The Hydrogeomorphic Method (HGM) of wetland classification classifies wetlands by their landscape position and hydrology. Hydrologic types used in HGM are Riverine, Depressional, Mineral Soil Flats, Organic Soil Flats, Slope, Lacustrine Fringe, and Estuarine Fringe.
Primary HGM work done in Oregon to date are assessments completed by Paul Adamus for the Oregon Department of State Lands. This work was done for the Willamette Valley (2001) and coastal salt marshes (2006).