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A habitat degradation index (HDI) was developed by the NAWQA Program to indicate habitat conditions at a site (Gilliom and others, 1998). An HDI score for a site was calculated by summing the ranks of three parameters; the amount of stream modification, bank erosion, and bank vegetative stability. Site scores were then grouped into three degradation classes; significantly degraded, moderately degraded, and minimally degraded. Gilliom, Robert J., Mueller, David K., and Nowell, Lisa H., 1998, Methods for comparing water-quality conditions among National Water-Quality Assessment Study Units, 1992-1995: U.S. Geological Survey Open-File Report 97-589, 54 p. |