Morphological changes in the beach-foredune system caused by a series of storms. Terrestrial laser scanning evaluation

Abstract

The shallow sandy shores of the Curonian Spit (the Russian part of the South-Eastern Baltic) are regularly exposed to storm activity. The Spit foredune serves as a barrier to protect ecosystems and settlements from dangerous hydrometeorological phenomena. Consecutive number of storms resulted in intensive erosion of the foredunes as well as in breaking and flooding of the territories. Quantitative assessment of the beach-foredune system was carried out using terrestrial laser scanning technology. The evaluation included pre-storm measurements of the system condition, as well as a series of post-storm assessments in 2014-2016. This allowed us to obtain multi-temporal, highprecision digital models of the coastal topography for further morphodynamic analysis. The foredune experiences the worst slope erosion changes under the cumulative effects of several events. Prolonged exposure to strong winds of open points, wind surge and waves leads to erosion of the beach, losses in morphology and a shortage of sands. As a result, the dissipation of the wave energy decreases, which may cause erosion of the foredune in some upcoming storm events. This shows that the sequence and timing of various storm events play an important role in the variability of the entire system. The use of high-precision distance measurement tools allows to carry out accurate estimates of sand dynamics in the onshore systems. Such assessments provide information on the morphological response to repeated storm events, including variable exposure parameters for taking effective shore protection solutions.