Seasonal shoreline changes along the north coast of Puerto Rico, from Isla de Cabras to Aguadilla

Abstract

Seven beaches were studied along the north coast of Puerto Rico in order to qualitatively compare seasonal changes for each system. These are Punta Borinquen, Aguadilla, Jobos, Isabela, Camuy, Arecibo port, Mameyal, Vega Baja, Palmas Atlas, Barceloneta, and Isla de Cabras, Cataño. Field data was collected during two sampling periods: March (dry season) and September (wet season) of 2003. Satellite images processing, beach profiling, sediment composition and sediment texture (grain size) were studied in each site. The beach systems studied were classified as reflective or dissipative systems according to topographical survey data. As for sand movement, it is noticeable in the beach profiles that there is movement to the west side of each system. There does not seem to be a significant change in sediment texture and composition between seasons, probably influenced by the presence of major river systems discharging near most systems and to the dynamic conditions in the north coast all year round. Landsat-7 satellite images were used in a prior study to discriminate bottom sediment types in the nearshore areas. Higher spatial resolution was recommended (Barreto et al, 1998). In this study, IKONOS images were chosen because of better spatial resolution (1 meter). After several pre-processing methods and due to missing image acquisition information, no valid classifications were made. It became evident that not only is spatial resolution important, but spectral resolution is important as well. A better assessment might have been possible if reflectance values would have been calculated, but due to the fact that the exact date and time of image acquisition were not available this could not be accomplished. Radiance values were used instead but the varying range among these did not prove useful.