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Video by Sgt. David Marquis

A-Roll: Tracie Nadeau, Environment Protection Agency Research Scientist

U.S. Army Corps of Engineers, Engineer Research and Development Center

Oct. 26, 2022 | 7:33

Researchers from the Engineer Research and Development Center's Cold Regions Research and Engineering Laboratory, the Environmental Protection Agency, and regulators from the U.S. Army Corps of Engineers test a data worksheet from the National Ordinary High Watermark Manual which the group has been developing for ten years. During the field test, the group traveled to several types of bodies of water throughout Vermont, using the OHWM datasheet to identify the highest watermark for each type of water system. The ordinary high water mark (OHWM) defines the lateral extent of non-tidal aquatic features in the absence of adjacent wetlands in the United States. The federal regulatory definition of the OHWM, 33 CFR 328.3(c)(7), states the OHWM is “that line on the shore established by the fluctuations of water and indicated by physical characteristics such as [a] clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas.” This is the first manual to present a methodology for nationwide identification and delineation of the OHWM. A two-page data sheet and field procedure outline a weight-of-evidence methodology to organize and evaluate observations at stream sites. This manual presents a consistent, science-based method for delineating the OHWM in streams. It also describes regional differences and challenges in identifying the OHWM at sites disturbed by human-induced or natural changes and illustrates how to use remote data to structure field inquiries and interpret field evidence using the principles of fluvial science. The manual demonstrates that, in many landscape settings, the OHWM may be located near the bankfull elevation.