Over the next few years it is anticipated that Guam will experience significant growth due to military relocations and increasing tourism, which comes at a price to environmental resources. Because of the anticipated rapid growth, pressure will be placed on regulatory agencies to review projects without carefully considering the cumulative and secondary impact (CSI) effects they may have on the environment. CSIs due to developments are “impacts that may be insignificant by themselves but when combined with other development impacts in an area over time become a significant problem” (National Oceanic and Atmospheric Administration [NOAA], 2012). A policy is needed to protect the environment from CSIs due to developments; however, tools are needed to assist in the formation of this policy.

The objective of this study is to use Geographic Information System (GIS) technology to create a tool to screen for potential CSIs. This objective was met by achieving the goals of this study, which are to (1) develop the Northern Guam Geodatabase, (2) create an Affected Areas Tool, and (3) quantify effects from different development scenarios for Northern Guam.

The Northern Guam Geodatabase developed in this project contains 29 feature datasets and 5 raster datasets portraying geographic information about Northern Guam. The Affect Areas Tool is a GIS-based tool that utilizes inputs from the Northern Guam Geodatabase to screen the resources that may be affected by future developments. For determination of CSIs, a benefit of GIS datasets is that they can be used to inventory, evaluate, and predict future environmental changes. The outcome of the land development scenarios considered here indicates that for Northern Guam, undeveloped lands will be converted to urban/built-up areas with forested areas being affected the most. Furthermore, the potential uses of this tool to manage water and environmental resources of Northern Guam are discussed.