Evaluating the Vulnerability of the Urban Fabric of District 18 of Tehran under the Influence of Land Subsidence using ANP and GIS

Due to the uncontrolled abstraction of groundwater resources in the last half century, the water level of groundwater aquifers in most plains of Iran has decreased sharply. Sharp drop in groundwater levels is the main cause of land subsidence in Iran. Land subsidence has the potential to cause a major human catastrophe, and if it happens, it will expose agricultural lands, urban fabric, vital arteries, and many other environmental aspects to extreme vulnerability. This study evaluated the vulnerability of urban fabric in District 18 of Tehran regarding the influence of land subsidence. The spatial study was carried out by implementing an analytical model in three steps. In the first step, the indicators of vulnerability of urban tissue affected by land subsidence were identified and classifiedbased based on three criteria of physical and demographic, access and proximity to high risk centers. In the second step, using a questionnaire and expert’s ideas, the priorities of urban tissue vulnerability in relation to land subsidence were identified and based on the network analysis process, the weight of each criterion was determined. In the third step, the weight obtained from the ANP model was applied to the spatial layers of the region in ArcGIS software. The results of model implementation showed that a high percentage of District 18 have features such as worn texture, buildings with low structural strength, very low building quality, high population and construction density and are prone to high vulnerability. Moreover, Zone 1 with 96%, Zone 2 with 88.5%, Zone 3 with 90.4%, Zone 4 with 85%, and Zone 5 with 92.3% have high vulnerability. About 90% of the total buildings constructed in District 18 of Tehran are affected by land subsidence in a highly vulnerable area.