Risk Evaluation of Flooding Due to Human Factors Using Geographic Information System (GIS), The Case Study of Tehran Province

Population growth and development of urbanism in hazard-disposed areas lead to higher vulnerability to natural disasters in civil societies. Ignoring riparian zones in construction and development and hyper-grazing and non-standard agriculture by humans have a number of direct and indirect deconstructive influences. One of the crises that threaten the cities is the flooding due to the interference of human in nature. On the other hand، by consideration of major risk reduction factors، risk of disasters that leads to catastrophes may be predicted and procedures can be conducted to avert them. This act requires preparation، development، and incorporation of various local data. Geographic Information System، as an efficient tool in analyzing the local data، can be very effective in evaluating and zoning of this hazard. Tehran province is constantly under flooding threat because of its special geographic conditions. Unfortunately، because of heterogeneous development of the cities in recent years and ignoring the principal urban planning regulations، there exist serious sewerage complications. As a result، one of the crises that threaten Tehran province is flooding due to human interference in nature. Therefore، in order to control and decline these disasters، policies regarding land use allocation in riparian zone and watercourse، transport network development، and soil blowing control، should be adopted based on maps and probable hazards in riparian zones and watercourses. In this research، flooding risk due to human factors in Tehran province is investigated using ArcGIS Software، and then the extracted data are analyzed. To do so، the effective factors on flooding due to human factors، and preparation of contingency maps for vulnerable locations، are recognized. In this approach، initial data are provided first، and then the required layers are extracted from the data structure table in ArcGIS Software. Subsequently، the layers associated with effective coefficients in flooding due to human factors، such as land use layer، access network in riparian zones layer، and amount of soil blowing layer، are mounted on each other and contingency and vulnerability are generated separately. After that، flooding due to human factors and contingency maps were generated separately and factored based on their effects on probability and intensity of the disaster. The calculated layers are mounted on each other، leading to the final map، which shows the flooding possibility due to human factors mostly due to violating the riparian zones. Analyzing the flood hazard map of the province demonstrates that most of the residential constructions and even substructures like transportation networks are built in riparian zones and watercourses، having very high risk of flooding. This happens because urban planning and land use regulations and standards are ignored، and in case of a disaster، there would be a huge financial and life loss. Because of this، crisis management and vulnerability reduction of areas with high and very high risks require appropriate and practicable planning and policies such as reduction in density of human residences، transportation network، and facilities in riparian zones and watercourses، creating constructional laws for riparian zones، and following the agricultural standards.