Assessing Coastline Changes of Lake Gölbaşı (Adıyaman, Türkiye) Through InSAR Time Series Analysis

The coastline shape is continuously changed by natural events such as tectonic movements, subsidences, and erosion. All these changes are of great importance for understanding the dynamics of the coastal systems and their responses against events. These changes, emerging from the past to the present for various reasons, therefore form a guiding background for management and decision-making activities related to coasts in the future. In this study, Lake Gölbaşı in Adıyaman was investigated within the East Anatolian Fault Zone (EAFZ). One of the main branches of EAFZ passes directly through the Gölbaşı district. The Mw 7.8 Kahramanmaraş earthquake that occurred on February 6, 2023, caused severe land deformations, serious changes in the coastline, and land subsidence in the region. In addition to the morphological changes of the coastline, such effects as land subsidence are important in understanding how tectonic forces shape the coastal environment. Such analyses reveal the effects associated with sediment transport, erosion, long-term coastal dynamics, and changes in water levels. This information can be an important guide in predicting future tectonic events and environmental impacts and in risk management. Firstly, we performed InSAR time series analysis to obtain time-dependent deformation maps using Sentinel-1 and COSMO-SkyMed radar data. Publicly available Sentinel-1 data, operating in the C band, provides sufficient information for analyzing large-scale deformations. In contrast, high-resolution X-Band COSMO-SkyMed data, obtained from the Kahramanmaraş Supersite, enables the detection of smaller-scale changes. Additionally, optical satellite data from Sentinel-2A is employed to examine subtle morphological changes in the Gölbaşı Basin. While radar data excels at detecting specific deformations, optical data offers a broader perspective on environmental changes. By integrating these tools, the study provides valuable insights into the dynamic changes occurring in the area. The study covers a time series from February 2022 to February 2024, allowing for the analysis of both pre- and post-earthquake coastline changes and assessment of the spatial and temporal characteristics of these changes in relation to the active fault line by Lake Gölbaşı and surroundings. Our findings highlight the urgent need to address challenges related to improving living conditions, disaster risk reduction, and ecological protection. These insights are essential for developing practical and sustainable long-term strategies for natural hazard risk management.