The ordinary high water mark (OHWM) defines the lateral extent of nontidal 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.”
The National OHWM Field Delineation Manual for rivers and streams: Final Version can be accessed and downloaded through the engineer Research & Development Center (ERDC) website by clicking here. 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 (WoE) 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.
OHWM Regional Supplements
Nationwide:
Arid West:
Western Mountains, Valleys and Coast supplements:
Rapid Ordinary High Water Mark (OHWM) Identification Data Sheet (September 2024)
Assessing Stream Duration
Regional Stream flow Duration Assessment Methods (SDAMs) -
The U.S. Army Corps of Engineers (Corps) Albuquerque, Chicago, Detroit, Fort Worth, Galveston, Kansas City, Los Angeles, Omaha, Rock Island, Sacramento, San Francisco, St. Louis, St. Paul, and Tulsa Districts, and the U.S. Environmental Protection Agency (EPA), Regions 5, 6, 7, 8, and 9 jointly announce the availability of the Regional Streamflow Duration Assessment Methods (Regional SDAMs) for the Arid West, Western Mountains and Great Plains. The methods are rapid assessment tools for distinguishing between ephemeral, intermittent, and perennial streamflow at the reach scale for the Arid West, Western Mountains and Great Plains regions. For background information, SDAM development, instructions/training materials for completed SDAMs, and field form information please visit EPA's SDAM webpage .
NOTE - SDAMs are region specific, please download and view the map of SDAM regions
Regional SDAM manuals and data forms: