Shoreline changes in Puerto Rico (1936-1993)

study of historic shoreline changes was conducted at 29 selected sites in Puerto Rico from 1936 to 1993, to document changes in shoreline position and describe qualitatively and quantitatively the possible causes that could produce these changes. Shoreline changes were measured by overlays developed from aerial photos. Descriptions of physical and geomorphological variables were done to identify the possible causes of shoreline changes. These were studied using remote sensing techniques, published reports, maps and field observations. Monthly beach profiles were measured at nine of the 29 sites from 1992 to 1993. These data were organized in a databank for ease in understanding the data and to perform statistical tests (Krustal-Wallis and Spearman Rank Correlation).;Most of the beaches included in the profiling study were transitional from 1992 to 1993. Reflective and dissipative stages were measured on some occasions on these beaches. Carbonate and mixed nearshore sands were discriminated based on radiance values and the similarities found between the images and sediment maps. Discrimination of bottom marine facies is difficult to conduct with TM due to the small ranges of radiances found in the Puerto Rican nearshore waters.;Based on the results, many factors caused shoreline changes on beaches around Puerto Rico from 1964 to 1987. These were: (1) human activities, (2) lack of sand deposits in the nearshore area, (3) variability in the wave regime, (4) flood events of all magnitudes and frequencies, (5) the presence of submarine canyons, and (6) increase in tropical storm occurrence in the vicinity of the island. None of the variables were significant in causing shoreline changes based on the statistical significance at...