A geospatial approach to understanding sinkhole formation in Akgöl Wetland, Türkiye

Abstract The over-extraction of groundwater for agricultural purposes in the Konya Closed Basin (KCB) has led to land subsidence and new cover collapse sinkholes (CCS) in regions like the Akgöl Wetland (AW), where such occurrences were previously absent. InSAR data from 2014 to 2023 indicate that the average annual subsidence in AW varies between 15 mm/year and 30 mm/year. Alarmingly, in specific locations, the cumulative subsidence has reached 230 mm over nine years. The significant subsidence observed in the southern region of the study area aligns with a fault line between limestone and alluvial deposits. Furthermore, several bedrock collapse sinkholes (BCS) are seen in the limestone south of the lake. The orientations and alignments of the long axes of these dolines are pointed towards the region where recent CCS has developed. This may suggest the existence of an ancient bedrock collapse structure beneath the alluvium. During intense rainfall, the former lake region experiences transient flooding, with surface water draining southward, converging at the fault line and concealed BCS beneath the alluvium. This flow has induced CCS formation due to the concentration of groundwater flow within the intersection zone. The results of this study emphasise that it is necessary to develop integrated hazard mitigation plans, considering hydrology, lithology, structural geology, remote sensing, and geomorphology to address issues such as the KCB and other global problems.