Monitoring observations of section of the sandy coast of the Baltic Spit dynamics

In May 2019, a research polygon was organized at the Baltic Spit shore area (South-East Baltic). The purpose of organizing this polygon was to observe wave morphodynamics of the accumulative coast. The study site is located on the open coast of the Vistula spit near the city of Baltiysk. The spit in this region is oriented from SSW to NNE with 32 degrees azimuth. The coastal zone of the polygon is characterized by a 30–35 m wide beach adjacent to the gentle (bottom slope tangent is equal to 0.016) sandy bottom slope with two sand bar systems. Sand bars are very dynamic, moving seaward and shoreward, changing shape from crescentic to near parallel to the coast over time, possibly dependent on dominant wave direction. The coastline also changes its form, varying from cuspate to straight. Regular measurements of coastal bathymetry on the study site (Figure 1) started in May 2019. In total 9 measurements were carried out during 21 months. The size of the measured area was 600 × 500 m. The depth measurements were carried out from a small vessel with the Garmin GPS Map 580 Plus echo sounder. Twenty shore-normal tacks with 30 m distance between them were made. Depth values were recorded each second, which gives around 1–1.5 m spatial resolution. Depth accuracy for such measurements is 10 cm. The bathymetry data obtained with an echo sounder mounted on the boat transom is limited to 0.5–0.8 m depth. Beach topography was obtained with the RTK GNSS system EMLID Reach RS+. Two receivers were used: one as the base and another – as the rover, which allowed to gain centimeter accuracy in the measurements. The base receiver position was located using stationary benchmarks. During one topographic survey of the beach elevation data was collected in around 250 points both in the submerged and emerged parts of the beach along 25 cross-shore profiles. Submerged part of the beach was mapped up to 1-1.2 m depth, emerged part - up to the dune cliff base. Points where the data was collected were chosen on the inflections of the landforms. The data set of this project contains ERA5 wave reanalysis data for the entire measurement period.