Detection and characterization of aeolian sand strips on the beach using permanent laser scanning

Abstract

Aeolian sand strips are bedforms that often form on the beach during high wind events. The sand strips can move across the beach resulting in sediment transport, but these sediment fluxes have not yet been quantified. Permanent laser scanning (PLS) provides an opportunity to gather long-term and detailed information about sand strips. Here, we present a method that detects sand strips in PLS reflectance images and extracts their wavelength, orientation, and height. The detection method is used on a month-long hourly dataset of Noordwijk beach, the Netherlands. The average sand strip wavelength (13 m), height (3 cm), and orientation (onshore-oblique) found in this dataset are consistent with previous research. Migration rates are obtained by examining successive images of sand strip patterns. Using the concurrent sand strip height, the sediment transport rate associated with sand strips is estimated. During a single 8-hour event, a total sediment flux of 0.16 m3/m is observed of which 0.07 m3/m in onshore direction. Furthermore, the detection method is shown to be applicable to other beaches by calibrating its thresholds. This opens a new possibility for future research to use PLS to investigate the behavior and sediment transport rates of aeolian sand strips.