Monitoring and Prioritizing Control Solutions for Land Subsidence in Khonj Plain, Iran: An Integrated Approach of SBAS Time Series Analysis and AHP Model

Abstract

Land subsidence is a critical environmental hazard in arid and semi-arid regions, primarily associated with excessive groundwater extraction. Khonj Plain, in southern Fars Province, Iran, has experienced a marked decline in groundwater levels due to intensive agricultural activities in recent years. However, no comprehensive study has monitored the subsidence rate or identified critical hotspots in this plain. This study aimed to prepare a land subsidence map of Khonj Plain using the SBAS time-series method and 21 Sentinel-1 radar images acquired from January 2020 to January 2022, and to identify and prioritise effective control solutions using the Analytic Hierarchy Process (AHP) based on the opinions of 20 experts. The results showed subsidence ranging from 31 to 218 mm during the two-year period, with an average annual subsidence rate in critical areas exceeding 109 mm/year. The highest rates of vertical displacement were concentrated in two main areas: south of Khonj city and between Dehno and Hosseinabad villages. These areas coincide with Quaternary alluvial deposits with thick fine-grained sediments and intensive agricultural land use. The AHP results indicated that hydrology had the highest cluster weight (0.42), followed by agriculture (0.27), economic (0.19), and management (0.12). Among individual solutions, banning new well drilling and sealing illegal wells (H2) and utilising groundwater resources in balance with recharge (H1) ranked highest, with weights of 0.143 and 0.126, respectively. The findings provide a scientific basis for water resources management and land-use planning to control and mitigate land subsidence in Khonj Plain.