The calculated CVI values for GUIS range from 10.33 - 25.0. The mean CVI value is 16.22; the mode and median are 14.14. The standard deviation is 4.39. The 25th, 50th, and 75th percentiles are 13.0, 15.0, and 22.0, respectively.
Figure 9A-B shows a map of the coastal vulnerability index for the Gulf Islands National Seashore. The CVI scores are divided into low, moderate, high, and very high vulnerability categories based on the quartile ranges and visual inspection of the data. CVI values below 13.0 are assigned to the low vulnerability category. Values from 13.0 to 15.0 are considered moderate vulnerability. High vulnerability values lie between 15.1 and 22.0. CVI values above 22.0 are classified as very high vulnerability. Figure 10 shows the percentage of GUIS shoreline in each vulnerability category. Approximately 90 miles (145 km) of shoreline is evaluated in the study area. Of this total, 24 percent of the mapped shoreline is classified as being at very high vulnerability due to future sea-level rise. Eighteen percent is classified as high vulnerability, 36 percent as moderate vulnerability, and 21 percent as low vulnerability.