Whether or not an ephemeral stream needs an SMZ or not should be a site-specific determination made by a forester or other qualified professional. Factors which may warrant a necessity for an SMZ on an ephemeral stream might include: soil type, slope of surrounding land, vegetative cover, and volumes of expected flows. Some benefits of leaving an SMZ along an ephemeral stream include but are not limited to:
Ephemeral streams usually flow less than 30% of the year or just after rain events. If the flow of the stream can’t be determined, the presence of 3 or more of the following characteristics may help identify the stream as an ephemeral stream:
⦁ Site may have no well-defined channel.
⦁ Water pools are absent.
⦁ A flow area that is almost always straight and either “flattens” out at the bottom of the slope or grades into intermittent or perennial streams.
⦁ Fluctuating high water marks (flood prone width) and/or sediment transport are usually absent.
⦁ There is evidence of leaf litter and/or small debris jams in the flow area.
⦁ Wetland (hydrophytic) vegetation present is usually sparse or absent.
⦁ The side slope soil characteristics are typical of the surrounding landscape. Soil texture usually more loamy than the surrounding upslope landscape and usually has a clay subsurface.
⦁ Ephemeral streams are not typically identified on USGS topographic maps by solid or dot dash blue lines.