This study explores the potential of joint use of terrestrial (TLS) and airborne laser scanning (ALS) to quantify rapid and spatially inhomogeneous changes to the subaerial beach and to characterize the intensity of coastal processes. This remote sensing technology that uses scanning laser pulses for acquiring high-resolution three-dimensional surface of the measured object is applied to beach segment of the Pirita Beach (Tallinn Bay, the Baltic Sea). The extent and distribution of erosion and accumulation spots are analyzed by means of creating and comparing two digital terrain models of these areas from scanning point clouds obtained in different seasons. After elimination of systematic errors the ALS/TLS combination yields sub-decimeter accuracy for height determination of the beach. The analysis reveals not only the corresponding volume changes in the study area but also several features of internal dynamics of the beach across and along the waterline that are overlooked by classical monitoring methods. The benefits and shortcomings of combining the two laser scanning methods for monitoring coastal processes and the accuracy of the results are also discussed.

Unmanned aerial vehicle photogrammetry is a surveying technique that enables generating point clouds, 3D surface models and orthophoto mosaics. These are based on photos captured with a camera placed on an unmanned aerial vehicle. Within the framework of this research, unmanned aerial vehicle photogrammetry surveys were carried out over a sand and gravel embankment with the aim of assessing the vertical accuracy of the derived surface models. Flight altitudes, ground control points and cameras were varied, and the impact of various factors on the results was monitored. In addition, the traditional real-time-kinematic Global Navigation Satellite System surveys were conducted for verifications. Surface models acquired by different methods were used to calculate volumes and compare the results with requirements set by Estonian Road Administration. It was found that with proper measuring techniques an accuracy of 5.7 cm for the heights were achieved.

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We address the possibilities of combining terrestrial (TLS) and airborne laser scanning (ALS) techniques with the classical concept of equilibrium beach profile to quantify the changes in the total sand volume of slowly evolving sandy beaches. The changes in the subaerial beach are determined from a succession of ALS surveys that were reduced to the same absolute height using a TLS survey of a large horizontal surface of constant elevation. The changes in the underwater sand volume from the waterline down to the closure depth are evaluated using an inverse of the Bruun Rule. The relocation of the waterline is extracted from the ALS scanning of elevation isolines of 0.4-0.7 m. The method is applied to an about 200 m long test area in the central part of Pirita Beach (Tallinn Bay, north-eastern Baltic Sea). The sand volume in this area exhibits extensive interannual variations. The annual gain of sand in the entire beach was about 2000 m 3 /y in 2008-2010 and the annual loss was about 1100 m 3 /y in 2010-2014. The changes in the underwater part of the beach are by a factor of 2-2.5 larger than the changes in the subaerial part.