Hey, John, I recalculated D50 for all Boulder segments with slope < 4%.
but here is slope and area for all river segments:
In the map below, the blue river segments are those with area > 107 square meters and slope < .04. The red segments match the outlier points with area < 107 and slope < .04.
Plugging in your constants and converting to arc/info notation, the Boulder values are
calc d50_2003 = ( ( 7.4 * ( area ** 0.24 ) * slope ) ** 0.4 ) / 35.043974Thanks to your help with subtraction, the results look plausible, but they are still substantially different from 1998. So?
April 15 b&w postscript plot files
This shows the stream density (from DNR) of Boulder River v. calculated streams on the Hoh.