عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The population of the world during the last few decades has had rapid and drastical growth. It has been documented that during 1950 to 1990 the urban population has increased three times i.e. from 730 million up to 2.3 billion. It is expected that this rapid growth become double until 2020 out of which 93% will be related to urban population of the developing countries. Thus it is essential that the required programs and planning should be considered for the upcoming over load of urban population. Before the few recent decades, most of Iranian cities have a balanced growth rate; however, in recent decades, urbanization has been preferred to urbanism which is due to a set of attractive factors on the part of cities beside the detractive factors of the villages. This is in turn led city expansion to serious problems. The township of Marvdasht, in its 70 year lifespan, has followed a variety of processes and patterns of physical growth, and has developed in an unbalanced order.
Marvdasht city with its natural, industrial, economic, and tourism attractions has been recognized as one of the major pole of population and has had a remarkable growth of physical extension over the recent years. This undesirable growth has been due to the existing population as well as the migrated people to the city which has led to unplanned and poor physical construction of the city and has covered the agricultural land in a large scale. The population evolution of Marvdasht city during the current years is the result of turbulence which is affected by economical and social conditions of the region. The population of the city over the last 50 years 5.4% has grown and its population has increased from 8987 to 124350. From structural point of view the city has been formed in an integrative way out of which most of the areas have been located within the legal part of the city.
The total areas of the city have been reported 1712 hectares out of which 60% is recognized as normal condition while the other part constitutes the sprawl extension. In fact, this city has had regular population growth and normal physical extension till 1996, but since then due to lack of proper urban planning and policy making there hasn’t been a parallel growth between physical extension and the increasment of population as a result the physical expansion has been more than the population growth and the city has rapidly expanded. The present pattern of physical expansion of Marvdasht city is mixed and has been affected by linear and checkered forms. This condition caused the city to develop along the axis road of Shiraz –Isfahan and its peripheral streets extend in the form of checkered to other parts of the city. On the other hand, during the recent years, the city authorities to reduce the traffic jam and prevent the linear expansion of city have constructed streets suitable direction of major network of western and eastern parts of the city. Although, this policy has played a role in proper checkered formation with extended structure of the city, the special structure of Marvdasht has been formed in a way that the total axis of industrial, transportation, warehouse holding, agricultural and residential areas have been located in the same neighborhood and this situation invokes a specific spacial- location relationship.
The present research is done by comparative-analysis study method, by the help of Shannon’s and Heldren entropy models, to analyze how this township has developed. The results indicate that the township has developed in a concentrated manner up to the year 1997; however, after this time, it developed in an urban sprawl (spiral) way, which latter cases amount is specified using these 2 models. The results analyzed by Heldren model shows that during the1966 to 2008 over 67% of the physical extension of the city related to the population growth and the remaining 33% is related to vertical and sprawl growth of city and its affect has been on the reduction of impure density of the population and incensement of impurity of land percapita of city.
Although, according to the current growth pattern of the township which is more of a linear form, and secondly, the increase in the entropy value gap due to the horizontal and spiral growth of the city; the latter in turn influenced by the linear growth pattern, now (2008), the best future pattern was determined as centralized sectorial method for the township. For this to take effect, we should use the intra-textual concentration expansion pattern, and simultaneously, contiguous sectorial pattern along with the system of crossover and diagonal communicative network. If so, we will see a reverse inclination towards urbanism prior to urbanization in the next stage, in order to optimize the future development perspectives, a setting of GIS soft ware’s and related models were employed. Last after the indication of index and layers and merging and intercovering of layer, proper town development site were extracted. It is worth mentioning that for the sake of easy and comfortable connection. In the transportation network of the city, along with intersecting network there must be established across network.