Modelling-Based Assessment of Land Subsidence in the Abhar Plain, IRAN

In this paper, the subsidence modelling of Abhar plain, Northwest of IRAN, was performed by developing the SUB sub-model in the numerical code structure of the MODFLOW Finite Difference. In order to measure the quantitative model of groundwater flow in unsustainable conditions, 70% of piezometric data during the period (2010-2020) and PEST automatic code were used and 30% of the piezometric data during the period (2014-2017) were used for validation. That data was chosen, as it was complete and unused. An examination of the vertical changes in the structure of the earth's crust showed that during the ten-year period, the aquifer had a subsidence of 34 cm. In the study of complementary fuzzy model using gamma overlap between effective layers with the maximum occurrence of correlation of linear regression of subsidence points, it was found that the analysis of land use effect corresponds to the interpretation of subsidence changes of fuzzy model. Based on results, urban usage as 4% of the aquifer surface area accounts for 26% of the subsidence event; as 42% of the aquifer surface area, in addition, agricultural usage and garden lands constitute 56% of the subsidence event; constituting 54% of the saturated aquifer surface area, finally, arid lands only account for 19% of vertical subsidence changes in the aquifer structure. Aimed at preventing the subsidence and its destructive effects, the method overlay weighted of layers created by using gamma operator in fuzzy model for zoning as a new technique in calculating land subsidence rates by land use type, can be used in identifying more susceptible lands of subsidence.