Hydrogeomorphic (HGM) Approach to Assessing Wetland Functions: Guidelines for Developing Guidebooks (Version 2)

Abstract

The Hydrogeomorphic (HGM) Approach for assessing wetlands was developed by the U.S. Army Corps of Engineers as a procedure for assessing the capacity of a wetland to perform ecological functions. The Approach requires classification of wetlands based on geomorphic setting, water source, and hydrodynamics. The objective of the Guidelines for Guidebook Development is to provide detailed guidance on methods and procedures that have proven helpful in developing existing guidebooks. This document contains an overview of the HGM Approach; how to classify and characterize wetland subclasses; developing assessment models; selecting reference wetlands and managing reference wetland data; testing and calibrating models; developing assessment protocols for using assessments; validating assessment models; and assessment application examples.

Operational draft regional guidebook for the rapid assessment of wetlands in the North Slope Region of Alaska

“…This section provides the definition, rationale, characteristics, and assessment equations utilized to quantify wetland functions (e.g., habitat, hydrology, and biogeochemical cycling) and the on-site assessment modifier when on-site data are available. Although the rapid assessment approach does not directly measure wetland functions, surrogate measures related to function have been utilized in a variety of methodologies (Smith et al, 1995;2013). These surrogate measures have been successfully related to wetland functions in several studies .…”

“…Additionally, a description of the wetland classes occurring within the region is provided. The development of the assessment guidebook followed the guidance provided by Smith et al (2013) for wetland assessments including: (1) ecosystem classification, (2) assessment variable and equation calibration based upon reference data, (3) a written protocol for data collection, (4) peer review, and (5) verification of results. This guidebook was developed and underwent peer review with the input of a multi-agency, interdisciplinary development team including wetland scientists from USACE, USEPA, USFWS, USDA-NRCS, academia, and experts from the private sector.…”

HGM: a call for model validation

“…Smith et al (2013) note that validation is a part of the development of HGM models, though it is deemed ''optional'' (p. 13). Few models seem to reach this level of review as Smith et al (2013) note: ''…validation is a more complex and time-consuming aspect of testing and calibration that can involve years of additional research and data gathering that is far beyond the interests, capabilities, or responsibilities of the assessment team and generally not part of typical guidebook development.'' While this might have been a reasonable statement to make in 1993, it seems substantially less so twenty years into the process.…”

“…The first thing to do to address the issues is to begin to follow the advice in the first part of Smith et al (2013) concerning ''…additional research and data gathering…'' I will grant that this is not a trivial task but it is a necessary one. Given that most models are now regionalized, this effort has to occur across the country in a number of locations.…”

“…The development of HGM models is described in detail in Smith et al (2013). To summarize that process, the first step is the collection of experts with experience in a particular region.…”