Discussion of: Steven H. Hill and Patrick McLaren, 2001. A Comparison between Log-hyperbolic and Model-independent Grain Size Distributions in Sediment Trend Analysis (STA®). Journal of Coastal Research, 17(4), 931-935.

In a recent paper, HILL and McLAREN (2001) have compared the performance of two sets of descriptive grain-size statistics in predicting sediment transport directions. The one set makes use of "model-independent" textural parameters (mean, sorting and skewness) generated directly from the raw grain-size data, the other uses the same statistical parameters but in this case derived from "log-hyperbolic" estimated curves fitted to the same raw grain-size data. Both sets of statistics correctly predicted the direction of transport with essentially the same statistical significance. HILL and McLAREN (2001) conclude that the use of the log-hyperbolic distribution provides no advantage to the application of their STA® procedure. We are writing the present discussion (a) to elucidate the term "descriptive statistics" in relation to the log-hyperbolic Probability Density Function (PDF) and the so-called moment statistics and (b) to express our opinion on Sediment Trend Analysis (STA) and how it should be used in sediment transport studies.