Investigation of the effect of coastral structures on the coastline of kKarasu beach in Sakarya province by CoastSat application

In this study, it is aimed to examine the change of the coastline between the years 1990-2021 and the effects of the structures built here on the 6.3 km Karasu coast to the east of the Karasu Port, which was selected as the study area by using the CoastSat open source software toolkit, which is a remote sensing method. In this context, using the CoastSat toolkit, the satellite images of the Karasu Coast between 1990 and 2021 were processed, and the coastline of the relevant coastline was overlapped by using the images from different years, which coincided with the same time, and the erosion and accumulation situation on the coast were determined. In addition to overlapping the coastlines, cross-sectional changes were also examined by taking sections from different locations along the coastline. The contribution of structures such as fisherman's shelter/harbour, groins and offshore breakwaters built on the coast to erosion and accumulation on the coastline has also been determined. In addition, the wave climate and storm climate of the region were extracted and the contribution of the changes in the wave and storm climate in different periods to this coastal line change was also discussed. As a result, the construction of the port, the construction of which was started in 1995, caused significant erosion on the coast by preventing the transport of sediments carried from the Sakarya river, and the 12 vertical groins built in 2009 to prevent this erosion caused the erosion to increase further with the effect of severe storms, and the resulting coastal erosion. It has been determined that 27 offshore breakwaters, which were built parallel to the shore, the construction of which was started in 2010 and the last one was completed towards the middle of 2016, for the purpose of preventing sand collection, and that the beach started to hold sand and the shoreline still did not reach the level of 1990 in some coastal areas, although a significant amount of sand was retained.