Types of Seasonal Streams
Almost 60% of streams in the US only flow seasonally or after storm events1. These are called intermittent streams and ephemeral streams, and are very important to the health of the downstream waters. They serve many of the same ecological roles as larger downstream sections. Wetlands are often associated with these stream systems.
Intermittent streams are those where groundwater provides stream flow for part of the year. Runoff from rainfall supplements the stream flow, but intermittent streams may dry up part of the year.
In ephemeral streams, surface runoff from precipitation is the primary source of stream flow. Flowing water may occur only during rain events, and may be short in duration. These streambeds are above the water table throughout the year and receive no groundwater flow.
Headwaters (also called headwater streams) are the upper reaches of a non-tidal stream where the average annual flow of the stream is less than 5 cubic feet per second. According to the EPA, 53% of total stream miles in the continental US are headwaters.
Seasonal Stream Jurisdiction Under the Clean Water Act
Not all intermittent, ephemeral, and headwaters are regulated by the US Army Corps of Engineers (USACE). However, it can be difficult to determine if this is the case for each stream. Any wetlands associated with these systems may or may not be jurisdictional. These streams may be jurisdictional if they are flowing directly or even indirectly into what USACE determines to be a traditionally navigable waterway. These jurisdictional determinations are made on a case-by-case basis by the USACE.
| Jurisdictional Determination Definition A written USACE determination that a wetland and/or waterbody is subject to regulatory jurisdiction under Section 404 of the Clean Water Act (33 U.S.C. 1344) or a written determination that a waterbody is subject to regulatory jurisdiction under Section 9 or 10 of the Rivers and Harbors Act of 1899 (33 U.S.C. 401 et seq.). |
Click here to read more about the the USACE regulatory permit process and find contact information on how to request a jurisdictional verification.
