A New Focus on Wetland Functions

By: Emily Drahos

I have always enjoyed the outdoors. Playing in the creek behind my childhood home, building zip lines in the woods with my brother, riding horses, hiking with my grandparents, camping with my father, and gardening with my mother and grandmother are some of my fondest childhood memories. While I still enjoy these activities, I now have a greater appreciation for nature. After studying and practicing wetland science, I realize that nature is not only beautiful; it is also beneficial. Wetlands provide many ecosystem services that benefit all living things – water filtration, flood protection, nutrient cycling, groundwater recharge, and wildlife habitat are just a few. Worldwide, wetland ecosystem services are valued at over 14.9 trillion dollars (EPA, 2016).

Due to their importance to humans and the environment, wetlands are protected through several regulatory mechanisms. In the United States, the main mechanism of federal wetland regulation is through Section 404 of the Clean Water Act of 1972 (CWA). Section 404 directs the United States Army Corps of Engineers (USACE) to administer a regulatory program for permitting the discharge of dredged or fill material into waters of the United States, including wetlands. As a part of the permit review process, wetland functions must be assessed (Smith, 1995). The wetland functional assessment is then used to evaluate wetland impacts associated with different alternatives and to develop proposed mitigation. Wetland mitigation must adequately replace the lost wetland acreage and functions, as described in the “No Net Loss” mitigation policy of 1989.

In 1993, the White House Office on Environmental Policy indicated a standardized approach for assessing wetland functions. The selected approach, the hydrogeomorphic (HGM) wetland assessment, emphasizes geomorphology and hydrology, unlike other assessment models that focus on biotic components or subjective human values (Clairain, 2002). In 1997, USACE, the United States Department of Transportation (USDOT), the United States Department of Agriculture’s (USDA’s) Natural Resources Conservation Service (NRCS), the United States Fish and Wildlife Service (USFWS), and the United States Environmental Protection Agency (USEPA) decided to use HGM as the basis of their functional assessments (NRCS, 2008). Federal agencies also agreed to develop regional HGM guidebooks that would provide detailed ways of determining wetland functions within a physiographic region (USACE et al., 1997). As of today, two national and twenty-nine regional HGM guidebooks have been published.

My career, as well as the Virginia Tech Executive Master of Natural Resources (XMNR) program, has allowed me to further explore my interest in wetland science, HGM functional assessments, and HGM guidebooks. My experience modifying HGM regional guidebooks to fit the physiographic region, project schedule, and project constraints of Route 460 Project Southeast Virginia further catalyzed my interest in wetland functional assessments and spurred my desire to join the XMNR program as a graduate student while continuing to work full-time. During the XMNR coursework, I was able to continue exploring HGM functional assessments through the program’s Individual Development Process. My independent directed study, Strengths and Shortcomings of Current Hydrogeomorphic (HGM) Assessment Models – Analysis and Recommendations for Riverine HGM Guidebooks Applicable to Virginia Wetlands, looks at the history of HGM assessments, analyzes published HGM guidebooks applicable to Virginia riverine wetlands, and provides suggestions to improve usability for today’s users.

Modifying and writing new HGM guidebooks to better serve today’s users is a time-consuming and expensive task. I hope that this study prompts environmental professionals to assess the current status of HGM functional assessments and evaluate ways to make guidebooks more useful for today’s purposes.


  • Clairain, E. J. Jr. 2002. Hydrogeomorphic Approach to Assessing Wetland Functions: Guidelines for Developing Regional Guidebooks. Chapter 1, Introduction and Overview of the Hydrogeomorphic Approach. ERCD/ELTR-02-3, US Army Engineer Research and Development Center. Vicksburg, Mississippi.
  • Natural Resources Conservation Service (NRCS). 2008. Hydrogeomorphic Wetland Classification System: An Overview and Modification to Better Meet the Needs of the Natural Resources Conservation Service.
  • Smith, R.D., Ammann, A., Bartoldus, C., and Brinson, M.M. 1995. An Approach for Assessing Wetland Functions Using Hydrogeomorphic Classification, Reference Wetlands, and Functional Indices. Technical Report WRP-DE-9. U.S. Army Engineer Waterways Experiment Station. Vicksburg, Mississippi.
  • United States Army Corps of Engineers (USACE) et. al. 1997. The National Action Plan to Implement the Hydrogeomorphic Approach to Assessing Wetland Functions. Federal Register: June 20, 1997, Volume 62, Number 119.
  • United States Environmental Protection Agency (USEPA). 2016. Economic Benefits of Wetlands. Retrieved from https://www.epa.gov/sites/production/files/2016-02/documents/economic benefits.pdf.


Emily Drahos is an alumna of Virginia Tech’s Executive Master of Natural Resources program (2017), and received her BS in Environmental Science from the University of Virginia (2013). She has over five years of professional experience in the environmental industry, and is currently working as an environmental scientist at Whitman, Requardt, and Associates, LLP in Richmond, Virginia. Emily performs a variety of natural resources services for public sector clients, and maintains certification as a Virginia Professional Wetland Delineator and an erosion and sediment control inspector.

The Center for Leadership in Global Sustainability thanks *saipal; Henry; and Emily Drahos for making their photographs available for use through a Creatives Commons license.