Quantification of Landscape Indicators/Aquatic Resource Associations in the Savannah River Basin
The selected landscape indicators are identical to, or based on, indicators used in the mid-Atlantic atlas (Jones et al, 1997). In the atlas, the indicators were calculated only for 8-digit HUCs; in this study, indicators are additionally calculated for smaller spatial units. The basic methodology is the same, however. In general, calculation of the landscape indicators involves ARC/INFO techniques of extracting or "cookie cutting" the desired area from a spatial data set. The data are formatted in an ARC/INFO grid of uniform cell size. In this study, a 30-m cell size is used for all grids. For indicators which are produced from more than one data set (e.g., roads crossing streams), ARC/INFO overlay and intersection techniques are used. A few indicators, used only on the drainage areas of the individual sampling sites, are produced from an in-house custom statistics program. These are indicators of fragmentation, i.e., the degree to which landcover types are present in patches rather than in continuous, homogenous blocks. The landscape change indicator is produced from comparison of satellite imagery from two dates. This is the only indicator which does not use ARC/INFO as the primary data analysis software. Landscape change assessment employs ENVI, an image processing software package available for PC or Unix systems.