Urban expansion or suburban expansion, is a process of suburban urbanisation in which the urban population grows significantly outward, encroaching on the rural areas on the urban fringe and creating low-density, monofunctional, often car-dependent communities. In addition to describing the pattern of a particular urbanisation process, the term also often relates to its social and environmental consequences.

For example, Batty defines sprawl as 'uncoordinated growth: the expansion of communities without regard to consequences; in short, unplanned, incremental urban growth that is often considered unsustainable.’ Bhatta wrote in 2010 that while the exact definition of sprawl is debated, it is 'widely accepted that urban sprawl is characterised by a pattern of unplanned and uneven growth, which is driven by multiple processes and leads to inefficient use of resources. '

Urban History

Population

Population Density in Los Angeles County

Los Angeles has experienced significant urban expansion since the late 20th century, with population density escalating particularly in the metropolitan areas. This growth has not only redefined the cityscape but has also pushed the boundaries of urban planning and sustainability.

Try Interactive Map

Metro Rail Change

Los Angeles once had the world's largest tram system, with the famous "Red Cars" of the Pacific Electric Railway and the "Yellow Cars" of the Los Angeles Railway. However, as cars became more common and the city grew, the tram system declined. Starting in the 1950s, suburbanization and highway construction reduced tram demand, leading to service closures or conversions to buses.
In the 1980s, LA faced severe traffic congestion. To combat this, the government levied sales taxes to build a new rail network. The A Line opened in 1990, marking rail transit's return. Subsequent years saw the opening of underground railways and more light rail lines, including the first underground line in 1993.
As the city expanded, LA's rail network grew, with lines like the C Line (1995), E Line (2012), and K Line (2022). These projects aimed to improve public transit and ease congestion.


---- A line (1990)
---- B&D lines (1993)
---- C line (1995)
---- E line (2012)
---- K line and others which are still under construction



*Note that:
1. B & D Lines are combined together.
2. The Airport Metro Connector and Aviation/Century Station of K line won’t be in service until late 2024



Data From: LA Metro

1

Human Settlement Built-up Areas Change
1975-2020

The images illustrate the changes in the distribution of human settlement built-up surfaces in Los Angeles over a period of 45 years, with data covering both the total built-up surface and the built-up surface allocated to dominant non-residential (NRES) uses.

Image showing changes in built-up areas
1975

*Using the WGS84 coordinate system, with a resolution of 3 arcseconds.

Data From: GHSL

We can observe that with the increase in years, there are more white areas visible within the image, especially at the boundaries, indicating continuous expansion of the city over the 45-year period.
In the late 19th and early 20th centuries, with the discovery of oil, Los Angeles began to rise and rapidly developed into the largest city in the American West. After World War II, the rise of modern industry, commerce, finance, and tourism flourished, and the urban area continued to expand outward. Even though the city was already very prosperous before 1975, as shown in the image, the urban architecture continued to expand after that year.

Sustainablity in Los Angeles

Trends in different type of Air Quality Days (1980-2020)

According to the United States Environmental Protection Agency (EPA), various air quality indicators are used to classify air quality into different categories such as Good Days, Moderate Days, and Unhealthy Days.
This line graph illustrates the annual count of days classified as 'Moderate' in terms of air quality from 1980 to 2020. The data provides insight into the fluctuations and trends in air quality over four decades.

We can see that the number of days with good air quality has been increasing year by year, while unhealthy days do not show such a steady trend. In 2010, there was a trough in unhealthy days, and at the same time, we can see a peak in moderate days in the same year, which is somewhat strange.

One possible explanation is the National Ambient Air Quality Standards (NAAQS) established in 2008, which scientists considered too loose, resulting in some days that should have been classified as unhealthy being categorized as moderate. This also led to the public not being alerted to these days of unhealthy air. Subsequently, based on the unanimous recommendation of the independent board of air experts and scientists established under the Clean Air Act, the standards were updated in 2013, which to some extent explains why there were no more seemingly 'abnormal' data in 2020.

Read More
Annual AQI data of LA

Data From: epa.gov

PM2.5 & Water Quality

PM2.5, consisting of fine particulate matter from vehicles and industrial activities, poses substantial health risks, particularly in rapidly growing urban centers such as Los Angeles. Alongside water quality, these environmental factors are crucial for monitoring to safeguard public health and guide infrastructural decisions.
Try Interactive Map

Conclusion

Over the past century, Los Angeles has experienced rapid growth from a small county of 50,000 people to the largest county in the western United States. This rapid expansion has placed significant environmental pressures on the city.

In recent years, Los Angeles has dedicated itself to sustainable development, aiming to strike a balance between environmental protection and urban growth. Measures such as promoting green buildings and enhancing public transportation have been implemented to improve air and water quality. As a result, Los Angeles has become a global model for sustainable development.

CASA003 Group Work © Click Here to visit the GitHub Repository