Special characterization of sandy beaches in western portion of Puerto Rico

Abstract

Remote sensing applications to beach system in Puerto Rico have been limited by low spatial resolution of the available images and lack of appropriate equipment for field validation. A GER-1500 spectroradiometer with a spectral range from 350 to 1050 nanometers was used to collect reflectance measurements in 15 sandy beaches in western Puerto Rico. Samples of the beaches were analyzed in the laboratory to determine the composition using sieving, XRD and grain counting to characterize the different components of the sand sediments. Results indicate a change in magnitude in the reflectance curve compared with the composition. Higher magnitude correlated with more carbonate material concentration in the sand and lower magnitude correlated with higher concentration of dark mineral. The reflectance shows a change in the slope of the reflectance curve between 450 to 550 nanometers that is present in all 15 beaches. The spectral slope in that range was calculated and related to the composition. The results of the field reflectance measurements were compared to high resolution (1m) IKONOS satellite images. Using band math these images showed a correlation with the field measurements. A methodology to obtain information about composition in sand beaches using remote sensing was developed using the slope of the reflectance curve. For the first time a spectral library of beach sand sediment for western Puerto Rico was created.