Street-network Sprawl in Quzhou, China

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What is Street-network sprawl?

Street-network Sprawl is a way to measure urban sprawl, worldwide, through the connectedness of the streets. Less sprawl means more connected, more walkable streets. Well-connected streets – like New York City’s grid – are more walkable and can be served by public transit.

The street network is permanent, and its connectivity affects the livability and environmental footprint of cities for decades and centuries to come. In places with more connected streets, residents drive less and walk more. A well-connected street network is associated with better outcomes for health, the environment, sustainable consumption, social integration, and equity.

We can quantify how connected street networks are with the Street Network Disconnectedness Index (SNDi).

SNDi -- our measure of street-network sprawl (disconnectedness)

The SNDi is a comprehensive measurement of “sprawl”. It captures:

• nodal degree
• dendricity, the tree-likeness of the street network
• circuity, the ratio of the distance by road to the straight-line distance of two locations on the street network
• sinuosity, the curviness of a street

A higher SNDi means less-connected streets – i.e., more sprawl. For the 10137 cities in our dataset, the average SNDi is 2.25, with half of the cities' SNDis falling between 1.08 and 3.25.

More information on the sprawl index can be found in these research papers:

• Global trends toward urban street-network sprawl
• A global assessment of street-network sprawl

To see the state of street-network sprawl across the globe, visit the sprawlmap.

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Quzhou: city in Zhejiang, China

What exactly constitutes the spatial extent of the city? For these aggregations, we used the Global Human Settlement Layer Urban Center Database (GHS-UCDB) to define the boundaries of the city. These cities -- or urban centers -- cover areas that are densely populated and built-up, and so may extend beyond the spatial borders of these cities that we may be familiar with. The GHS area is shaded in blue.

View Quzhou, China on the sprawlmap

How have Quzhou's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Quzhou as of 2014, the overall level of street-network sprawl is 2.44, which is in the 40th to 60th percentile of disconnectedness.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.0, 2.54, 1.17 and 2.73. The disconnectivity of new streets constructed in Quzhou fell, then rose. In 1991-2000, new street layouts were the most connected.

Quantity of street network construction: The street network in Quzhou spans a total of 730 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 2.54, which is in the 40th to 60th percentile of disconnectedness.

Effect on the aggregate network: New construction in each period adds to the total stock of streets, but does not change streets that have already been built. Therefore, it has a limited effect on the street network as a whole. The SNDis of the aggregate street network in the respective time periods are 3.0, 2.57, 2.19 and 2.44. The SNDi of the aggregate street network in fell at first, but Quzhou has worsened in disconnectivity since 2000.

Quzhou in context: Street-network sprawl of new development

Quzhou and Zhejiang do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Quzhou was at its lowest in 1991-2000, while the SNDi of street constructions in Zhejiang peaked in 1976-1990.

How do development practices in Quzhou fare in comparison to others in Zhejiang? Most recently in 2001-2014, street construction in Quzhou was the 28th-most disconnected out of the 94 cities in Zhejiang. Its position in the ranks since 1975 has fallen; relative to other cities in Zhejiang, street construction in Quzhou has become more connected. Quzhou ranked 17th in 1975, 25th in 1976-1990, 43rd in 1991-2000 and 28th in 2001-2014.

Quzhou and China do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Quzhou was at its lowest in 1991-2000, while the SNDi of street constructions in China followed a zig-zag trend with an overall decrease.

Quzhou in context: Aggregate street-network sprawl

Quzhou and Zhejiang do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Quzhou was at its lowest in 1991-2000, while the SNDi of street constructions in Zhejiang peaked in 1976-1990.

To date, Quzhou is the 26th-most disconnected out of the 94 cities in Zhejiang. Its position in the ranks since 1975 has fallen; relative to other cities in Zhejiang, the street network in Quzhou has become more connected. Quzhou ranked 17th in 1975, 24th in 1976-1990, 34th in 1991-2000 and 26th in 2001-2014.

Quzhou and China do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Quzhou was at its lowest in 1991-2000, while the SNDi of street constructions in China peaked in 1976-1990.

What about other similarly-populated cities?

As of 2015, Quzhou had a built-up area of 43.72 square kilometers, and a population of 376284 people.

These are some other cities with approximately the same population:

• Hawassa, Ethiopia
• Brick, United States
• Sidhi, India