Changes in the relative values of radionuclide content with respect to shallow subsurface depth of intertidal estuarine and coastal beach sands, from east and west coast localities near Auckland, New Zealand, were studied using a high-purity germanium γ-ray detector. It was found that differences in γ-ray activity from the natural distribution of radionuclides varied up to 35%. This permitted detection of grain size differences as a result of hydraulic separation and sorting processes. Grain size measurements on the same samples were also made using a laser sediment size analyzer. Comparison between the γ-ray and the laser scattering methods of grain size determination suggests that in these nearshore systems the former is a more sensitive measure of textural variations with sub-surface depth in these sandy sediments than the latter. The γ-ray technique can be relatively rapid and involves little sample preparation. It may warrant wider application.