Sediment loss and its cause in Puerto Rico watersheds

Abstract. A major environmental concern in the Commonwealth of Puerto Rico is increased sediment load to water reservoirs, to estuaries, and finally to coral reef areas outside the estuaries. Sediment deposition has significantly reduced the storage capacity of reservoirs, and sediments, with their associated contaminants and nutrients that are adsorbed, can stress corals and negatively impact reef health. To prevent and manage sediment loss it is therefore important to understand local soil erosion and sediment transport processes. The main objective of this study was to determine the influence of landscape characteristics on sediment loss. We analyzed available precipitation and sediment data collected in Puerto Rico during the past three decades, as well as information on land use, soil properties, and topography. Our partial least squares analysis was not very successful in identifying major factors associated with sediment loss due to the complexity of the study's watersheds; however, it was found that topography and rainfall factors do not play a leading role. Sediment loss from the ridge watersheds in Puerto Rico was mainly caused by interactions of development, heavy rainfall events (especially hurricanes), and steep mountainous slopes associated with the ridges. These results improve our understanding of sediment loss resulting from changes in land use/cover within a Puerto Rico watershed, and allow stakeholders to make more informed decisions about land use planning.