Foredune Defending Role: Vulnerability and Potential Risk Through Combined Satellite and Hydrodynamics Approach

The paper presents an approach to assessing potential risks for coastal areas, where the foredune acts as the first and main line of defense against storm surges. The local correction technique for satellite data via morphodynamics and hydrodynamics features, applicable for the southern part of the Baltic Sea was developed. The proposed combination of regionally adapted height of the wave run-up and the surge height made it possible to clarify the width of the beach through analyzing ESA Sentinel-2a satellite images. Using digitized shorelines from ESA Sentinel-2a imagery as a reference, together with the results of modeling the near-hydrodynamic conditions, a study of the beach width dynamics between measurements was performed. This is due to the regularity of satellite data being affected by cloud cover and the period of circulation. Identifying hot spots on the shore made it possible to establish areas with a significant excess in the repeatability of small dry beach width and, correspondingly, the erosion rate. The hot spots were detected within the Curonian Spit protective dune ridge, identifying the vulnerable areas, which are able to serve as breach points to flooding. The hydrological analysis of the flood zones under storms of varying frequency was performed, and predictions were made regarding the regional sea level rise by BACC and Team (2015) regional climate analysis. The work shows the possibilities of combining hydrodynamic and hydrological modeling, satellite observations into a single forecasting and assessment system, which allows to analyze and model risks of various origins. The results obtained can significantly improve the existing models or become the background for the integrated coastal zone management system, especially in protected natural areas.