Iran's Subsidence and Sinkholes

Subsidence is defined as a type of ground failure characterized by nearly vertical deformation, or the downward sinking of earth materials. It often produces circular surface pits, but it is possible to produce linear or irregular patterns of failure. Iran faces a great amount of subsidence. Tehran, Iran's capital which contains about 14 million people, is subject to ground water deformation. Tehran's ground water supply has been minimized over the past decades, partly due to immigration and rapid population growth, and partly due to increased extraction. The increasing demands upon ground water resources due to expanding metropolitan and agricultural areas are a serious challenge, especially in semiarid and arid regions. Decades of unrestrained groundwater extraction for domestic, agricultural, and industrial use have resulted in a dangerous decrease of this valuable resource. Ground water basins in central and northeast Iran often face the problem of declining groundwater levels, often due to the destruction of aquifers. There are many other locations in Iran that face subsidence, such as Rafsanjan, Mashad, Kashmar, and more. The technique of Interferometric Synthetic Aperture Radar (InSAR) is suited to monitor elastic and inelastic response of aquifer systems to changes in ground water levels, providing geological insight into the roles of geological structures and lithological parameters in plain aquifers. The InSAR's satellite is most sensitive to vertical motions, which is appropriate for measuring land subsidence. The InSAR- derived subsidence map show important information for the mitigation and land subsidence hazards in Iran and can possibly help improve the management of groundwater resources.

In the period of 1989 through 2004, there has been a large number of collapsed sinkholes in the Famenin and Kabudar plains, Hamdan province, west of Iran. Collapsed sinkholes develop when surface or near surface material collapses into an underground cavern. As subsidence features, these sink holes can develop into spectacular collapse structures. The Famenin and Kabudar plains are facing a serious deficiency in ground water resources. This is due to the increasing demand for drinking and agricultural products with rapid population growth and agricultural development. Because these sinkholes bring many risks such as the Hamdan electrical power plant, threatening human lives due to catastrophic subsidence, and destroying farm lands, Iran has assigned researchers to assist the hazard. In December of 2005, The West Regional Water Authority of Iran organized a conference on the sinkhole hazards. Database of sinkholes and knowledge of the mechanism has been made in order to manage the hazard.

Sources:
http://onlinelibrary.wiley.com/doi/10.1029/2008GL033814/pdf

http://conference.khuisf.ac.ir/DorsaPax/userfiles/file/pazhohesh/zamin%20mashad/91.pdf

https://www.researchgate.net/publication/226306815_Hazards_and_mechanism_of_sinkholes_on_Kabudar_Ahang_and_Famenin_plains_of_Hamadan_Iran