URBAN SPRAWL AND FERTILE AGRICULTURAL LANDS IN IRANIAN CITIES (CASE STUDY: TEHRAN AND KARAJ)

The phenomenon of disproportional expansion of urbanized areas into undeveloped area or "urban sprawl" has become a very a remarkable characteristic of urban development worldwide in the last decades. Urban sprawl is the popular media as the source of numerous social, environmental, and economic ills. One of the most evident consequences of urban sprawl is destroying agricultural lands around cities. One of the extreme expanded cities in Iran is Tehran megalopolis and cities around it. Tehran is expanding in all dimensions especially toward western side where Karaj city is located. The area of study for this research is Tehran and Karaj cities where the event of urban sprawl is happening. Materials used for achieving goal are aerial photographs, satellite images, thematic map of degree of soil and GIS software. The result of analysis shows that Tehran area has expanded from 10000 in 1956 to 80835 hectares in 2006. Area of Karaj city increased from 125 to 26000 hectare in the same period and the population density of two cities together decreased from 116 to 43 people per hectare. Sixty five percent of areas of these two cities are consisted of good fertile agricultural lands with irrigation potential. Twenty four percent of this land (14900 hectares) is classified as rank or class 1, 38.1 percent (23725 hectares) has rank 2, and 37.9 percent (23605) has rank 3 in terms of fertile land. Based on soil class and potential of production of wheat, it is estimated that if urban sprawl and expansion of these cities decreased or the direction of expansion changed to unfertile lands (class 4, 5 and 6), and the cultivation of land had continued, 270,000,000 kilos of wheat could be produced yearly. So, urban sprawl is seen as one of the potential challenge to urban sustainable development and cannot be urban sustainable form.