عنوان مقاله [English]
Urbanism rapidly expansion and development during last four decades has caused spreading of the physical space of cities and destruction of surrounding lands while most of them are high quality agricultural lands and gardens. The urban sprawl or low density development of cities has been one of the main urban debates because many cities have faced with its negative impacts. The term of “urban sprawl” is highly politicized, and almost has negative connotations. It is criticized for causing environmental degradation, intensifying segregation, undermining the vitality of existing urban areas and attacked on aesthetic grounds. This term has also become a rallying cry for managing urban growth. Iranian cities also have experienced this phenomenon and many researches have been conducted in this field in last few decades. This term has translated to horizontal urban expansion and uncontrolled growth in Persian language. Generally, urban sprawl refers to uncontrolled and disheveled development of suburbs. Webster’s dictionary has defined sprawl as disheveled urban development. During the last decades, rapid peace of urbanization has led to physical development of cities and their surrounding areas and resulting in destruction fertile agricultural lands. The major consequences of urban sprawl include inflated infrastructure and public service costs, energy inefficiency, spatial disparity in wealth between cities and suburbs, alteration of ecosystems patterns and processes, loss of farmlands and open spaces, increase in temperature, increase in fossil fuel consumption and emissions of greenhouse gases, reduce in water quality and quantity, and more unpleasant and monotonous suburban landscapes. The Gradual expansion of city to agricultural and orchards lands has led to many environmental impacts. One of the major problem of Iranian cities is urban sprawl and its negative impacts such as development of informal settlements, deterioration of agricultural land, overpopulation in the cities, inability to meet some of the services and in cities, disruption of physical tissue, environmental problems, especially pollution and the chaotic urban landscape. Assessing the city development process and understanding of land use changes patterns are essential to appropriate planning. This paper aimed to evaluate city sprawl and its impact on land use changes based on remote sensing and GIS techniques. Data have collected using documentary and field studies. Landsat TM satellite images for the years 1984, and 2012 were obtained from United States Geology Survey (USGS) and were utilized in this paper. Supervised classification fuzzy methods based on the severity of compliance was used to classification and changes of land use were analyzed using cross-tab model. The urban sprawl over the period of 1984 to 2012 was determined using Shannon’s entropy and Holdren’s model along with GIS tools. Shannon’s entropy is one of the commonly used and effective techniques for monitoring and measuring of urban sprawl. CA-Markov Model as a combined mode was used to simulate urban growth for future 10 years. The analysis of LULC changes has revealed that from 1984 to 2012, the built-up area has increased by greater than 6.401 hectares that is more than 43 percent. To analyze the urban sprawl, we need to demographic data and built up area. Population data is acquired from the Statistical Center of Iran and the built up area is calculated through the classification of satellite images. Findings from analyzing urban sprawl by Holdern model revealed that population factor has greatest impacts on Karaj development over the last 28 years. This factor has neutralized hideous urban growth. The amount of Shannon’s entropy of the city was close to the maximum value (2.302), showing an increase hideous urban growth in the study period. Karaj metropolis has dramatically increased in a short time due to proximity to Tehran as well as concentration of industries and services. Factors such as natural growth of population and immigration and transforming Karaj to an industrial and commercial city are key roles in city’s growth. Metropolises have profound impacts on hinterland and lead to major transformations of surrounding area due to increased population and mutual spatial impacts and functional relationships. Until 1966, the City of Karaj had an image like garden city. However, todays this city is characterized by inappropriate neighborhoods, improper construction along Tehran and Qazvin highway, multiple scattered urban systems around the villages in the Karaj hinterland, connection of small towns to the city due to growth of immigration and the destruction of green space, transfer of fresh water to Tehran for citizens’ consumption, abandoned streams of Karaj River and intentional and unintentional drying of gardens.