SHELF WIDTH, SHORELINE CURVATURE, AND HURRICANES: CONTINUED DEVELOPMENT OF A NEW HURRICANE IMPACT SCALE

A new Hurricane Impact Scale (HIS) has recently been proposed which will better reflect the potential for erosion and overwash at the coast (Jackson et al., 1999; Bush et al., 2000). The Saffir-Simpson Scale (SSS) is the current method used for comparing hurricane strength and predicting potential damage. The SSS is a suitable reflection of hurricane strength over the open ocean, however, the scale is less adequate in reflecting the effects of a hurricane on the coast at landfall because it does not take storm surge and other land-sea interactions into account. The 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 (as the storm is approaching based on potential landfall sites) and comparative modes (a single HIS ranking based on post-storm measurements). Storm surge is a good measure of a hurricane's energy flux at the shoreline, and thus the potential for erosion, overwash, and property damage. As part of the continued refinement of the HIS, the effects of shelf width and shoreline curvature on storm surge are being investigated and quantified. The relationships between shelf width, shoreline curvature and storm surge are qualitatively straightforward: the wider the shelf and the more deeply embayed the shoreline, the greater the potential storm surge. Shoreline curvature can be considered at several spatial scales, from regional to local. A "Width/Curvature Index" is presented to quantitatively rate shoreline segments along the USA southeastern Atlantic and Gulf of Mexico coasts.