Potential Future Land Loss of Small Islands of Puerto Rico and the United States Virgin Islands FINAL REPORT for Project Number: R-111-1-10 to University of Puerto Rico Sea Grant College Program Mayagüez, Puerto Rico by David M. Bush William J. Neal Pablo Llerandi-Román Chester W. Jackson, Jr. August 5, 2013
INTRODUCTION Understanding how shorelines respond to rising sea level is critical for developing sound coastal management and land use planning guidelines, and is even more important when considering the effect on small islands. Commonly applied coastal recession models are less than adequate in predicting coastal evolution. Such models typically lack adequate baseline data or do not consider local complexities in sufficient detail. Add to this the uncertainty of change in rate of future sea-level rise, and most results are not much better than a simple slope/retreat model. In this study we evaluated potential shoreline change and associated land loss as a result of continuing sea-level rise of selected associated islands of Puerto Rico and the United States Virgin Islands (USVI). Three techniques of predicting change were employed: (1) the simple slope-retreat model, (2) extrapolation of historical shoreline change, and (3) a modification of the Coastal Vulnerability Index (CVI) currently in use in the United States and Canada, but applied here for the first time to small islands. The modification to the CVI required field and remote mapping of the islands to be able to better predict potential changes for each island subenvironment. State-of-the-art software was employed to assess shoreline change and perform CVI analyses for each location using AMBUR and a recently developed hazard-vulnerability assessment tool called AMBUR-HVA. Outreach was a second major task of the project. To that end, a field- and inquiry-based professional development workshop was held for in-service teachers, graduate students, and informal educators. The original plan was to hold two workshops, one in Puerto Rico and one in the U. S. Virgin Islands. However, owing to financial limitations, a single workshop was held, in Humacao, with attendees from the USVI. No perfect model exists to predict coastal recession during times of rising sea level. The most commonly used model has been the Bruun Rule (Bruun, 1962). That model and similar 1