The following report presents selected study results that are relevant to regulatory water typing of non-fish-bearing streams in northwestern Washington. It was developed to make this information available prior to finalization of permanent Forest Practices Rules, expected to occur in winter 2000/’01. More specifically, results describe the distribution of perennial and seasonally flowing reaches, the key attribute distinguishing Type 4 waters, which require partial buffering during timber harvest, from Type 5 waters, which do not. A subsequent report that covers this and other issues related to the implementation of new rules governing protection along non-fish-bearing streams will be written and made available in early 2001.
Among the primary objectives of this study was evaluating the applicability of the Emergency Rule default criteria for defining the upper extent of Type 4 waters in the northwest Cascades. For all areas west of the Cascades (exclusive of the coastal spruce zone), the present Emergency Rules (March 20, 1999 version) define the Type 4/5 break as the most upstream point of perennial flow. Except in cases where a distinct “perennial initiation point” is apparent, perennial flow is assumed to occur where the contributing basin size exceeds 52-acres (see WAC 222-16-010 – “perennial initiation point” definition). Concerns regarding the widespread applicability of the 52-acre threshold arose primarily because the data supporting that threshold were collected within southwestern Washington only (Mike Liquori, geomorphologist, International Paper Company, personal communication). The need for local validation of the default acreages was recognized in the Forests and Fish Report, which indicates that basin size thresholds are “subject to review through adaptive management”
Veldhuisen, C., 2000. Preliminary Results and Recommendations from the Northwest Cascade Type 4-5 Stream Study. Skagit System Cooperative, La Conner, WA. pp. 7.
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