Abstract

Data from 17 studies of stream-pebble rounding were analyzed by computing simple correlation coefficients and regression equations for distance and roundness in individual streams Of 30 cases examined, 20 showed significant downstream increases in roundness. In 13 of these 20 eases the downstream trend was described better by logarithmic or semi-logarithmic functions than by linear ones. Studies employing the Wadell-Krumbein measurement technique produce regression lines with higher Y-intercept values than do those employing Cailleux and related techniques. Regression-line slopes produced by the two methods. however, are more comparable. Slope values are also less likely than Y-intercept values to be affected by differences in operators and initial roundness values; hence, regression lines from different streams are best compared with respect to their slopes rather than their Y intercepts. Slopes tend to be steepest for limestone, most gentle for quartz and quartzite, and intermediate in steepness for other lithologies. A comparison of these slopes with those computed from Kuenen's (1956) experiments on rounding in a pebble-bedded circular flume suggests that the flume is comparable to or better than streams in rounding effectiveness.

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