Detecting surface moisture in aeolian environments using terrestrial laser scanning

Surface moisture plays a key role in determining erodibility of sandy and dusty surfaces in semi-arid and coastal environments. Where aeolian processes are active, sedimentation patterns may rapidly change the soil moisture on a thin veneer of the surface that determines sediment entrainment. Here we present terrestrial laser scanning (TLS) as a promising method for detecting moisture at high temporal and spatial resolution within the range where aeolian transport is possible and illustrate its applicability using playa and beach case studies. TLS instruments are active sensors that record the return intensity (or backscatter) of a laser pulse. This signal intensity is influenced by both distance and surface properties. Calibration relationships are outlined that correct for both distance and moisture and explore the influence of grain size and mineralogy. We also show that by normalising intensity using a dry surface, the resulting relative ratio infers changes in moisture patterns and is a useful alternative when sediment calibrations are not available.