Comment:

To compute a Natural Habitat exposure rank for a given shoreline point, the model determines whether a certain class of natural habitat (Example Ranking Table) is within a user-defined search radius from the point. Equation explained in User's Guide. The model requires separate polygon shapefiles representing each natural habitat type, the rank, or level of protection offered by the habitat, and a protection distance, beyond which the habitat does not protect the coastline. The ranking proposed in Example Ranking Table (see Appendix B of User's Guide) is based on the fact that fixed and stiff habitats that penetrate the water column (e.g., coral reefs, mangroves) and sand dunes are the most effective in protecting coastal communities. Flexible and seasonal habitats, such as seagrass, reduce flows when they can withstand their force, and encourage accretion of sediments. Therefore, these habitats receive a lower ranking than fixed habitats. It is left to the user’s discretion to separate sand dunes into high and low categories. It is suggested, however, that since category 4 hurricanes can create a 5m surge height, 5m is an appropriate cut-off value to separate high (>5m) and low (<5m) dunes. If the user has local knowledge about which habitats and dune elevations provide better protection in their area of interest, they should adjust the values in Example Ranking Table accordingly.