Assessment of potential of physical development and expansion of Pardis new town, emphasis on geomorphological indexes

Extended Abstract
Introduction
Physical development and expansion of a city or town is dynamic and current process in which physical and legal boundary or limit of the city and physical spaces increase in both directions: vertical and horizontal in point of view of quantities and qualities. One of the main characteristics of urbanization process in Iran is fast expansion of cities and towns. As a Result of new changes, cities are changing very fast. These changes in form of population growth and physical expansion have been uneven and without any adherence. New town of Pardis has 30 kilometers away from east of Tehran, capital of Iran and in the direction of Tehran – AbAli. This city has planned and designed for settling about 150,000 people from Tehran population because of many advantages. It has limited from west to Jajrood river, from north to Alborz mountain ranges, from east to town of Boomhen and form south to some villages like Keresht, Siahsang, TaherAbad and plain of Varamin. The town of Pradis has the form rectangular. The role of Pardis new town is very important that it can beckon added population from Tehran Metropolis. For this reason, it would have a large increment in population growth and finally urban growth and sprawl. This issue that expansion and physical development of this town could direct where and how, is one of the most important issues and challenges. Locating Pardis in a mountain zone that could emerged many severe problems especially geomorphologic problems would be a serious challenge in future. Morphological indexes such as altitude, slope, distance from faults, distances from rivers, land use, land cover and so on can act as limitation in urban expansion of Pradis.
Methods
For doing this research, in addition to use documentary ways for gathering necessary data and information about studied area, it has used from topographical maps, Tehran map and geological map of Tehran province in software of Arc GIS. Then, according to the subject, seven criteria in which can make limitation on physical growth of town has studied. Studied criteria respectively are altitude, slope, distance from faults, land use, distance from river, and erosion. Using AHP model, final map of potential sites for physical development has drew and produced in three classes of good, medium and poor.
Findings and Results                           
Based on the maps that have produced about selected indicators, from the point of view of index of slope, most parts of Pardis town are located in the class of less favored and very less favored. In point of view of altitude, many parts of the town are in border of less favored and some parts are in border of medium. It is because this town is located in a mountainous site that all around the town are high mountains where it is not favor for urban structures. In point of view of geological and lithological indicators, many parts of the studied town are located in less resistant, about distance from basin buffer, almost all parts of the town is located in the class of high favored, about land use, many parts of the town in the class of medium, about soil erosion, all parts of the town are located in lands with high ability of erosion and finally about distance from faults about two third of the city built up area is located in very favored class, but some parts in the south there are some very high risk faults.
Conclusion
Generally, based on the seven factors which show geomorphological possibilities and limitation, it can concluded that the site of Prdis new town is a very less favored place and as the final map reveals this town also has many limitation in point of view of geomorphological indicators for the next expansion and growth. The last map also shows that there are some parts of the peripheral lands which are favored for the next expansion of this town, just in northeast and southwest. Finally, we can conclude that site selection of new towns is a very important subject in urban and design plan and we have to pay attention to not only the current site and location of them, but also to their future growth and expansion.