The Hydrogeomorphic Approach to Functional Assessment for Piedmont Slope Wetlands

Wetland functions are the characteristic activities (biological, chemical, and physical processes) that occur in these ecosystems. Functional assessment models are used to quantify the functional capacity of individual wetlands. The Hydrogeomorphic (HGM) Approach to functional assessment of wetlands classifies wetlands to the regional subclass level and then creates a model for an individual subclass in a given geographic area. An HGM model is essentially a functional profile that describes the physical, chemical, and biological characteristics of wetlands in the regional subclass, identifies those functions that are most likely to be performed on a sustained basis, and addresses landscape and ecosystem attributes that can be expected to influence each targeted function. The HGM Approach does not assign absolute values to functional capacity. Instead it rates functional capacity for a given wetland relative to reference standards-the highest level of functional capacity exhibited by wetlands in the regional subclass. Reference standards are established by assessment of wetlands that exhibit those attributes consistent with maximum sustained functional capacity. The HGM Approach is presently being applied to Piedmont slope wetlands in the Mid-Atlantic Region.