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Recent developments in unmanned aerial vehicles (UAVs) have resulted in high-resolution digital elevation models (DEMs) of vulnerable coastal environments, including beach–foredune topography. If performed repetitively, they can offer an excellent tool to determine the spatial and temporal changes in the sediment budget, which may be required for proper land management. However, the quality of a UAV, slope parameters, and vegetation significantly influence DEM accuracy. The aim of this study is to compare precise GPS-RTK transects across a section of the South Baltic coast in Poland with those obtained from a DEM based on high-resolution and high-accuracy images obtained by a wind-resistant, high-quality fixed-wing UAV during beyond visual line of sight operation (BVLOS). Different land cover classes, slope inclination, and general curvature, as well as surface roughness, were taken into consideration as possible factors influencing the uncertainty. The study revealed that marram grass greatly affects the accuracy of the UAV-derived model and that the uncertainty of the UAV-derived DEM increases together with increasing slope inclination and, to a lesser degree, with increasing general slope curvature. We showed that sediment budget determinations with the use of a UAV-based DEM are correct only where grass cover is sparse, in our study, up to 20% of the area.

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Tsu nami de pos its have not pre vi ously been re corded along the south ern coast of the Bal tic Sea. The re sults of pres ent research pro vide ev i dence of high-en ergy event lay ers that oc cur on the bot tom of two hemi spher i cal hol lows cut into glaciolimnic silt and glaciofluvial sand and gravel of Late Weichselian age. The event de pos its are rep re sented by poorly sorted ma rine sand with ad mix tures of peb bles and allochthonous biogenic de tri tus: ma rine, brack ish and oc ca sion ally fresh wa ter shells and shell de bris of bi valves and snails, plant macrofossils from the nearshore zone, shreds and lumps of peaty ma te rial, gyttja and organogenic silt, lumps of char coal, wood pieces and tree branches and trunks. All these fea tures are com monly con sid ered in dic a tive of tsu na mis. The age of the biogenic de tri tus found in the tsu nami layer ranges from 6,630 to 10,390 cal. yr BP, whereas the old est gyttja cov er ing the event lay ers is 6,600 cal. yr BP old. This means that the tsunami oc curred be tween 6,600 and 6,630 cal. yr BP. Var i ous causes of the tsu nami event are con sid ered, in clud ing the impact of me te or ites within the coastal plain and the lit to ral zone of the south ern Bal tic Sea.