This atlas, developed by WRI and NOAA, provides a series of spatial indicators of watershed-based sources of threat to coral reefs in the US Virgin Islands.

Executive Summary

Alteration of the natural landscape for development, road construction, or agriculture can have adverse impacts on coral reefs through increased delivery of sediment and pollution to coastal waters. The threat associated with land clearing is higher in areas of steep relief, intense precipitation, and where soils are erosive in nature.

This study uses several spatial and statistical techniques to characterize watersheds across the USVI with regard to relative erosion rates and the threat of land-based sources of sediment and pollutant delivery to coastal waters. A simplified version of the Revised Universal Soil Loss Equation (RUSLE) using slope, land-cover, precipitation, and soil characteristics is applied, as well as indicators of road density and erosivity by watershed.

Watersheds are an essential unit for analysis, since they link land areas with their point of discharge to the sea. The atlas presents a comparison of estimated watershed-based threat to coral reefs from both land cover change and road development.

Data assembled or developed under this collaboration, including analysis results, are published on the Coastal Data CD for the U.S. Caribbean, which is available by sending an e-mail to The data CD serves as a GIS data sampler for both the USVI and Puerto Rico, allowing users to do their own analysis of land-based sources of threat.

The atlas, Land-based Sources of Threat to Coral Reefs in the US Virgin Islands, provides a summary of some of the spatial indicators developed under the project. The atlas is available as both Full Report: High Resolution (for printing) and Full Report: Low Resolution (for screen display).

The project was implemented by the World Resources Institute (WRI) and the U.S. National Oceanic and Atmospheric Administration (NOAA), in collaboration with many local institutions and other partners. Collaborating institutions were vital sources of information, provided guidance on the analytical approach, and offered critical review of analysis results. Groups which contributed data or provided guidance on the project include: