A NEW HURRICANE COASTAL IMPACT SCALE–CONTINUED WORK

The idea for a new Hurricane Impact Scale (HIS) emphasizing coastal impact at landfall evolved from several field studies and discussions with Orrin Pilkey. The well-known Saffir-Simpson Scale (SSS) is a good representation of hurricane strength over open water and of damage potential over land, but lacks an indicator of size of the storm. The proposed HIS uses three parameters to rank hurricanes: (1) maximum elevation of storm surge, (2) storm surge spread (coastal length impacted by higher water level), and (3) wind speed (SSS category). A ranking of 1-5 is given for each of the 3 criteria, making the possible range of HIS values 3-15. The HIS provides a broader range of categories than the Saffir-Simpson Scale (15 versus 5) and allows more precise classification for predictive (prestorm) and comparative (poststorm) modes.

Other investigators have suggested new hurricane scales. Balsillie (1999) uses the event longevity parameter (ELP—storm surge height and duration) as a measure of volumetric beach and coast erosion from hurricanes, but does not include length of shoreline impacted (size of the hurricane). A storm impact scale for barrier islands (Sallenger, 2000) compares water level versus barrier island elevation at landfall, but it also does not include a measure of length of shoreline impacted. The National Hurricane Center is working to include inland winds and rainfall potential as part of a revised hurricane scale, but those are inland effects.

The ultimate goal of the proposed HIS is a tool for hurricane/weather forecasters to give coastal residents more information for preparing for a storm’s potential impact. As an example, Hurricane Andrew (1992) was one of the strongest storms on record (SSS category 4) but it was also a relatively small storm. Opal (1995) was a weaker storm (category 3) but it was much larger. Although Andrew caused a tremendous amount of inland wind damage, Opal actually caused more shoreline erosion and overwash. The HIS rankings reflect this (Andrew-8, Opal-11). Inclusion of the SSS in the HIS reflects the critical nature of storm strength in any such scale. Two storm surge parameters are justified because storm surge is the best measure of a hurricane’s energy flux at the shoreline, and thus the potential for erosion, overwash, and property damage at and near the shore.