Morphological Analysis of Population Distribution in Tehran Metropolitan Region (TMR)

Document Type : Research Paper

Authors

1 Associate professor of urban and regional planning, Faculty of Arts and Architecture, Tarbiat Modares University, Tehran, Iran

2 MA in regional planning, Tarbiat Modares University, Tehran, Iran

Abstract

Introduction
“Form follows function”; a controversial statement that in last two decades has gained more attention especially in spatial planning context; how are forms the reflection of functions and vice versa. Spatial structure of regions has to be a means of spatial planning to understand the dynamics of population and employment through space and time. Methodologically, it consists of two main approaches, functional and morphological, in investigation of relational and nodal features of centers, respectively. Population spatial structure in metropolitan regions represents settlements configuration and mobility while employment structure investigates the dynamics of money, labor, goods, and information in the region. Generally speaking, the spatial structure of regions has a variety of elements. However, CBD, employment sub-centers, and infrastructures are the most influential parts affecting the location and mobility of population and its employment.
The subject of the spatial structure of metropolitan regions are over studied and a long history and rich literature are formed in local, regional, national, and even international levels. However, as this concept is highly context dependent, in various geographies may have different meanings and mechanisms. This study has investigated the issue in the Iranian context. The spatial structure of metropolitan regions may have different patterns, while monocentricity and polycentricity are the most common phenomena that can explain the whole situation. Metropolitan region spatial structure is a fuzzy concept from mono-centric to completely polycentric. In the literature, this structure is mainly affected by triple factors; CBD, subcenters, and transportation infrastructures. As spatial planning is an interdisciplinary subject, most theories and methodologies are taken from different fields, so most of the models used in this paper are economically based subjects combined with spatial aspects.
The aim of this study is to analyze the distribution of the population in Tehran Metropolitan Region (TMR) by a morphological approach. Thus, three main questions can be addressed; what is the relationship between population distribution and distance to CBD? How much population density in TMR is affected by transportation network? And, what are TMR sub-centers and is there any relation between them and population density? 
Methodology
The morphological approach is applied in this study that refers to the plurality of centers in a given territory. As the main objective is to assess the influence of some factors on population distribution, we used various types of regression functions. Required data for the proposed methods are acquired from the Statistical Center of Iran (SCI) and corrected by the authors. To evaluate the relationship between CBD and population density, different forms of monocentric functions adopted that the most useful and commonly used forms are linear, gravitational, exponential and logarithmic. In terms of transportation networks (highway and freeways), several forms of univariate regression functions are used to assess the relationship between population density and distance to the nearest network. The third part of this study is evaluation of the influence of subcenters on population density that is more challengeable because of the majority of the methods proposed in subcenters identification; most of them have a kind of arbitrary state. However, we used a combination of adopted models including threshold method, density and proportional based method, parametric model, GWR, and ESDA. Then, in a multivariate nonlinear function, we investigated relation between population density and distance to nearest subcenters. In the end, a linear integrated model is used to assess the population density changes based on distance to CBD, transportation network and subcenters simultaneously. In all cases used OLS technique is applied to estimate variables.
 
Results and discussion
Tehran Metropolitan Region (TMR) is the most important and populated region in Iran. TMR almost encompass all Tehran Province, but by the parliamentary approval (2010), it divided into two separate provinces, Tehran and Alborz. Tehran City is considered as the center the Tehran province and Karaj is the center of Alborz. Tehran city has been the capital of Iran from 1776 up to now and the population is increased from 15000 to 8154051 inhabitants in 2011. In this period, Tehran has become a great metropolitan region by 18000 square kilometers area and a population of 14 million, according to the last census (2011). TMR includes 14 counties (Shahrestan), 54 cities and 87 rural districts (Dehestan), in total 141 administrative sections. Population decentralization was started in 1976-86, that is mainly due to Islamic Revolution in the 1979. It should be noted that the increased rate of population doesn’t mean the decentralization of population from Tehran city, even though these inhabitants are attracted from other parts of the country.
The results of a monocentric model to assess the relationship between population density and CBD is not significant (R2=0.1). This means that CBD cannot explain the population density variation. However, OLS results of road-based models show no considerable significant relationship but it is more powerful than CBD variable. A large number of subcenters identification methods are applied in TMR to find appropriate and applicable methods. The results found six subcenters including Karaj, Eslamshahr, Baghershahr, Nasimshahr, Varamin, and Rey. In the next step, OLS results of regression model demonstrated a high value of GOF (goodness of fit (R2=0.5)) that confirmed the hypothesis of the research about slight polycentricity of TMR population distribution. Finally, the results of the integrated model to test the comparative importance of triple variables (CBD, subcenter and transportation network) on population density, surprisingly demonstrated that road is the most important factor, subcenter and CBD are in the lower level of significance, by -5.65, -1.18 and 0.45 t-value, respectively.
 
Conclusion
This research aimed to describe and analyze the population spatial structure of TMR. The results showed the effects of transportation networks, subcenters, and CBD on population distribution over TMR territory by different levels of significance. Therefore, the empirical evidence obtained from TMR allows us to state that the monocentric model cannot explain the dynamics of TMR population distribution. Although it does not mean that TMR is significantly polycentric, a degree of polycentricity could be considered in this case. 

Keywords

Main Subjects


  1.  آراسته مجتبی، داداش‌پور، هاشم و علی‌اکبر تقوایی، 1395، ارائة چهارچوب نظری مناسب ساختار فضایی بندرها و مناطق پسکرانه‌ای بر مبنای روش تحلیل محتوا، مدیریت شهری، شمارة 44، صص 19-40.
  2. داداش‌پور، هاشم، 1390، تحلیلی بر عوامل تعیین‌کنندة مزیت‌های مکانی در منطقة کلان‌شهری تهران: شواهد تجربی از چهار بخش صنعتی، فصلنامة آمایش محیط، دورة چهارم، شمارة 16، صص 91- 116.
  3. داداش‌پور، هاشم و آتوسا آفاق‌پور، 1393، ساختار و سازمان فضایی در نظام شهری ایران با استفاده از تحلیل جریان هوایی افراد، فصلنامة پژوهش‌های جغرافیای انسانی، دورة 46، شمارة 1، ص 125.
  4. داداش‌پور، هاشم و امیررضا لواسانی، 1394، تحلیل الگوهای فضایی پراکنده‌رویی در منطقة کلان‌شهری تهران، فصلنامة برنامه‌ریزی فضایی، سال پنجم، شمارة اول، صص 123-146.
  5. داداش‌پور، هاشم و سپیده، تدین، 1394، تحلیل نقش الگوهای سفر در ساختاریابی فضایی مناطق کلان‌شهری: مورد مطالعاتی منطقة کلان‌شهری تهران، فصلنامة آمایش جغرافیایی فضا، سال پنجم، شمارة 18، صص 65-86.
  6. ــــــــــــــــــــــــــــــــ، 1394، شناسایی پهنه‌های همگن جریانی براساس جابه‌جایی‌های فضایی و الگوهای سفر: مطالعة موردی منطقة کلان‌شهری تهران، مطالعات شهری، دورة 4، شمارة 14، صص 61- 76.
  7. زبردست، اسفندیار و خلیل حاجی‌پور، 1387، تبیین فرایند شکل‌گیری، تکوین و دگرگونی مناطق کلان‌شهری، پژوهش‌های جغرافیای انسانی، شمارة 69، صص 105-121.
  8. مرکز آمار ایران، سرشماری نفوس و مسکن سال‌های 1385 و 1390، نتایج تفصیلی استان‌ها، استان‌های تهران و البرز.

 

  1. Alonso, W., 1964, Location and land use, Toward a general theory of land rent, Cambridge: Harvard University Press.
  2. Anas, A., Arnott, Richard and Kenneth A Small, 1998, Urban spatial structure, Journal of economic literature:1426-1464.
  3. Anselin, L., 1995, Local indicators of spatial association—LISA, Geographical analysis Vol. 27, No. 2, pp. 93-115.
  4. Batty, M., 2009, Urban modeling, International Encyclopedia of Human Geography, Oxford, UK: Elsevier.
  5. Baum-Snow, Nathaniel, 2007 a, Did highways cause suburbanization?  The Quarterly Journal of Economics, Vol. 122, No. 2, pp. 775-805.
  6. __________________, 2007 b, Suburbanization and transportation in the monocentric model, Journal of Urban Economics, Vol. 62, No. 3, pp. 405-423. doi: http://dx.doi.org/10.1016/j.jue.2006.11.006.
  7. Bertaud, A., 2003, Tehran spatial structure: Constraints and opportunities for future development, Ministry of Housing and Urban Development, Tehran.
  8. ___________, 2004, The spatial organization of cities: deliberate outcome or unforeseen consequence?, Unpublished paper http://www.alain-bertaud.com/AB_Files/AB_Central%20European%20Spatial%20Structure_Figures_2.pdf.
  9. Burger, M., and Evert Meijers, 2012, Form follows function? Linking morphological and functional polycentricity, Urban Studies, Vol.49, No. 5, pp.1127-1149.
  10. Cladera, J,R., Carlos R Marmolejo Duarte and Montserrat Moix, 2009, Urban structure and polycentrism: towards a redefinition of the sub-centre concept, Urban Studies, Vol. 46 , No.13, pp. 2841-2868.
  11. Coffey, W,J. and Richard G Shearmur, 2002, Agglomeration and dispersion of high-order service employment in the Montreal metropolitan region, 1981-1996, Urban Studies, Vol. 39, No.3, pp .359-378.
  12. Dadashpoor, H., Afaghpoor, A., and Andrew A., 2015, A Methodology to Assess the Spatial Configuration of Urban Systems in Iran via interaction view, Geo-Journal, 10.1007/s10708-015-9671-1.
  13. Davoudi, S., and Strange I., 2008, Concepts of space and place in spatial planningRoutledge.
  14. ___________ 2003, Polycentricity in European spatial planning: from an analytical toolto a normative agenda, European Planning Studies, Vol. 11, No. 8, pp. 979-999.
  15. Fujita, M., and Hideaki Ogawa, 1982, Multiple equilibria and structuraltransition of non-monocentric urban configurations, Regional science and urban economics, Vol.12, No. 2, pp.161-196.
  16. Fujita, M., and et al, 2013, The von Thünen Model and Land Rent Formation Economics of Agglomeration: Cambridge University Press.
  17. Garcia, López, M., and Muñiz, I., 2010, Population suburbanization in Barcelona, 1991–2005: Is its spatialstructure changing? Journal of Housing Economics, No. 19, pp. 119–132.
  18. Garcia, López, and et al,. 2015, Suburbanization and highways in Spain when the Romans and the Bourbons still shape its cities, Journal of Urban Economics, Vol. 85, pp. 52-67. doi: http://dx.doi.org/10.1016/j.jue.2014.11.002.
  19. Garcia, L., Miquel, À., and Ivan Muñiz, 2010, Employment decentralisation: polycentricity or scatteration? The case of Barcelona, Urban Studies.
  20. Garcia, L., Miquel, À., 2012, Urban spatial structure, suburbanization and transportation in Barcelona, Journal of Urban Economics, Vol. 72, No. 2, pp.176-190.
  21. Giuliano, G., and Kenneth A Small, 1991, Subcenters in the Los Angeles region, Regional science and urban economics, Vol. 21, No. 2, pp.163-182.
  22. Giuliano, G. , and et al, 2007, Employment concentrations in Los Angeles, 1980–2000, Environment and Planning A, Vol. 39, No. 12, pp. 2935-2957.
  23. Hall, P.G, and Kathy P, 2006, The polycentric metropolis: learning frommega-city regions in Europe: Routledge.
  24. Healey, P., 2004, The treatment of space and place in the new strategic spatial planning in Europe, International journal of urban and regional research,Vol. 28, No.1, pp. 45-67.
  25. Kim, J.k, Chang H.Y, and Jin, H.K, 2014, Spatial change in urban employment distribution in Seoul metropolitan city: clustering, dispersion and general dispersion, International Journal of Urban Sciences, Vol. 18, No. 3, pp. 355-372.
  26. Mc, D., John F., and Daniel P. M, 1990, Employment subcenters and land values in a polycentric urban area: the case of Chicago, Environment and Planning A, Vol. 22,  No. 12, pp.1561-1574.
  27. Mc,D., John F, and Paul J.P, 1994, Suburban employment centres: the case of Chicago, Urban Studies,Vol. 31, No. 2, pp. 201-218.
  28. Mc, M, Daniel P, and William Lester T, 2003, Evolving subcenters: employment and population densities in Chicago, 1970–2020, Journal of Housing Economics, Vol.12, No. 1, pp. 60-81.
  29. Muñiz, I., and et al., 2008, The effect of employment sub-centres on populationdensity in barcelona, Urban Studies, Vol. 45, No. 3, pp. 627-649.
  30. Park, R.E, Ernest W. B, and Roderick D.M, 1984, The city, University of Chicago Press.
  31. Parr, J.B, 2014, The Regional Economy, Spatial Structure and Regional Urban Systems, Regional Studies, Vol.48, No.12, pp. 1926-1938.
  32. Riguelle, F., Isabelle T., and A., Verhetsel, 2007, Measuring urban polycentrism: a European case study and its implications, Journal of Economic Geography.
  33. Sun, T., and et al, 2012, Suburbanization and subcentering of population in Beijing metropolitan area: Anonparametric analysis, Chinese Geographical Science, Vol. 22, No. 4, pp. 472-482.
  34. Vasanen, A., 2012, Functional polycentricity: examining metropolitan spatial structure through the connectivity of urban sub-centres, Urban Studies, Vol. 49, No. 16, pp. 3627-3644.
  35. Veneri, P., 2013a, The identification of sub-centres in two Italian metropolitan areas: A functional approach, Citie, No. 31, pp.177-185.