The hydrogeomorphic (HGM) classification for wetlands was developed as a starting point for applying functional assessments used in the determination of the effects of impacts (Brinson 1993a). The main purpose of the classification was to aggregate wetlands with similar geomorphic settings so that altered or degraded conditions could be evaluated relative to unaltered states. In so doing, wetland assessments could be tailored to a much narrower range of natural variation than if a single assessment procedure was designed for all wetland classes. By controlling for the degree of natural variation through classification, alteration due to human activities could be detected more effectively (Smith et al. 1995). Although

Soil Taxonomy

(Soil Survey Staff 1975) was not taken into account in this classification, we recognize that many of the same factors associated with geomorphic setting are also related to soil. Geomorphic setting of wetlands is used in this chapter to examine the correspondence between wetland characteristics and soils.