Intermittent Streams

BMP guidelines recommend that a minimum of a 50 foot SMZ be left on both sides of a intermittent stream in order to filter sediment from overland flow and to provide shade for stable water temperature.  Other benefits of leaving an SMZ include but are not limited to: providing travel corridors and habitat for wildlife, adding aesthetic quality to a harvest area, and possibly reducing your property taxes.

Intermittent streams flow at least 30% to 90% of the year under normal conditions.  If the flow of the stream can’t be determined, the presence of 5 or more of the following characteristics may help identify the stream as an intermittent stream.

The stream shows evidence of a well-defined channel.

Water pools are absent during dry conditions but are present during wet conditions.

Fluctuating high water marks (flood prone width) and/or sediment transport are evident. Indications of a flood prone zone parallel to a stream course are sediment deposits, sediment stained leaves, bare ground and/or drift lines.

There is evidence of soil and debris movement (scouring) in the stream channel. Leaf litter is usually transient or temporary in the flow channel.

Wetland or hydrophyticvegetation is associated with the stream channel or flow area. Intermittent streams with deeply incised or “down-cut” channel will usually have wetland vegetation present along the banks of flood prone zone. Wetland vegetation is similar to those discussed in the perennial stream section.

The soil is predominantly brown with inclusions of gray soils (except in soils of deep sands and soils with extreme red soil color). The soil is usually alluvial type soils with loamy to sandy texture.

Streams are commonly identified as blue lines separated by three dots on USGS topographic maps and as black lines separated by two or more dots on NRCS soil maps.