Urban theories and models attempt to explain the internal morphology, growth patterns, and social zonation of cities. In settlement geography, these models are essential for understanding how land use (residential, commercial, and industrial) competes for space within an urban area.
Classic Concentric Zone Model (Ernest Burgess, 1923)
Based on the study of Chicago, Burgess proposed that a city grows outward from a central point in a series of five concentric rings.
- Zone I: Central Business District (CBD): The innermost zone containing retail, offices, and financial institutions. Land values here are the highest.
- Zone II: Zone of Transition: Surrounds the CBD. Characterized by deteriorating housing, small-scale light manufacturing, and high population turnover.
- Zone III: Zone of Independent Workingmen’s Homes: Occupied by stable families of blue-collar workers who moved out of the transition zone.
- Zone IV: Zone of Better Residences: Middle-class residential area with single-family dwellings and high-quality apartments.
- Zone V: Commuters’ Zone: The outermost ring consisting of suburban small towns and “dormitory” settlements.
Sector Model (Homer Hoyt, 1939)
Hoyt challenged the concentric ring theory, arguing that cities develop in wedge-shaped sectors radiating from the CBD along transport routes (railroads or highways).
- Transport Influence: High-rent residential sectors develop along specific axes (e.g., a scenic waterfront or high ground).
- Industrial Corridors: Low-income housing and industrial zones cluster along rail lines or river valleys.
- Filtering Process: As high-income groups move further out along a sector, their former houses are occupied by middle-income groups, creating a directional pull for growth.
Multiple Nuclei Model (Harris and Ullman, 1945)
This model posits that a city does not have a single focal point but multiple specialized centers (nuclei).
- Decentralization: As cities grow, functional activities like heavy industry, universities, or airports form their own clusters.
- Factors of Formation:
- Certain activities require specialized facilities (e.g., ports need waterfronts).
- Similar activities group together for “agglomeration economies” (e.g., financial districts).
- Incompatible activities stay apart (e.g., high-class housing avoids heavy industrial zones).
- Peripheral Growth: Includes the development of “Edge Cities” and industrial suburbs.
Central Place Theory (Walter Christaller, 1933)
While the previous models look inside the city, Christaller explains the spatial distribution of cities within a region.
- Hexagonal Hierarchy: To ensure that no area is unserved and to minimize overlap, settlements are arranged in a hexagonal pattern.
- Key Concepts:
- Range: The maximum distance people are willing to travel for a service (low for bread, high for jewelry).
- Threshold: The minimum population required to make a business or service viable.
- Principles (K-values):
- K = 3 (Marketing Principle)
- K = 4 (Transport Principle)
- K = 7 (Administrative Principle)
Comparison of Urban Growth Models
| Feature | Concentric Zone (Burgess) | Sector Model (Hoyt) | Multiple Nuclei (Harris/Ullman) |
| Growth Driver | Distance from CBD | Transportation corridors | Functional specialization |
| Shape | Concentric Rings | Wedges/Sectors | Irregular patches |
| CBD Role | Sole dominant center | Dominant but directional | One of many nuclei |
| Applicability | Early industrial cities | Cities with strong rail/road axes | Modern sprawling metropolises |
Modern Concepts in Urban Geography
- Primate City (Mark Jefferson): A city that is at least twice as large as the second-ranking city and overwhelmingly dominant in the national economy (e.g., London, Paris, Bangkok).
- Rank-Size Rule (G.K. Zipf): States that the population of the nth largest city should be 1/n the population of the largest city.
- Urban Sprawl: The unrestricted growth of housing, commercial development, and roads over large expanses of land, with little concern for urban planning.
- Gentrification: The process where wealthy individuals move into distressed urban neighborhoods, leading to property rehabilitation but often displacing lower-income residents.
Trivia for UPSC Prelims
- Megacity: A city with a population exceeding 10 million (e.g., Tokyo, Delhi, Shanghai).
- Conurbation: A term coined by Patrick Geddes for a region where several cities have merged into one continuous built-up area.
- Census Town vs. Statutory Town: A Statutory Town is notified by law (Municipality/Corporation), whereas a Census Town is identified based on demographic criteria (Population >5000, 75% non-agricultural male workforce, Density >400/km2).