A Hydrogeomorphic Approach ((HGM) )is a functional assessment method which compares a wetland's condition to similar wetland types (as defined by HGM classification) that are relatively unaltered.

HGM functions normally fall into one of three major categories:
1) hydrologic (e.g., storage of surface water),
2) biogeochemical (e.g., removal of elements and compounds), and
3) habitat (e.g., maintenance of plant and animal communities).

List of books: Hydrogeomorphic,Approach