Monitoring and Analysis of Subsidence Risk in Shahrekord Plain Using Radar Interferometry

Extended Abstract



Introduction

Land subsidence is one of the serious environmental and social challenges that has gained significant attention in recent years, particularly in the arid and semi-arid regions of Iran. This phenomenon, caused by both natural and human factors, refers to the lowering of the Earth's surface due to various reasons, including excessive extraction of groundwater, mining activities, and natural factors such as earthquakes and rock dissolution. Land subsidence can have dangerous consequences for infrastructure, ecosystems, and water resources, posing a serious threat to sustainable development and daily life. This article provides a deeper examination of land subsidence in general, as well as the causes of this phenomenon in Iran, its consequences, and potential preventive measures. So far, in the Shahrekord Plain, there has been no study on calculating the phenomenon of land subsidence and groundwater level changes using radar interferometry time-series analysis, which has proven to be highly effective for structures and settlements. The overall objective of this research is to determine the level of risk and precise subsidence in the region using radar interferometry. By identifying the causes and damages to buildings, the study aims to provide practical and fundamental solutions to control and prevent land subsidence based on its results.



Methodology

The research is designed with a quantitative approach based on radar interferometry technology, which enables the measurement of land surface changes with millimeter accuracy. The research methodology is based on processing Sentinel-1 satellite data over the period 2019-2023 using the specialized SARPROZ software.

To evaluate the land subsidence rate in Shahrekord, the Synthetic Aperture Radar Interferometry (InSAR) technique was used. In fact, the Synthetic Aperture Radar Interferometry technique is a combination of the interference of two electromagnetic waves on the Earth's surface and the Synthetic Aperture Radar (SAR) technique. This technique uses the phase information from two radar images and calculates the amount of crustal displacement by computing the phase difference. Subsequently, in order to assess the relationship between groundwater level decline and land subsidence, groundwater level maps of the study area were prepared using geostatistical models in the Surfer software. In the final stage, to evaluate the relationship between subsidence and the extraction process, the subsidence map and the water level map were aligned in Google Earth software.

This method allows for continuous and precise monitoring of land surface changes on a large scale without the need for physical presence in the area. Radar interferometric data is integrated with ground information including groundwater levels, precipitation, geotechnical specifications, and well data to provide a comprehensive analysis of the controlling factors of subsidence. Advanced statistical analyses including multivariate regression, correlation analysis, and spatial analysis methods have been employed to identify patterns and causal relationships.





Results and Discussion

The collection of field data, local visits, and validation of results with ground data also constitute an important part of the methodology of this research. The results of the research confirm significant subsidence in the Shahrekord plain, with a maximum subsidence rate of 77 millimeters measured over the four-year study period. The spatial pattern of subsidence indicates that the central parts of the plain, with an annual subsidence rate of more than 5 centimeters, are the most vulnerable, which is far beyond the international permissible limit of 2 millimeters per year. Correlation analysis has shown a strong and significant relationship between the drop in groundwater levels and the rate of subsidence, with a correlation coefficient of 0.87 calculated. A nine-year reduction in precipitation and ongoing drought has played a decisive role in exacerbating this phenomenon, such that in areas with the lowest precipitation, the highest subsidence rates have been observed. Analysis of the influencing factors shows that the combination of groundwater level decline.



Conclusion

The research results confirm significant subsidence in the Shahrekord plain, with a maximum subsidence rate of 77 millimeters measured over the four-year study period. The spatial pattern of subsidence indicates that the central parts of the plain, with an annual subsidence rate exceeding 5 centimeters, are the most vulnerable. This rate far exceeds the international permissible limit of 2 millimeters per year.The results show the exploration of stability and steady state models for studied barchan dunes. The stability model was involving the input and output of energy and material in the barchan system that eventually is formed a flow structure. This structure is representing the stability and equilibrium of barchan system in time. Also, the obtained results from investigation of steady state index show the barchan dunes, with annual displacement rate more than 12 meters, have the maximum number and highest rates of displacement, and have the lowest steady state. Thus this group is demanding the more attention and planning requirements for stabilization of quicksand and environmental management of mobile barchan dunes.