Comprehensive Urban Patterns and Structures Study Guide

Historical Trends in Global Urbanization

Global settlement patterns have shifted dramatically over the past two centuries, reflecting a steady movement from rural to urban living. In the year $1800$, only $1\%$ of the global population lived in cities. This figure grew to $6\%$ by the year $1850$, reached $14\%$ by the year $1900$, and increased significantly to $30\%$ by $1950$. By the start of the new millennium in $2000$, urban dwellers accounted for $47\%$ of the population. A major milestone was reached in $2008$, when the total population of urban settlements exceeded that of rural settlements for the first time in human history. As of $2019$, the percentage has reached approximately $55\%$.

Central Business District (CBD) Land Use and Service Clustering

The Central Business District, or CBD, is the nucleus of the modern city. While it typically occupies less than $1\%$ of the total urban land area, it contains a disproportionately large percentage of the city's overall services. These services are categorized into three primary types. Public Services include essential civic infrastructure such as city hall, courts, state and county agencies, and public libraries. These are centrally located to ensure maximum accessibility for all residents. To stimulate downtown commerce, sports centers and convention centers, such as those found in the Deer District, are often situated in the CBD. Business Services, such as advertising agencies, banks, financial institutions, and law firms, cluster in the CBD to facilitate fac-to-face meetings and professional collaboration. Finally, Consumer Services historically defined the CBD through high-threshold retailers, high-range retailers, and services catering to downtown workers. However, changing shopping habits and the migration of affluent citizens to the suburbs have notably reduced the dominance of retail in the central core.

Vertical Development and Competition for CBD Land

Because demand for land in the CBD is extreme and the supply is limited, the value of land remains high, which has encouraged vertical development in two directions. The Underground CBD exists because there is inadequate space above ground for the massive networks of telephone, electric, and broadband cables. Subterranean passages also serve to segregate pedestrian traffic from motor vehicles and provide protection from harsh winter weather conditions. Above ground, High-rise Skyscrapers have become the standard solution for accommodating dense activities in an economically feasible manner, often visualized in landmarks like Bears Stadium.

The Burgess Concentric Zone Model

The Concentric Zone Model, first developed by Burgess, was the initial framework designed to explain how social groups are distributed across urban areas. This model posits that cities grow outward from a central point in five distinct rings. Zone 1 is the Central Business District. Zone 2 is the Zone of Transition, which contains industry and lower-quality housing. Zone 3 is the Zone of Independent Workers' Homes, characterized by modest, older houses occupied by the working class. Zone 4, the Zone of Better Residences, contains newer and more spacious houses for the middle class. Zone 5 is the Commuter's Zone, which represents the outermost residential area beyond the continuous built-up city.

The Hoyt Sector Model

The Sector Model, proposed by Hoyt, suggests that cities develop in a series of sectors or wedges rather than perfect rings. Historically, certain areas become attractive for specific activities, and as the city grows, these activities expand outward in a wedge-like shape from the center. The sectors typically include the CBD (A), the Zone of Transition (B), Lower-class Residential (C), Middle-class Residential (D), Upper-class Residential (E), and Industry (F).

The Multiple Nuclei Model

The Multiple Nuclei Model recognizes the city as a complex structure containing more than one center around which various activities revolve. This model accounts for the fact that certain activities are attracted to specific nodes while avoiding others. For instance, heavy manufacturing and high-class housing naturally gravitate toward different centers. This model suggests the CBD has lost its status as the singular nucleus. The specialized nodes include the CBD (1), Wholesale and Light Manufacturing (2), Low-class Residential (3), Medium-class Residential (4), High-class Residential (5), Heavy Manufacturing (6), Outlying Business District (7), Residential Suburbs (8), and Industrial Suburbs (9).

Geographic Context and Applications of Urban Models

While these models provide a lens for understanding why different social characteristics are distributed in certain patterns, critics argue they are too simple or dated to explain modern urbanism. Geographers often combine these models to gain accuracy. Generally, people prefer to live near those with similar characteristics. Application of the Concentric Zone Model suggests that families in newer homes occupy outer rings, while those in older homes occupy inner rings. The Sector Model implies that families of different income levels will rarely share the same sector. The Nuclei Model suggests that individuals from the same ethnic background are likely to cluster near one another.

International Comparisons: Urban Models in Europe and Developing Countries

Urban patterns differ significantly outside of North America. In European cities, the wealthy often reside in the inner portions of the upper-class sectors, whereas in the U.S., the affluent tend to live in the suburbs. Furthermore, suburban development in Europe frequently consists of high-rise apartment complexes designed for low-income residents and recent immigrants, a sharp contrast to the detached single-family homes found in American suburbs. In developing countries, the pattern is often inverted compared to the U.S.: the poor occupy the outskirts, while the wealthy live near the city center and along an elite commercial sector extending from the center.

The Southeast Asian City (McGee) Model

The McGee Model describes the structure of Southeast Asian cities. These cities generally lack a single traditional CBD. Instead, components of the CBD are dispersed across several areas including the old colonial port, the Western commercial zone (WC), and the alien commercial zone (AC). The structure includes a port zone at its heart, government zones, hybrid mixed land use zones, and new industrial estates on the city's outskirts. It also features market gardening zones and peripheral squatter areas.

The Latin American City (Griffin-Ford) Model

The Griffin-Ford model explains cities in Latin America, which are structured around a core CBD attached to a commercial "spine." This spine is surrounded by elite housing and high-end services like malls. The rest of the city consists of three concentric zones that decrease in housing quality as they move outward: the Zone of Maturity, the Zone of In Situ Accretion, and the Periférico (peripheral squatter settlements). These cities also include disamenity zones and areas of gentrification.

The Sub-Saharan African City (De Blij) Model

The De Blij model highlights the impact of European colonialism on Sub-Saharan African cities. A central characteristic is the presence of three distinct CBDs: a former Colonial CBD with high-rise development, a Traditional CBD with one-story buildings, and a Market CBD which serves as an open-air, informal commerce hub. These are surrounded by ethnic and mixed neighborhoods, mining and manufacturing zones, and informal satellite towns or townships.

Defining Urban Settlements: Cities, Urban Areas, and MSAs

Urban settlements are defined in several ways. A city is a legally incorporated, self-governing unit, often called a central city in the U.S. An Urban Area consists of a dense core of census tracts and suburbs; this is subdivided into an Urbanized Area (population of at least $50,000$) and an Urban Cluster (population between $2,500$ and $50,000$). To measure a city's functional area, the U.S. Bureau of the Census uses the Metropolitan Statistical Area (MSA). An MSA includes an urbanized area of at least $50,000$ people, the county it resides in, and adjacent counties with high population densities and large percentages of residents commuting into the central county.

Megalopolis and Local Government Fragmentation

When multiple MSAs overlap, they form a continuous urban complex known as a Megalopolis. Geographer Jean Gottmann named the region from North of Boston to South of Washington D.C. as the primary example of this "great city" phenomenon. To manage the resulting local government fragmentation, many regions utilize a Council of Government, a cooperative agency that performs overall planning functions that single local governments cannot manage alone.

Categorizing Urban Growth: Edge Cities, Boomburbs, and Exurbs

As urban areas expand, new types of settlements emerge. An Edge City is a large node of retail and office activities situated on the periphery of an urban area, such as Austin. A Boomburb is a rapidly growing suburban city that has developed its own distinct identity. An Exurb is a settlement located outside a suburban area that maintains a functional connection to the city.

Megacities, Metacities, and Global Population Distribution

The scale of urban environments is categorized by population size. A Megacity is defined as a city with a population greater than $10$ million. A Metacity has a population exceeding $20$ million. Globally, $46.0\%$ of people remain in rural areas. Among urban residents, population is distributed across small cities (between $300,000$ and $1$ million inhabitants), medium cities ($1$ to $5$ million), large cities ($5$ to $10$ million), and megacities, which currently house $6.4\%$ of the global population.

Global Rankings: The World's Most Populated Cities

According to the UN, the world's most populated cities include Tokyo, Japan ($38$ million), Delhi, India ($25$ million), and Mexico City, Mumbai, and São Paulo (each around $21$ million). Osaka has just above $20$ million, followed by Beijing at just below $20$ million. New York-Newark and Cairo both house approximately $18.5$ million. However, alternative data from World Population Review reports higher estimates for some areas: Jakarta, Indonesia ($\sim 42$ million), Dhaka, Bangladesh ($\sim 37$ million), Tokyo ($\sim 33$ million), New Delhi ($\sim 30$ million), Shanghai ($\sim 29$ million), Guangzhou ($\sim 27$ million), Cairo ($\sim 23-25$ million), Manila ($\sim 23-24$ million), Mumbai ($\sim 22$ million), and Seoul ($\sim 22$ million).

Rank-Size Rule versus Primate City Urban Systems

Urban systems generally follow one of two patterns. The Rank-Size Rule states that the $n^{th}$ largest city is $1/n$ the size of the largest city (e.g., the second largest is $1/2$ the size of the first, and the fourth is $1/4$). For instance, if the largest city has $100,000$ people, the second would have $50,000$. Conversely, a Primate City system exists when the largest city is more than double the size of the second largest, such as a largest city of $100,000$ compared to a second largest of $10,000$.

Mechanisms of Urban Expansion: Annexation and Density Gradients

Annexation is the legal process of adding land area to a city, which was common in the $19^{th}$ century as cities offered superior services like sewage and water. The Density Gradient refers to the phenomenon where U.S. cities become less dense the farther one travels from the center. In recent years, this gradient has transitioned toward flattening as population and services spread more evenly across larger areas.

Suburban Sprawl and Segregation through Zoning

Suburban sprawl is the progressive, often disorganized spread of development across the landscape. Modern U.S. suburbs are typically segregated in two ways. Social Class segregation occurs because similarly priced houses are built together, attracting specific income ranges. Land Use segregation is maintained through zoning ordinances, which ensure residential areas are physically separated from commercial and manufacturing activities.

Urban Transportation: Space Allocation and Alternative Fuels

Motor vehicles have enabled the large-scale development of distant suburbs. In typical U.S. cities, approximately $1/4$ of all land is dedicated to roads and parking lots. Multi-lane freeways can cut a $23$-meter ($75$-foot) path through a city. To combat the pollution of congestion, automakers are developing alternative fuels: Diesel (efficient and usable with biodiesel), Hybrids (recapturing energy during braking), Ethanol (distilled from crops like corn or sugarcane), Plug-in Hybrids, and Hydrogen Fuel Cells using a Polymer Electrolyte Membrane (PEM) to combine hydrogen and oxygen for electricity.

Public Transit: Socioeconomics, Benefits, and Limitations

Public transit is more space and energy-efficient than private vehicles and produces fewer pollutants. However, in the U.S., many overlook these benefits in favor of the privacy and scheduling flexibility of cars. Public transit is unfortunately not offered in many U.S. cities, despite its cost-effectiveness for moving large numbers of people in dense areas.

Urban Decay: Filtering, Redlining, and Public Housing

Deterioration in inner cities involves several processes. Filtering occurs when large old houses are subdivided into multiple dwellings for low-income families, eventually leading to property abandonment by landlords. Redlining is the illegal but difficult-to-enforce practice where banks draw lines on a map and refuse to lend money for home improvements within those boundaries. Public Housing was introduced mid-century as a replacement for substandard housing; residents pay $30\%$ of their income for rent, with the government covering the remainder. High-rise public housing is now generally considered unsatisfactory for families.

Social Realities: Blockbusting and Food Deserts

Blockbusting is an illegal real estate practice where agents convince white homeowners to sell their property by instilling fear that minorities moving in will lower property values; this contributed significantly to "white flight." Additionally, some urban and rural areas suffer from being Food Deserts, which are neighborhoods lacking access to fresh, healthy, and affordable food, often served only by convenience stores and fast food. Detroit, New York, and D.C. are common examples of where these deserts occur.

Urban Influx: Shock Cities and Squatter Settlements

Shock Cities are urban places experiencing massive, rapid urbanization that overwhelms infrastructure, leading to slums, pollution, fires, and social exploitation. Migrants who cannot find housing often build Squatter Settlements (also known as barriadas, barrios, favelas, bidonvilles, or bustees) on the city's edge. These makeshift, unsafe shelters lack paved roads, sewers, and schools, and residents often must steal electricity.

Gentrification: Socioeconomic Drivers and Racial Implications

Gentrification is the process of renewal and reinvestment of capital in inner-city areas. This results in higher property values and often displaces poorer residents with middle-class or affluent newcomers. There is a frequent racial component to this shift, sometimes referred to as the "White Ring Conspiracy," where white populations move out to suburbs and later return to the urban core, displacing minority communities. Local governments often welcome gentrification because it generates higher tax revenues used for city services like police, fire, and school funding. Young professionals and retired suburbanites drive this trend, seeking cultural opportunities and architectural character.

Assessing Gentrification: Indicators and Strategic Moderation

Cities with high gentrification rates include Portland ($53.1\%$ of eligible neighborhoods), Washington D.C. ($51.9\%$), Minneapolis ($50.6\%$), Seattle ($50.0\%$), and Atlanta ($46.2\%$). Gentrification can be measured by tracking changes in property values, tax rates, rental turnover, and the transition from factory to service jobs. To mitigate disadvantages, cities can provide tax relief for long-term homeowners, promote mixed-income housing, support neighborhood organizations, and establish Community Land Trusts (CLTs).

Evaluating Gentrification and the New Urbanism Movement

While gentrification brings infrastructure reinvestment, business expansion, and job opportunities, it also disrupts community institutions and causes racial and economic conflict. As a reaction to sprawl and automobile-centered cities, the New Urbanism movement promotes pedestrian-friendly, mixed-use commercial and residential developments. This movement seeks to create community-oriented cities that are not car-dependent.