Edwards, B.L.; Schmutz, P.P., and Namikas, S.L., 2013. Comparison of surface moisture measurements with depth-integrated moisture measurements on a fine-grained beach.
Surface moisture measurement on beaches is an important component of beach groundwater and aeolian transport studies. There are several approaches to measuring beach surface moisture, but each has significant limitations. Several recent studies have used techniques that integrate moisture content over shallow depths, and this study aims to assess the utility of these measurements for characterizing moisture conditions at the sediment surface, and also to briefly comment on the usefulness of a handheld spectroradiometer for measuring beach surface moisture. Depth-integrated moisture measurements of the top 1.5 and 6 cm of sediment obtained with a time domain reflectometry probe were compared with collocated surface moisture measurements from the spectroradiometer. Results show that depth-integrated measurements overestimated actual surface moisture by an average of 2.5 and 4.4% moisture content for the 1.5- and 6-cm sampling depths, respectively. The maximum difference between surface moisture and depth-integrated moisture content was about 12% for the 6-cm depth and about 9% for the 1.5-cm depth. These results suggest that moisture measurements integrated over even shallow depths may not depict conditions at the surface accurately enough for some applications and may potentially provide a misleading description of moisture conditions at the surface. The spectroradiometer proved to be a useful method of measuring beach surface moisture (field calibration with an R2 = 0.99 and standard error of ±1.5% moisture content), but from a logistical standpoint, may not be well suited to measuring and mapping surface moisture over large areas.
