Document Type : Research Paper
Abstract
Over the past two decades, several models have been used to calculate environmental vul-nerability with Approach collective decisions to mitigate the effects of the natural hazards. Location of cities and villages, and site selection of residential units, services, and indus-tries and recreation should be harmonized with expansion of geology, geomorphology, soil and climatology sciences. Therefore, without understanding their natural features, the construction of urban and rural areas and related activities associated with their spatial substrate is not reasonable. Yasuj urban area is located in narrow plains in the western foothills of the Zagros Mountains. The area of this place is about 12776 hectares and its average topographic height is about 1850 mASL. The area consists of 42 villages whose population is over 150 thousand and its city center is Yasouj. The main purpose of this study is to put stress on the theory of sustainable development in Yasuj urban areas. The study of natural vulnerability of Yasuj urban areas was performed with an emphasis on the natural and environmental structure. Methods used to analyze the vulnerability include Fuzzy logic, Analytic Hierarchy Process (AHP) and environmental indicators that were used by Geographic Information System (GIS). Based on the criteria and sub criteria of the study, the study area affected by natural features and special characteristics are threatened with some environmental restrictions and natural hazards. Due to young and active faults, the urban area shows great potential for earthquake. The probability of flood in the area increases as a result of the features of the mountain, sharp slopes, existence of several torrent rivers, relatively high amounts of rainfall, especially during the cold season. Structure and texture of alluvial plains and foothills are almost weak. In addition, the steep foothills can increase probability of hillside movements and phenomena such as the downfall of soil and rock, landslides and avalanche at snowy periods. According to the results obtained from combining various layers of environmental data layers car -ried out on the basis of analytic hierarchy process (AHP) model, it became clear that ,in Yasuj urban area, central parts of the plain have the lowest environmental vulnerability with the rise of the risk level towards the mountainous area. The study not only reveals that proximity to faults has the highest fuzzy membership degree, but also suggests that collaboration with other environmental hazards such flood risk (distance from the river), slope and land use, shows the highest vulnerability. The surrounding mountainous areas (Zagros) in Yasuj urban area which are tectonically active parts of the area have higher risk in comparison with those in the plain. Considering the results, growth and develop -ment of the city toward the mountains will encounter high vulnerability. These results corresponded with the capability of the forest parts of the mountainous areas. Therefore, the development of the city construction toward the mountain would cause sever damage to mountain ecosystems, plant and animal life. Thus, areas characterized by high vulner -ability should be protected since they have not only high potential for being risky but also are vulnerable to the development of human activities (regions of oak forests and rivers protection area). The results of this research lead the policy of regional development to decrease the possibility of environmental vulnerability. The assessment and combination of the results of the information layers studies signal the high environmental vulnerabilityin peripheral parts of urban area due to the overlapping of different natural hazards that tend toward the center of the plain. Finally, the salient point of studying the area shows that in the absence of any planning and measurement of the ecological capability of the land, development inflicts serious environmental damage, which , in turn, may harm hu -man societies in the future.
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