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Coastal Vulnerability Assessment of Golden Gate National Recreation Area to Sea-Level Rise
USGS Open-File Report 2005-1058

Map of Coastal Vulnerability

Skip past contents informationTable of Contents link to Title Page Link to Abstract Page Link to Introduction Page Link to Data Ranking Page Link to GGNRA Link to Methology Page Link to Geologic Variables Page Link to Physical Process Variables Page Link to Calculating the Vulnerability Index Page Link to Results Page Link to Discussion Page Link to Conclusions Page Link to References Page

Discussion

The data within the coastal vulnerability index (CVI) show variability at different spatial scales (Figure 11). However, the ranked values for the physical process variables vary less over the extent of the shoreline. The value of the relative sea-level rise variable is between low and moderate vulnerability. The significant wave height vulnerability is very low to high. The tidal range is mostly high vulnerability (1.0- 2.0 m) for all of GGNRA, with the exception of Bolinas Lagoon (very high vulnerability), and therefore contributes little to the variability of the CVI

The geologic variables show the most spatial variability and thus have the most influence on CVI variability (Figure 11). Geomorphology in the park includes very high vulnerability sandy beach shoreline, high vulnerability gravel beaches and engineered structures, moderate vulnerability alluvium and unconsolidated cliffs, and low and very low vulnerability rock and cliff features (Figure 3 A-E and Figure 4 A-G). Vulnerability assessment based on shoreline change is mostly moderate vulnerability with a few small areas of high vulnerability (Figure 6). Regional coastal slope is in the very low to very high vulnerability range for GGNRA.

The most influential variables in the CVI are geomorphology, coastal slope, and mean significant wave height; therefore they may be considered the dominant factors controlling how GGNRA will evolve as sea level rises.

Although there is parkland along Tomales Bay that lies within the legislative boundary of GGNRA, the area is managed by Point Reyes National Seashore. From a GGNRA management perspective there was a need to create another coastal vulnerability map that excludes the Tomales bay region from the rest of the vulnerability assessment. The map result of this analysis is shown in Figure 13. This map is considered supplemental for park managers and Figure 11 displays the results of the CVI analysis that this report is based upon.

Figure 3. Geomorphologic features within the northern section of GGNRA.
Figure 3. Geomorphologic features within the northern section of GGNRA. Click on figure for larger image.

Figure 4. Geomorphologic features within the southern section of GGNRA.
Figure 4. Geomorphologic features within the southern section of GGNRA. Click on figure for larger image.

Figure 6. Shoreline change rates for GGNRA.
Figure 6. Shoreline change rates for GGNRAA. Click on figure for larger image.

Figure 11. Relative Coastal Vulnerability for GGNRA.
Figure 11. Relative Coastal Vulnerability for GGNRA. Click on figure for larger image.

Figure 13. A supplemental CVI was calculated for GGNRA that excluded park lands along Tomales Bay that are managed by Point Reyes National Seashore.
Figure 13. A supplemental CVI was calculated for GGNRA that excluded park lands along Tomales Bay that are managed by Point Reyes National Seashore. Click on figure for larger image.

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