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Stream Protection Zone

What is an SPZ?
The SPZ is a mandated 75-foot minimum distance from a Class I stream, lake, or other water body that must be protected because of its special importance.

The function of an SPZ is to protect water quality along streams, lakes, and other water bodies. The riparian area "green zone" around streams, lakes reservoirs, springs, and seeps represents the area that stays green long into the summer months. Riparian areas usually have wet soils, high water tables, and can be identified by the presence of water-loving plants such as alder, willow, cottonwood, cedar, and spruce. Some intermittent streams and other water bodies, particularly in southern Idaho, may not show riparian areas, but they still have to be protected with an SPZ. Recognizing these areas and knowing where they are in the forest will make protecting water quality with an SPZ much easier.

The 75-foot minimum SPZ often extends beyond the riparian area "green zone." This is important when slopes near streams are steep and soils are unstable, or when the riparian area is narrower than 75 feet. Details concerning how to identify a stream, marking an SPZ. and when the SPZ should be more than the minimum are covered on SPZ Boundaries.

The forest harvesting scene above presents some of the decisions facing loggers and forest landowners. Some decisions were made correctly. Others were not. Proper on-the-ground application of BMP's requires practice and personal judgment.

What is there about SPZ's that needs improving?
Since 1985, comprehensive audits have been conducted on over 300 timber harvests across Idaho (see also Roads). Results indicated that a few SPZ's had poor overall ratings because water quality was not protected. The SPZ's were rated poorly, not because timber harvesting had occurred, but because BMP's were not applied properly, resulting in water quality damage. BMP's don't prohibit harvesting in SPZ's, but do call for care, to protect soil and water resources of the SPZ.

Specific problems cited in SPZ's included:
  • Constructed roads and skid trails within SPZ's.
  • Inadequate road drainage near streams.
  • Logging slash left in the stream.
  • Equipment operation in the SPZ's and wetlands was excessive.
  • Improper use of broadcast or pile burning in SPZ's.


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