Baseline for the islands of Vieques and Culebra, Puerto Rico, generated to calculate shoreline change rates using the Digital Shoreline Analysis System version 5.1

The U.S. Geological Survey (USGS) maintains shoreline positions for the United States coasts from both older sources, such as aerial photographs or topographic surveys, and contemporary sources, such as lidar-point clouds and digital elevation models. These shorelines are compiled and analyzed in the USGS Digital Shoreline Analysis System (DSAS), version 5.1 software to calculate rates of change. Keeping a record of historical shoreline positions is an effective method to monitor change over time, enabling scientists to identify areas most susceptible to erosion or accretion. These data can help coastal managers understand which areas of the coast are vulnerable to change. This data release, and other associated products, represent an expansion of the USGS national-scale shoreline database to include Puerto Rico and its islands, Vieques and Culebra. The USGS, in cooperation with the Coastal Research and Planning Institute of Puerto Rico—part of the Graduate School of Planning at the University of Puerto Rico, Rio Piedras Campus—has derived and compiled a database of historical shoreline positions using a variety of methods. These historical shoreline data are then used to measure the rate of shoreline change over time. Rate calculations are computed within a geographic information system (GIS) using the DSAS version 5.1 software. Starting from a user defined baseline, measurement transects are created by DSAS that intersect the shoreline vectors. The resulting intersections provide the location and time information necessary to calculate rates of shoreline change. The overall project contains shorelines, baselines, shoreline change rates (long-term and short-term), and shoreline intersects (long-term and short-term), for Puerto Rico, and the adjacent islands of Vieques and Culebra.