PREDICTING SEDIMENT YIELD IN A TROPICAL WATERSHED: A GIS-BASED CONCEPTUAL MODEL

Jobos Bay is the second largest estuary on the island of Puerto Rico. It is a part of the National Oceanographic and Atmospheric Administration-National Estuarine Research Reserve (NERR) program. Various institutions over the years have studied this area extensively; specifically, studies monitoring water and sediment quality within the bay have been conducted. However, there is a dearth of knowledge on the influence of watershed characteristics and processes on sediment production, transport and delivery from the watershed to the bay. This information is a critical component in understanding sediment dynamics within the watershed as well as fate and transport of pollutants. In this study, a conceptual modeling framework was developed and implemented within a Geographic Information System (GIS). The framework conceptualizes hydrologic and geomorphic response in watersheds. In addition, areas of sediment potential and limitations were identified within the landscape. Results from this study indicated that cultivated areas had the highest potential for sediment delivery to the bay. All other areas exhibit moderate to moderately high source potential of transportable sediments. Sediment delivery to coastal ecosystems or the lack thereof is a major concern for the scientific community. Tropical coastal ecosystems surrounding islands are especially vulnerable due to the close coupling between the landscape and coast. The findings from this model provided insight into the importance of watershed geomorphology in generating and transporting sediment through and out of the landscape.