GEOLOGIC AND GEOMORPHIC CONTROLS ON DAMAGE IN PUERTO RICO FROM HURRICANE GEORGES (1998)

Hurricane Georges made landfall on the eastern coast of Puerto Rico on September 21, 1998.Georges caused a storm surge of up to 3-meters, plus storm waves as high as 6 meters, causing $1.9 billion in damage along with severe coastal erosion. This study analyzes the pre-storm geomorphic setting to ascertain which parameters control damage. Previous studies of geomorphic controls on storm damage in Florida and South Carolina indicate that along those coasts, site elevation provided the best protection against property damage, followed by dune height (in front of the site) and beach width. A more recent study along the Mississippi coast after Hurricane Katrina indicates that catastrophic storms can over take all geomorphic controls in low lying areas, such as those struck by Hurricane Katrina. Puerto Rico’s geologic setting differs from the Florida and South Carolina study areas, which are barrier islands, and the Mississippi study area, which is a mainland coast behind small Gulf barriers. Puerto Rico’s coastline consists of mainly rocky cliffs, headlands, mangrove coasts, sand and gravel beaches, and in between many different artificial and hard stabilization structures. Geomorphic parameters assessed in this study include storm surge inundation line, geologic rock types, coastal morphology, FEMA Q3 flood zones, slope and digital elevation models. A regression analysis was used to determine which pre-storm coastal attributes influenced the observed post-storm storm-surge penetration and damage. Having a quantitative understanding of coastal hazard risk is critical for producing accurate risk maps, as well as, for prioritizing spending on mitigation.