عنوان مقاله [English]
In the years before industrial revolution in Europe, cities had mono-centric characteristic. After industrial revolution, cities changed and transformed from mono-centric configuration into poly-centric structure. At this moment theoretical concerns about cities had emerged. During 1920s and 1950s various theories came into the scene, describing cities as static entities. In 1960s and 1970s som cities in northern America gradually experienced a different growth and new dynamic states. After that in 1980s and 1990s, by appearing the new form of physical growth of cities, new problems and challenges had come into existence. Urban sprawl is one of the most important problems nowadays in metropolitan areas. It seems that the core of urban planning is land-use. There are lots of strategies and solutions for this problem. One of the solutions is ecological land-use strategy. There are also lots of descriptive and prescriptive models in this field, intelligent models such as CA, ANN etc.
Mashhad Metropolitan area with more than 3000000 populations is in terms of extent the second metropolitan area in Iran. This area because of its significant border situation plays an important role in national development of the whole country. This significant role is why it should be considered as the pole of national-regional development. The area has solely more than 75 percent of the population of Mashhad as well as about 90 percent of the added value of that region. The explanatory indices used in this area indicate an intensified imbalance and centralization of capital and power in the area. The logical consequence of this imbalance have led to urban sprawl and increasing accumulation of capital and power. This sprawl have had several consequences such as demolition of green and agriculture lands, land speculation, increasing environmental pollutions, ecological damages and mismatch of the developed land with the natural potentials of those lands. Thus, it is necessary to have an ecological criterion for judgment of the urban and rural settlements in the area.
This study is carried out in two parts. In the first part, an optimal land use pattern based on ecological principals will be formulated. In the second part, the output of the formulated results of the first part will be used as spatial criteria in order to simulate future land use changes based on the ecological output. To do so, a CA model will be associated with ANN algorithm. For this purpose, we’ll draw three different growth scenarios for 2026:
1. The objective of this part is initially by virtue of theoretical studies and fieldwork to identify appropriate ecological indices for urban and rural development; secondly an optimal land-use pattern will be produced by using AHP model based on each of aforementioned indices. Finally, by overlying all those patterns the final optimal land-use pattern will be generated.
2. In the second part, by using aerial photos of the years 1996 and 2011, we will identify the land use changes. In the next stage, the ecological layers produced in the first part will enter into the model and will be used as spatial variable. By using cellular automat and artificial neural network algorithm three growth scenarios will be simulated.
Brief explanation of the function of the model is as follow: (1) production of land use/ cover layers for the years 1996 and 2011; (2) use of ecological pattern as spatial variable and a direction for simulation for the two first scenarios in the one hand, and use of Euclidean distance from important settlements and major roads for the third scenario on the other hand; (3) creation of land use change matrix; (4) modeling of future changes potential; and (5) simulation of land use change for the year 2026 for each scenarios, i.e., radical ecological growth scenario, mild ecological growth and uncontrolled growth.
Results and Discussion
The results of the ecological pattern show that there are ten deciles. As we move from early deciles to tenth deciles we find more appropriate sites for development. The tenth decile is the existing settlements in the area. One of the results of this study is that the best and the ideal way of developing are infill development and maximum use of the existing developed lands. However, the first till fourth deciles are extremely bad sites for development. The fifth and sixth ones are not well enough but more appropriate compared with the former ones. The seventh and eighth are fairly appropriate.
In the second part, based on the ecological pattern and Euclidean distances of roads and settlements three scenarios will be simulated for 2026. In the first scenario, the amount of built areas is at the lowest, and is equal to 659 km2. In the second scenario, 735 km2 will be developed and according to this scenario parts of agriculture lands will be degraded. In the third scenario, 775 km2 will be developed which is in opposition to optimal ecological pattern.
The study draws three growth scenarios for 2026. The first one was a radical ecological growth based on the ninth and tenth deciles of the ecological pattern. The second one was a mild ecological growth based on the seventh till tenth deciles of the ecological pattern. Finally, the third scenario was an uncontrolled growth. The results show that the first scenario will retain the most portions of the green lands and is an endogenous growth. The second scenario is a mild one. Although it permits certain parts of green lands to be degraded, it is an acceptable model. In this scenario, some major nodes and some secondary ones will be presented. The third scenario (business as usual) is uncontrolled growth that will ruin lots of green lands. This can be concluded that continuation of the existing growth will lead to irreparable consequences in the area. Environmental crises such as water crisis, air pollution and pressure on infrastructure will lead to human crises like riots, crimes and vandalism. Thus, it is necessary that planning system consider reasonable growth.