Considering the Risk of subsidence in south west of Tehran

Background and objective: The land subsidence is commonly associated with many risks. This phenomenon can cause substructure and natural damages, and ultimately leads to an increased risk in society and the economy. The most studies are focused on modeling and its techniques, except for two case studies in Tehran: the risk of subsidence phenomenon and the elements exposed to this risk which has not been specifically addressed. The risk assessment due to the phenomenon is necessary in order to preventive and preparedness measures. The purpose of this study is to identify the risks and the main elements within the subsidence area. Method: In this study, the subsidence area was determined according to the previous researches, and the main elements were identified; data were collected from the valid and documented sources and digitized in the GIS. The data include population and important population centers, important buildings and civil technical structures, transportation system, infrastructures and roots. The risk area map was prepared and then analyzed according to their risk rate. Field studies were used to consider the civil structures.  Findings: The demographic risk assessment (main population centers) consideration and spotted, linear and areal physical risk in buildings and urban constructions such as roads, railways, subway lines, airports, civil technical structures, urban industries and facilities, roots  and associated facilities in this section indicate the high place of important elements in the subsidence area. Conclusion: According to the digital data, 120 km of railroads, 25 km of subway lines, 2300 km of urban and suburbs roads, 21 bridges, 2 oil and fuel depots, about 44 petrol stations and 15 gas pump, 7 gas stations, 30 km of petroleum pipe, and more than 70 km of high voltage power lines, 5 districts of Tehran, 8 cities, 99 villages are located in this area. The population in the subsidence zone is 1793264 people and a large number of workers, educational, therapeutic and manufacture centers are located in this area.