Caspian rapid Sea level fluctuation and intensity of shorelines displacement in the Gomishan Lagoon

Coastal displacement due to hydrodynamic factors and changes in sea level has serious impacts on adjacent ecosystems, economic infrastructure, and human communities. Rapid fluctuations in the Caspian Sea level have created unstable conditions for coastal environments since the twentieth century. This study aims to evaluate the amount of shoreline displacement and Morpho- logical changes in the shoreline at the location of the Gomishan wetland between 1995 and 2019 and its impact on this international wetland. To this end, by processing Landsat satellite Images in the mentioned years using the Normalized Difference Water Index (NDWI), the water body was separated from non-water to extract the shoreline. The results show a significant displacement of the shoreline ranging from -136 to -1072 meters downstream of the Gorganrud River estuary in the southern region and a forward displacement of the shoreline inside the sea from 135 to 7781 meters, with most of the displacement occurring in the northern section. The studied area was classified into three groups based on the shoreline displacement (high, medium, and low). The results show that the northern part of the Gomishan wetland experienced the highest amount of shoreline displacement, and the amount of shoreline displacement gradually decreased in the central and southern regions. Additionally, the results show a significant relation with the period of decreasing the Caspian Sea level during the study period.