Ground subsidence in plains around Tehran: site survey, records compilation and analysis

Abstract Ground subsidence has been occurring in the southern areas of Tehran in the former 25 years. This phenomenon influences a 525 km2 area with a maximum measured value of 2530 mm. Subsidence rate varies in different locations, and has a maximum rate of 360 mm/year in some areas. Existence of a thick layer of clay makes this region more susceptible to subsidence. Moreover, Tehran has been experiencing drought through these years which has resulted in decrease of groundwater level. This paper concentrates on variations of ground surface level in Tehran and Shahriar plains during 1992–2010, and studies its relationship with groundwater elevation changes in this period. Changes of ground and groundwater level are modeled via ArcGIS for several different time intervals. Current study reveals that in some locations, other factors including subsurface erosion, presence of old aqueducts, drainage of organic soils, and soil removal are more troublesome compared to groundwater elevation drawdown. In addition, site investigation is performed to study the occurrence of ground collapses, regional settlements, cracks in roads and buildings, and well-casing protrusion