Risk Zoning of Land Subsidence Due to Groundwater Level Declining using Fuzzy Analytical Hierarchy Process (Case Study: Ardabil Plain)

Over exploitation of groundwater and exist of land subsidence evidences in Ardabil plain, demonstrate necessity of land subsidence risk zoning in this plain. The purpose of this study was to preparation land subsidence probability map and determines the high-risk areas with using fuzzy analytical hierarchy process (FAHP) model. Information layers including; geological formation, distance from the fault, rate of groundwater level decline, slope and thickness of alluvium were used as effective factors. The pairwise comparisons for criteria were done by using experts’ opinions. Obtained weights were assigned to each layer in the Geographic Information System (GIS) and land subsidence risks were calculated. The results show that this plain has 13 percent of very high risk, 20 percent of high risk, 45 percent of moderate risk, 16 percent of low risk and 6 percent of very low risk of land subsidence. Also, about 67.5 percent of the southern regions of area, due to excessive use of groundwater, have very high and high class of land subsidence risk. For verification of the results, field data of fractured pipe wells were used. The verification results show that almost 80 percent of model outputs (moderate to high risk) are consistent with field data.