Evaluation of land Subsidence in Southern Mahyar Plain Using Radar Interferometry

Phenomenon of land subsidence in recent decades has created many problems for agricultural lands، residential areas، roads and water channels in some of the plains in Isfahan province. The southern Mahyar plain is located in 50 km of southeastern Isfahan. It is one of the areas where the excessive withdrawal of ground water resources (mainly in the agricultural sector، based on available information) has substantially grown in recent years. The amount of water extracted from underground has increased from 58. 8 million cubic meters (from 217 wells) in 1369 to 85. 5 million cubic meters (from 446 wells) in 1388. The decline in water table increases the effective stress that causes consequences such as land subsidence and cracks in some parts of the southern Mahyar plain. To determine the effectiveness and ultimately to estimate the rate of subsidence، radar interferometry was used in this study. It is a reliable method to measure changes in the land surface، with very high accuracy، wide coverage and high spatial resolution. Maximum rate of subsidence was calculated at 8. 2 cm/year using ENVISAT satellite radar images in the period of 2003-2006. The results of time series analysis showed that the land surface in the zone of danger is falling as a result of a decline in water table levels at a constant rate.