Sampling Heterogeneous Deposits in Gravel-Bed Streams

This is the authors' abstract. We don't add key points for this paper.

The methodology of combining subsamples into a single “composite” sample representative of an entire river reach is examined. Current methods of characterizing the overall grain-size distribution of a river reach are inadequate because they either require enormous amounts of material to be collected, are inherently biased, or fail to describe the local variations occurring within the sampled region. These problems can be overcome by employing the grid-by-number sampling technique. Criteria for obtaining an unbiased grid composite sample as well as its overall accuracy are provided. It is proposed that local variations in a river reach's grain-size distribution can be located by comparing the arithmetic means of adjacent subsamples through the use of statistical hypothesis testing. By systematically comparing the arithmetic means of adjacent subsamples throughout the area of interest and using a moving windows approach to locate sudden changes in a sediment's grain-size distribution more precisely, the local variability of the river reach can be described adequately.