Urban Planning Issues in Earthquake Vulnerability

Abstract

Despite many advances in sciences and knowledge regarding the reduction of earthquake vulnerabilities, such as technical and management sciences, urban planning can also be considered as an effective knowledge that covers a vast society. The recent earthquake experiences have shown that a dominant portion of damages have occurred as a result of neglecting urban planning principles and criteria. The design of urban structure and form, spatial distribution of urban land use and road networks are some urban planning issues that can reduce earthquake vulnerabilities. In the context of urban planning, vulnerability issues and indicators can be considered in vulnerability possibilities by natural and artificial factors, emergency rescue during and after the earthquake, emergency aids and post earthquake reconstruction. The location of urban activities is a very important issue in land use planning. Population and construction densities are challenging issues in urban planning as a whole. While higher density can be considered as an efficient plan in the context of sustainable development, it can be inefficient in the context of earthquake vulnerability. Higher density may result in vast human damages because of the problems in emergency rescue and aids. This research has tried to examine urban planning principles and criteria in Farahzad region, located in the north-west of Tehran. Historically, Farahzad has been an organic and village-based district that is now an internal district of Tehran. The district is located in an inclined area and in the vicinity of one of the Tehran’s faults. Most buildings are deteriorated and the road network is deficient. All these characteristics indicate that Farahzad is a vulnerable area in Tehran. It is notable that there are many similar areas in Tehran that are vulnerable to earthquakes. Moreover, Iran is a country located in the global earthquake zone with many historical outbreaks. Technical methods including GIS (Geographical Information System) and AHP (Analytical Hierarchy Process) have been used to determine probable earthquake vulnerabilities. The results of research show that increasing the amount of variables such as land slope, population and construction densities, building age and distant from open spaces, can increase the amount of vulnerability. All these negative indicators were seen in Farahzad region. In contrast, increasing some other variables can reduce the vulnerabilities, including distance from faults, lot areas, access based on road wideness, and harmonies in adjacent land use. Although the reduction of earthquake vulnerability should be considered on the basis of many aspects, the process of urban planning can be seen as the most effective factor. The results indicate that consideration and decision taking based on only one variable can not be effective. It is necessary that a complex system of variables, principles, criteria and indicators must be taken into account in the process of urban planning in order to reduce earthquake damages. In this regard, dangerous areas must be determined; guidelines for land subdivision must be enacted; sufficient open spaces must be allocated for emergency rescue and aids; and unsuitable land uses must be transferred to outside of residential areas.

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