Reflection of the Baltic Sea Lithuanian nearshore bottom peculiarities in the historical maps

Abstract

Using the bathymetry information available from historical maps, the underwater slope of the Baltic Sea in the Lithuanian area of the shore is analysed south and north of the Klaipėda harbour. For this purpose, the old depth measurements have been converted into the metric system and cross profiles of the nearshore drawn, as well as, on this basis, the diagrams for the 3, 5, 7 and 10 m depth points have been constructed. The depth data from the maps compiled in 1743, 1855, 1875 and 1913 have been analysed. These periods correspond to specific conditions of the shore zone morpho- and litho-dynamics. In 1743 there was no beach protecting the dune ridge on the Curonian Spit, and sand was driven by wind from the shore zone to the large dunes. There were no hydro-engineering structures in the Klaipėda harbour; therefore nothing impeded sand migration along the shore. In 1855 the shores of the Klaipėda channel were fixed, but there were no harbour piers yet. In 1875, the piers were freshly built and a beachprotecting dune ridge partly formed. In 1913, this dune ridge was already finished and the Klaipėda port was fully functioning with 5–6 m depths at the port gates. Conclusions are made about the former bottom relief during different stages of the nearshore evolution and about the conditions which caused its changes.