Beach Sediment Sampling Methods

摘要

The sampling of beach sediments can be done in numerous ways and in many instances a choice of sampling method is made without considering the degree of accuracy which can be expected. Since the median grain diameter is a critical factor in many coastal engineering problems, the accurate determination of this parameter is of great importance. A standard sampling lay-out for the foreshore part of a beach profile is necessary in order to obtain a reliable estimate of the mean median grain diameter for coastal engineering application. Experiments were done on six test beaches which were selected on the basis of their different sediment characteristics. The results of different sample combinations were statistically analysed in order to determine the number of samples which is necessary to obtain a reliable estimate of the grain size within a given confidence band. The most significant conclusion which can be drawn is the recognition of two distinct grain size populations which are separated by the mid-tide line. A minimum of five samples is needed from each zone to obtain an acceptable estimate of the mean value of the median grain size. All the samples from the same zone may be combined into one composite sample to simplify the analysis. This implies that only two samples are obtained for each beach section, namely, one for the upper and one for the lower foreshore. Some sampling techniques which can be applied to simplify the sampling procedure were also evaluated. A number of recommendations with regards to these techniques are given.