Şehirlerin optimum nüfus büyüklüklerinin belirlenmesine yönelik yeni bir metod: Şehir-kitle indeksi
A new method to determining the optimum population capacity of cities:City-mass index
Yazar: MURAT ÖZDEMİR
Danışman: PROF. DR. HATİCE AYATAÇ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Şehir ve Bölge Planlama Ana Bilim Dalı / Şehir ve Bölge Planlama Bilim Dalı
Derece: Doktora, 2023
Konu: Şehircilik ve Bölge Planlama = Urban and Regional Planning
Dizin: Bölgesel planlama = Regional planning ; Kapasite planlama = Capacity planning ; Kent planlama = Urban planning ; Kentsel planlama =   ; Kırsal planlama = Rural planning ; Mekan planlaması = Space planning ; Merkezi planlama = Central planning

Özet:
Yaşam alanlarımızı oluşturan şehirlerimiz gerek kendi doğal nüfus artışlarıyla gerekse kırsaldan aldıkları göçlerle büyümekte ve gün geçtikçe daha yoğun hale gelmektedirler. Şehirde üretilen ekonomi üzerinden yapılan planlama yaklaşımları da bu eğilimi arttırıcı yönde sonuçlar doğurmaktadır. Ancak artan şehirleşme, fırsatlarla birlikte bazı problemleri de beraberinde getirmektedir. Hava ve su gibi çevresel kaynakların kirlenmesi, güvenlik problemleri, yaşam maliyetinin yükselmesi, stres ve trafik gibi sorunlar ortaya çıkmaktadır. Şehirleşmenin yaygınlaşması ve şehirsel büyüme ile oluşan temel problemlerden bir tanesi de, ülke nüfusunun şehirlerdeki dengesiz dağılımı ve bunun sonucu olarak da ülkede bölgeler ve şehirler arası yatırım/büyüme/gelişme/kalkınma farklılıklarının oluşmasıdır. Oluşan bu farklılıklar belli bölgelerde şehirleşme eğilimini arttırmakta, bu da dengeyi git gide daha da bozmaktadır. Günün sonunda da, hakça paylaşılması ve genel refahı arttırması beklenen ülke kaynakları belli bir bölgede kullanılır olmaktadır. Oysa bu kaynakların ülkenin geneli için dengeli bir şekilde kullanılabilmesinin sağlanması, sürdürülebilir kalkınma ve toplum huzuru için önemlidir. 
Bu çalışma ile mevcut literatürde çoğunlukla sosyoekonomik dinamikler üzerinden ele alınan şehirsel büyümenin, yerleşim yerlerinin gerçekteki doğal ve fiziki şartları ile ilişkisinin nasıl kurulması gerektiği ana sorusuna temellenerek uygulanabilir yeni bir yöntem önerisi yapılmıştır. Bu yöntem ile ülke nüfusunun, şehirlerin kendi dinamikleri ile belli yerlerde yoğunlaşması yerine, dengeli dağılımının teorik altyapısını oluşturmak, şehirlerin olması gereken nüfuslarını müstakil olarak değil ama genel ülke sistemi içerisinde değerlendirerek şehir-kitle indeksi ve "obe-city" skalasını literatüre kazandırmak amaçlanmıştır.
Genel olarak şehirlerin oluşumları ve gelişimleriyle ilgilenen coğrafya, ekonomi, siyaset ve şehir planlama disiplinleri, ilgilendikleri şehri müstakilen değerlendirerek, şehri maksimum kapasite kullanımı ile maksimum fayda üretme üzerine kurgulamaktadırlar. Oysa şehirler müstakil mekânlar olmayıp, ülkenin dengeli gelişmesi ve kalkınması adına ülke bütünlüğü içerisinde diğer şehirlerle birlikte bir sistemi oluşturmaktadırlar. Şehirlerin fonksiyonları ve büyüklükleri de bu sistem içerisinde belirlenmelidir. Bir mekânda var olan şehirlerin fonksiyonlarını ve kapasitelerini öncelikli olarak belirleyecek ve sınırlayacak olan bu mekânın özellikleridir. Bu nedenle her yerleşim yerinin coğrafi özellik ve doğal şartlarından yola çıkılarak ve sistemi oluşturan diğer yerleşim yerleri ile birlikte etkileşimi modellenerek yerleşim yerlerinin alması gereken nüfusun tespit edilmesine çalışılmıştır. 

Bu doğrultuda, yerleşim yerlerinin nüfus alma kapasitelerinin belirlenmesinde; "Yerleşim yeri alanı, Topoğrafik koşullar, İklim özellikleri, Su kaynakları potansiyeli, yerleşim yeri Ekonomik Faaliyet potansiyeli, Afet riski, Ulaşım ve Erişilebilirlik olanakları" dikkate alınmıştır. Bu özelliklerin yerleşim yeri seçimindeki ağırlıkları, yapılan uzman anketi ile belirlenmiştir. Türkiye örneğinde 81 il, bu özelliklerine bağlı puanlanmış, ağırlık katsayıları ile çarpılıp, toplanıp, oranlayarak illerin nüfus alma kapasiteleri (rijitlikleri) hesaplanmıştır. Hesaplanan bu rijitlikleri üzerinden ülke nüfusundan almaları gereken nüfus miktarı hesaplanmış, hesaplanan bu nüfus miktarları ile halihazırdaki nüfus miktarları karşılaştırılarak şehirlerin nüfus yükleri belirlenmiştir. Bu belirlenen nüfus yüklerine göre iller, geliştirilen şehir-kitle endeksine göre; "Seyrek Yoğunluklu", "Düşük Yoğunluklu", "Dengeli Yoğunluklu", Yoğun" ve "Aşırı Yoğun (obe-city)" olarak sınıflandırılmışlardır.
Bir ülke için esas olanın, şehirler ve bölgeler arası gelişmişlik ve yoğunluk farklarını çok olmaması, dengeli olmasıdır. İllerin hesaplanan nüfus alma kapasiteleri ile nüfus yükleri birlikte değerlendirilerek, nüfus alma kapasitesi yüksek olmasına rağmen bu kapasitesini kullanamayan iller ile kapasitesinin üzerinde nüfusu olan iller tespit edilmiştir. Nüfus yükü az olan illerde yerleşilebilir alan üreterek, nüfus yükü fazla olan illerden buralara nüfus hareketini planlamak ve teşvik etmek ülke genelinde nüfus ve kalkınmanın daha dengeli olmasını sağlayacaktır.
Seçilen yerleşilebilir alan kabullerine göre Türkiye illerinin yaklaşık %70'i Seyrek ve Düşük Yoğunluklu, %22'si Dengeli Yoğunlukta ve Yoğun çıkmıştır. Bir kabule göre 6, diğer kabule göre de 4 ilimiz Aşırı Yoğun (obe-city) çıkmıştır.  
Bu çalışma ile bu dengenin ne yönde bozulduğunun tespiti ve hangi şehirlerde nüfusu ve istihdamı arttırıcı politikaların geliştirmesi gerekeceği, hangi şehirlerde yatırımlara öncelik verileceği konularında yön gösterici olunması amaçlanmıştır. Özellikle bölgesel stratejik mekânsal planlama kararlarının alınmasında bu tespitler altlık olarak kullanılabilir. Bu kapsamda öncelikle kapasitesini kullanamamış olan illerin kapasitelerini kullanma ve arttırmalarına yönelik ekonomik, sosyo-kültürel, altyapı ve üst yapı yatırımları planlanmalıdır. Geliştirilen bu metod, farklı kriterler ile farklı şekilde modellenebilir, özelleştirilebilir ve genişletilebilir niteliktedir.

Abstract:
The cities that comprise our living areas are getting denser by the day. The natural population growth of the cities and migration from the rural are the main causes of this density. Planning approaches based on the economy produced in the city also increase this trend. However, increasing urbanization brings some problems along with opportunities. Problems such as pollution of environmental resources such as air and water, safety problems, increased cost of living, stress and traffic arise. One of the main problems that occur with the spread of urbanization and urban growth is the uneven distribution of the country's population in the cities and the consequent formation of investment/growth/development differences between regions and cities in the country. These differences increase the tendency of urbanization in certain regions, which further destabilizes the balance. At the end of the day, the resources of the country, which are expected to be shared fairly and increase the general welfare, are used in a certain region. However, the balanced use of these resources for the country as a whole is important for sustainable development and social peace. 
The aim of this study is to find the current population loads of cities by calculating the balanced distribution of a country's population on the basis of the physical and natural environments of the cities.
This study consists of five main chapters. The first chapter introduces the subject and includes the purpose, scope and method of the study.
In the second chapter, the approaches in the literature on urbanization and the growth of cities and the theoretical basis of our approach to the subject within the scope of this study are discussed.
The third chapter provides an explanation, compilation, and evaluation of our study's methodology as well as the data that were employed.
Following the presentation of the study's results in the fourth chapter, the fifth chapter evaluates these results.
It can be seen in the literature that there are two basic approaches regarding urbanization and population sizes of cities. Both approaches basically consider urbanization and urban growth as an inevitable phenomenon of our age. The first approach, while not ignoring the problems brought by urbanization, defends the natural flow of the urbanization dynamic through a free market economy in line with neo-liberal policies. According to the other approach, urban sprawl resulting from urban growth will create extra infrastructure and superstructure costs for local governments. For this reason, the growth of cities should be controlled with special policies to be implemented in order to eliminate the problems caused by intense urbanization and to maximize social benefit. 
The main questions of this study are "Should cities be able to grow as much as they can?" and "Shouldn't cities have a population limit, just like living organisms have a weight limit?". It was based on the argument that urban growth and population growth should be a balance point. In this context, three basic hypotheses were put forward in the study.
The life cycles and urban functions of cities are very similar to the vital cycles and functions of living organisms. In other words, just as observed in living organisms, cities grow and develop, their population increases, settlement areas expand, they have diseases like humans, they can be exposed to disasters, famines, wars, and they can die, collapse, or disappear like humans. Life cycles, which can only be expressed in 10 years for humans, can be expressed in 100 years for cities. Cities, just like living organisms, have a limited life cycle, and just as excessive weight in living organisms negatively affects the quality and lifespan of living organisms, an excessively increasing population despite limited resources also negatively affects the quality and cycle of life in cities.
According to this background, our first hypothesi is, "Ideal body sizes and weights, which are important for people's health and quality of life, are also important for the healthy development of cities, and in this context, ideal population sizes should be defined for cities."
In the body-mass index, which is used to determine people's ideal body size, a correlation has been established with people's height and weight, that is, only two physical characteristics. Since cities are ultimately established in places, the parameters that will determine the size, settlement capacity and population of cities should primarily be the natural and physical characteristics of this place. So our second hypothesis is, "Settlements present the potential for growth and population carrying capacity according to their physical and natural characteristics."
In the current literature, the developments, growth and population increases of cities are mostly evaluated and interpreted within their own socio-economic dynamics and opportunities. Some cities, which have become centers of attraction both regionally and throughout the country, attract more population than other cities. This situation necessitated more investments in those cities. As a result of the social and economic opportunities created by the excessive investments made, these cities continue to attract more population. As a result, the country's population is not evenly distributed among the cities of the country. However, cities are not independent structures, independent from other cities of the country. They form the country's ecosystem together with other settlements within the integrity of the country for the sake of general income distribution and balanced development of the country. Therefore, they have to share the population load of the country in a balanced manner. So, our third hypothesis is; "The population sizes of cities should be determined in interaction with other cities of the country, considering their natural and physical conditions."
The general lines and stages of the developed method are structured as follows;
1-	Determination of the study area and the individual settlements within this area, (In our study, our study area was determined as the whole of Türkiye and the individual settlements were determined as 81 provinces.)
2-	Determining the evaluation criteria of the settlements to be evaluated,
Since cities are built in space, the physical and natural conditions of the this space appear as a determining factor in urbanization and the population size of the city. The most important of these physical conditions is the area of the settlement. Naturally, it can be predicted that the larger the area of a settlement, the more population it can accommodate. However, not all of the area designated for a settlement is suitable for settlement. Forest, agriculture, pasture, wetland, mine, protected area etc. areas like these are not areas of settlement. Therefore, the size of the habitable area should be taken into consideration when evaluating the size of the settlement. Two alternatives were considered in determining the habitable areas of cities. In the first alternative (A1), areas "Land Principally Occupied by Agriculture, With Significant Areas of Natural Vegetation" are added to the "Artificial Areas" according to the Corine Land Cover definition. In the second alternative (A2), in addition to the areas in A1, "Non-irrigated Mixed Farm areas" and "Irrigated Mixed Farm Areas" were added.
According to our approach, "The natural/physical characteristics of the settlement area, will determine the settlement capacity of cities", settlement suitability and attractiveness/rigidity coefficients were calculated according to the natural/physical environmental characteristics of the cities. In the calculation of these coefficients, the net habitable area of the settlement, topographic conditions, climate characteristics, water resources, economic activity potential, disaster risk and transportation and accessibility were taken into account. Social, demographic, economic, political and historical factors and socio-economic data are excluded from the research framework.
The factors and subfactors that will be subject to evaluation in determining the population capacity (rigidity) of the settlements according to their natural/physical environmental characteristics have been determined as follows. 
• In topographic conditions; The altitude of the settlement, whether it is established on a plain, hillside, plateau, valley or waterfront,
• In climate features; having an arid, temperate or rainy climate,
• In water resources; water poverty, water scarcity and water richness situation,
• In economic activity potential; the region's predisposition to agriculture, industry or service sectors,
• At disaster risk; The degree to which the region is at risk of disaster,
• In terms of transportation and accessibility, the region's land, sea, air and rail transportation facilities were evaluated.
3-	Determining the weight coefficients of the evaluation factors,
First of all, the weight coefficients of the impact of the above data main factors and data subfactors on settlement selection were determined. The Expert Opinion method was used to determine these coefficients, and for this purpose, the "Expert Questionnaries" prepared via Google Forms was distributed to the branches of the Chamber of Urban Planners and to all City and Regional Planning Departments and Faculty Members of Geography Departments of universities. Weight coefficients were determined according to the results of the survey completed with 111 participants. According to the results of the expert survey, the weight coefficients of the main factors are as follow: economic activity potential (20.3%), transportation and accessibility (18.33%), climate features (16.32%), water resources (16.32%) (15.83%), topograpic conditions (15.28%) and disaster risk (13.95%).
4-	Scoring of the settlements, here provinces of Türkiye, to be evaluated according to the determined criteria,
Afterwards, the situations of the provinces under the relevant data subfactors were scored by using sources such as TUIK, official data of the relevant Ministries or General Directorates, geographical information and literature.
5-	Calculating the stiffness values of the provinces by multiplying the scores of the provinces with the relevant factors' weight coefficients, adding them up and proportioning them,
6-	Distribution of the data whose distribution is sought (in our study, this data is population) according to the stiffness values of the provinces,
Based on our approach that cities are not independent structures but are within the country's ecosystem, it is envisaged that cities will share the country's population according to their suitability for settlement and population carrying capacity, calculated according to their natural/physical environmental characteristics. In this context, the population of the country is distributed among the provinces according to the calculated stiffness of the provinces, similar to the principle in Civil Engineering,  that the load-bearing elements shares the horizontal loads acting on the structures  according to their stiffness.
7-	Comparison of the calculated population data of the provinces at the end of this distribution with the current population data,
8-	Creating a "city/mass index" by calculating the population load based on the "current population" / "calculated population" ratio.
According to these calculated population loads and developed city-mass index, cities are classified as follow: Population Load:PL=0,00-0,75 "Low-Loaded", PL=0,75-1,00 "Under-Loaded", PL=1,00-1,25 "Balanced", PL=1,25-2,50 "Loaded" and PL>2,50 "Over-Loaded (obe-city)". 
What is essential for a country is that there are not many differences in development and density between cities and regions, and that it is balanced. By evaluating the calculated population attraction capacities of the provinces and their population loads together, the provinces that had a high population capacity but could not use this capacity and the provinces with a population above their capacity were identified. Planning and encouraging population movement from "Loaded" and "Over-Loaded" provinces to the "Low-Loaded" and "Under-Loaded" provinces by producing new settlement areas, will ensure that population and development are more balanced throughout the country.
According to the selected settlement area assumptions, approximately 70% of Turkey's provinces "Low Loaded" and "Under Loaded", 22% are "Balanced" and "Loaded". According to one alternative, 6 provinces and according to the other alternative 4 provinces are considered "Over-Loaded" (obe-city).
With this study, it is aimed to determine the direction in which this balance is deteriorated, to be a guide in which cities will develop policies to increase population and employment, and in which cities to give priority to investments. 
The findings can provide a baseline for the development of investment policies to influence the population distribution in the Turkish provinces. The reason is that the populations of the provinces with obe-cities and overcrowded cities should be reduced, and those of the provinces with balanced cities should be preserved. The remaining provinces should be revitalised on the basis of their population levels and socioeconomic development patterns. 
In order to reduce the density in "Loaded" and "Over-loaded" provinces and enable the population to settle in other provinces, investments will first need to be made to increase the attraction power of those "Low Loaded" and "Under Loaded" provinces. With this model, it will be possible to calculate which of these provinces there will be and whether there will be a population movement from which provinces to which provinces, taking into account regional characteristics. In this way, the country's population will be distributed more evenly throughout the country, which will contribute to development in a more balanced manner throughout the country.
In addition, it will enable the identification of provinces with high population loads, "Loaded" and "Over-loaded" provinces with high disaster risk, that is, with low disaster scores, and work to be carried out in these provinces to both reduce the population load and make the building stock resilient. In this context, the provinces with high disaster risk and high population load are Istanbul, Izmir, Düzce, Yalova, Hatay, Hakkari, Sakarya, Kocaeli, Bursa, Şırnak, Iğdır. Among these provinces, there are provinces affected by the 1999 Gölcük and Düzce and the 6 February 2023 Kahramanmaraş earthquakes. According to these outputs, it should be expected that priority will be given to efforts to make physical spaces in these provinces more resistant to disasters.
Basically these findings can be used as a baseline, especially in making regional strategic spatial planning decisions. In this context, first of all, economic, socio-cultural, infrastructure and superstructure investments should be planned for the provinces that have not been able to use their capacities to use and increase their capacities. This developed model can be modeled, customized, expanded and improved with different criterias for different cases.The methodological framework also can be generalised, assessed, and improved; thus, it can be applied to provinces in other countries.