An Automated Image-Based Approach to Derive Beach Grain Size Characteristics

The grain size characteristics of sandy beach sediments can vary on spatiotemporal scales. To address this, several automatic grain sizing techniques that use digital images to develop the grain size distribution curves have been developed. However, the moisture content is often not accounted for in these methods, despite its known influence on image tone and highly variable nature at sandy beaches. In this paper, a simple method to account for moisture content variation at sand beaches when applying AGS is tested. This involves a series of image preprocessing steps and a correction factor, β, that is used to convert the results of grain size curves obtained from one method so they are equivalent to another method. Previous work suggests that there is a single value of β. However, for the sands tested, it was found that β decreased as the moisture content increased. The results of this study demonstrate that the moisture content influences the grain sizes and grain size distribution characteristics derived from automatic approaches, and can be accounted for using a simple correction factor that is a function of the moisture content.