The term "waters of the United States" has been broadly defined by statute, regulation, and judicial interpretation to include all waters that were, are, or could be used in interstate commerce such as interstate lakes and rivers as well as intrastate lakes, rivers, streams (including ephemeral streams), mudflats, wetlands, sloughs, prairie potholes, playa lakes, and ponds.
"Wetlands" are areas characterized by growth of wetland vegetation (bulrush, cattails, rushes, sedges, willows, pickleweed, andiodine bush) 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 landward regulatory limit for 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 erosion line impressed on the bank;
- changes in the character of the soil;
- destruction of terrestial vegetation due to inundation;
- the presence of litter and debris;
- stain marks on rocks or bridge piers;
- orother appropriate means that consider flow characteristics of the stream.