Hydrogeomorphic classification and functional assessment

Wetland assessment methods have been used to estimate the capacity of wetlands to perform certain functions and to determine potential changes in wetland condition as a result of anthropogenic impacts. In this chapter, we describe the Hydrogeomorphic (HGM) Approach, a wetland functional assessment method that was developed to alleviate some of the shortcomings of other wetland assessment methods. The HGM approach is a reference-based assessment method that was developed to estimate change in wetland condition by quantitatively comparing ecosystem functions of altered wetlands to unaltered wetlands. The HGM approach involves a developmental phase and an application phase, but the focus of this chapter is on the application phase. Specifically, we describe how to conduct a wetland functional assessment using the HGM approach. The components of the HGM approach that are described include classifying wetlands using HGM classification, collecting data representing individual variables in functional models, calculating the functional capacity of the wetland, and analyzing the functional capacity results to determine potential impacts on wetland functions from proposed projects.