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The following was copied from the Water Quality section of the Gualala Basin Profile in the May 1, 2002 version of the report, pertaining to the use of Knopp (1993).

Knopp (1993) measured a variety of instream parameters on 60 North Coast streams within Franciscan geology.  The watersheds were divided into three categories based on relative upslope disturbance and erosion potential:  Index (little or no land use in the prior 40 years), Moderately Disturbed (recent land management, good stream course protection, avoidance of unstable areas), and Highly Disturbed (recent land management, large areas of disturbed soil, poor stream course protection, inconsistent avoidance of unstable areas).  Knopp found a significant difference in median particle size between the Index reaches and those of Moderate and High disturbance.

Median particle size data were available from Gualala Redwoods Inc./Gualala River Watershed Council and Coastal Forest Lands monitoring at 38 low gradient sites (<2 percent slope) in the Gualala Basin from 1995-2001.  However, those sites were predominantly less than 1 percent slope, and Knopp used sites of 1-4 percent.  Additionally, the analysis provided in Knopp (1993) does not break down the Franciscan geology into sub-categories.  For those reasons, the Knopp (1993) relationship of median particle size to watershed disturbance was not used.  However, a workgroup is being developed to evaluate Knopp’s raw data, re-site the current GRI/GRWC monitoring locations, and work towards building upon and improving the work that Knopp started.

Bob Klamt

June 1, 2002