change-potential index (CPI) employed here is the same as that used in Thieler and Hammar-Klose (1999) and is similar to that used in Gornitz and others (1994), as well as to the sensitivity index employed by Shaw and others (1998). The CPI allows the six variables to be related in a quantifiable manner that expresses the relative change-potential of the coast to physical changes due to future sea-level change. This method yields numerical data that cannot be equated directly with particular physical effects. It does, however, highlight areas where the various effects of sea-level change may be the greatest. Once each section of coastline is assigned a change-potential value for each specific data variable, the coastal change-potential index (CPI) is calculated as the square root of the product of the ranked variables divided by the total number of variables;



where, a = geomorphology, b = shoreline erosion/accretion rate, c = coastal slope, d =relative sea-level rise rate, e = mean significant wave height, and f = mean tide range. The calculated CPI value is then divided into quartile ranges to highlight different change-potentials within the park. The CPI ranges (low - very high) reported here apply specifically to GBNPP, and are not comparable to CPI ranges in other parks where the CPI has been employed (i.e., very high change-potential means the same among parks; it's the numeric values that differ, such that a numeric value that equals very high change-potential in one park may equal moderate change-potential in another). To compare change-potential between coastal parks, the national-scale studies should be used (Thieler and Hammar-Klose, 1999, 2000a, and 2000b). We feel this approach best describes and highlights the coastal change-potential specific to each park.