APPLICATION OF THE STORM EROSION INDEX (SEI) TO THREE UNIQUE STORMS

Abstract

During 2012 and 2013, the State of Florida was impacted by three tropical weather systems (Debby, Isaac, and Sandy) that caused significantly more beach erosion than similar, traditionally classified storms. Here, the storms are reclassified using the more recently developed Storm Erosion Index (SEI) which takes into consideration both the storm tide and storm waves, as well as the storm duration. The SEI has been shown previously to accurately represent the impact of coastal storms at a number of other sites (Miller and Livermont, 2008). When reanalyzed with the SEI, Tropical Storm Debby was found to be more significant in terms of beach erosion potential than any other storm in the record (since 1996), ranking as a "Category 5" storm with a return period of 23.4 years. Hurricane Isaac, which followed closely on the heels of Debby, ranked as a "Category 2" storm with an associated return period of 3 years. A sensitivity analysis performed on the results indicated that the wave steepness threshold used to separate erosion and accretion was particularly important during Isaac, as the conditions throughout the storm remained close to the threshold. While Hurricane Sandy is more known for the devastation it caused in the northeast, it also caused significant beach erosion in the State of Florida. The SE I more accurately reflects the significance of the beach erosion experienced during Sandy, and ranks the storm ahead of all of the other storms in the record (since 1994), including Hurricanes Frances, Gordon, and Jeanne which all made landfall near the area considered. Overall, Sandy registered as a "Category 5" storm in terms of beach erosion potential, with a return period of 40.5 years.