PROPERTIES OF VARIOUS SEDIMENT SAMPLING PROCEDURES

Several issues regarding the sampling and analysis of bed material from gravel bed streams are addressed in this paper. The need to convert surface samples into volumetric equivalents, and methods to do so, are explained. It is found that most surface samples are unique and, thus, are not directly comparable. Particular attention is paid to areal sampling with clay and with wax. The areal-to-volumetric conversion of samples removed from different sediment structures is also considered. Criteria are proposed for determining the minimum dimensions of unbiased volumetric samples. These criteria can be used to determine the minimum area of an areal sample. The minimum depth of a volumetric sample is shown to be larger than the depth of most surface layers. Thus, a surface layer can not be sampled volumetrically. A technique is presented for sampling a wide size range of underwater surface particles. This technique has been tested in the field and found to provide good results.