Waters of the United States includes essentially all surface waters such as all navigable waters and their tributaries, all interstate waters and their tributaries, all wetlands adjacent to these waters, and all impoundments of these waters.
WETLANDS
“Wetlands” are areas characterized by growth of wetland vegetation (bulrush, cattails, rushes, sedges, willows, pickleweed) where the soil is saturated during a portion of the growing season or the surface is flooded during some part of most years. Wetlands generally include swamps, marshes, bogs, and similar areas.
The U.S. Army Corps of Engineers provides a brochure on the importance of Recognizing Wetlands as well as The Value to the Nation of our wetlands.
ORDINARY HIGH WATER MARK (OHWM)
The landward regulatory limit for non-tidal waters (in the absence of adjacent wetlands) is the ordinary high water mark. The ordinary high water mark is the line on the shores 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 the soil
Destruction of terrestrial vegetation
Presence of litter and debris
Other appropriate means that consider the characteristics of the surrounding areas
NAVIGABLE WATERS
Navigable waters of the United States are defined as tidal waters and waters that have been used in the past, are now used, or are susceptible to be used as a means to transport interstate or foreign commerce up to the head of navigation. Section 10 and/or Section 404 permits are required for construction activities on these waters.