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Application of aerial photographs (UAV), satellite images and archive maps in investigation of morphological changes of beaches (island of Hvar, Croatia)

The island of Hvar is mostly formed in carbonates. It is the longest Croatian island, with a coastline length of 254, 2 km and an indentation coefficient of 4, 14. The rocky coast makes up the majority of the island. By means of orthophoto, satellite images analysis and fieldwork, 247 beaches have been distinguished on the island. They are mostly pocket beaches, with an average area of 258, 8 m2, and average length of 32, 66 m. The total beach length reach 8067 m, showing that beaches make up 3, 2% of the total coastline length, the rest referring to rocky coast. Studying the Zogon beach it was observed that in the period from the 1960s in the 20th century till today the beach surface reduced by 50% (Faivre and Mićunović, 2017). Consequently, twelve beaches were selected for further investigations (Fig.1). Here we search for morphological changes from the beginning of the 19th century to present day (Mićunović and Faivre, 2021). The first period was analysed using Franciscan Cadastre from 1834, where beaches were mapped as individual parcels. Their surface areas are registered in Cadastre Supplement and are expressed in the Klafter quadrimeter. The recent period was analysed by UAV. The collected data was used to generate DEM, DSM, orthophoto and point cloud. Furthermore, the period in between, was estimated using the repeat photography method which was adapted for the studies of beaches in previous research (Rajčić et al., 2010 ; Faivre and Mićunović, 2017). All analyses were made using ESRI ArcGIS Pro and Drone2Map software. The first obtained results show that surface areas of all analysed beaches decreased from 20%, up to 77% during the last ~200 years (Fig.2). This research was made with the support of the Croatian Science Foundation (HRZZ-IP-2019-04- 9445).

beach ; coastal geomorphology ; Hvar ; EAC

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