Street-network Sprawl in KwaZulu-Natal, South Africa

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:

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:

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

KwaZulu-Natal: region in South Africa

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 KwaZulu-Natal, South Africa on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in KwaZulu-Natal as of 2014, the overall level of street-network sprawl is 5.4, which is highly disconnected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 3.03, 5.27, 6.27 and 6.28. In each period, new street development in KwaZulu-Natal steadily grows more disconnected than in the last. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 2.25 points, but between 1991-2000 and 2001-2014, it rose by just 0.01.

Quantity of street network construction: The street network in KwaZulu-Natal spans a total of 57817 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 6.28, which is highly disconnected.

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 3.03, 4.91, 5.16 and 5.4. Overall, the SNDi of the aggregate street network has risen: the street network in KwaZulu-Natal has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 1.88 points, but between 1991-2000 and 2001-2014, it rose by just 0.24.

The level of street-network sprawl in new development in KwaZulu-Natal rose steadily. To get a sense of how street development has changed in KwaZulu-Natal, we can consider three of its most populous cities: Durban, Edendale and Osizweni. Out of the three cities, Durban and Osizweni do not follow the same trend as the region. The level of street-network sprawl in new development in Durban peaked in 1991-2000. The level of street-network sprawl in new development in Osizweni followed a zig-zag trend with an overall increase.

How do development practices in KwaZulu-Natal fare in comparison to others in South Africa? Most recently in 2001-2014, street construction in KwaZulu-Natal was the 1st-most disconnected out of the 9 regions in South Africa. Its position in the ranks since 1975 has risen; relative to other regions in South Africa, street construction in KwaZulu-Natal has become more disconnected. KwaZulu-Natal ranked 3rd in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.

As of 2014, the city with the most disconnected street network in KwaZulu-Natal is Sikhalasenkosi with an SNDi of 6.33, which is highly disconnected. Conversely, the most connected city is Osizweni with an SNDi of 1.91, which is relatively well-connected. See trends for these cities: Osizweni, Sikhalasenkosi

The level of street-network sprawl in the aggregate network in KwaZulu-Natal rose steadily. To get a sense of how the aggregate street network has changed in KwaZulu-Natal, we can consider three of its most populous cities: Durban, Edendale and Osizweni. Out of the three cities, Osizweni does not follow the same trend as the region. The level of street-network sprawl in the aggregate network in Osizweni was at its lowest in 1976-1990.

To date, KwaZulu-Natal is the 1st-most disconnected out of the 9 regions in South Africa. Its position in the ranks since 1975 has risen; relative to other regions in South Africa, the street network in KwaZulu-Natal has become more disconnected. KwaZulu-Natal ranked 3rd in 1975, 1st in 1976-1990, 1st in 1991-2000 and 1st in 2001-2014.