Discussion

Figure 8. Relative Coastal Vulnerability for Padre Island National Seashore. Click on figure for larger image.

The data within the coastal vulnerability index (CVI) show variability at different spatial scales (Figure 8). However, the ranked values for the physical process variables vary little over the extent of the shoreline. The value of the relative sea-level rise variable is constant at very high vulnerability for the entire study area. The significant wave height vulnerability is moderate to low, and the tidal range is very high vulnerability.

Figure 6. Historic Shoreline positions. Click on figure for larger image.

The geologic variables show the most variability and thus have the most influence on the CVI value (Figure 8). Geomorphology in the park includes high vulnerability barrier island shoreline with continuous dune ridges and very high vulnerability washover-dominated or low discontinuous dune areas. Vulnerability assessment based on historical shoreline change trends varies from low to very high (Figure 6 A -C). Regional coastal slope is in the very high vulnerability range for the extent of Padre Island.

The most influential variables in the CVI are geomorphology, shoreline change, and significant wave height; therefore they may be considered the dominant factors controlling how Padre Island will evolve as sea level rises. Geomorphology and significant wave height only vary between high and very high and moderate and low vulnerability, respectively; whereas the shoreline change variable ranges from low to very high.

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