INVESTIGATING THE USEFULLNESS OF THE USGS COASTAL VULNERABILITY INDEX: REALIZED AND POTENTIAL IMPACTS OF STORM SURGE EVENTS ON THREE DIFFERENT ATLANTIC AND CARIBBEAN COASTLINES: DELMARVA PENINSULA, VIRGINIA; FLORIDA KEYS, FLORIDA; AND CURACAO, NETHERLANDS ANTILLES

Coastal landscapes are among the most familiar landscapes observed by the average American college student. Yet for as much time as we spend recreating in these landscapes, we fail to appreciate the geologic and biologic processes that shape them. We understand little about how these dynamic features change in response to storm events and sea-level change, much less how they can be effective in protecting our growing coastal communities and natural resources if they themselves are protected. Coastal ecosystems, when functioning properly, have natural lines of defense that function to protect coastlines by dampening the effects of storm surge and limiting the amount of flooding and erosion.

The U.S. Geological Survey implements a Coastal Vulnerability Index (CVI) for assessing the sensitivity of a coastline to sea-level rise. This CVI uses six physical variables (geomorphology, annual shoreline erosion rates, slope, rate of sea-level rise per year, mean tidal range, and mean wave height) to assign a risk value for each variable based on the “potential magnitude of its contribution to physical changes” of the coast as sea-level rises (Thieler & Klose, 1999). The geomorphology variable “expresses the relative erodibility of different landform types” (Thieler & Klose, 1999); those types assigned a risk value of 5, or “very high”, include barrier beaches, salt marshes, mangroves, and coral reefs. However, these coastal ecosystems, when functioning properly, have proven to be invaluable for their ability to minimize damage to coastlines from storm surge. The risk values assigned by the CVI need to be re-examined in order to compensate for the mitigation abilities of those landform types included in the highest-risk category.

This study investigates three different coastal ecosystems (Virginia salt marsh – barrier island complexes, Florida reef – mangrove complexes, and Curacao reef – terrace complexes) and their underlying geomorphology and ecology in order to understand how they function to minimize the impact of storms. Each case study is based on coastal changes attributed to specific storm events through pre- and post-storm assessments.