Street-network Sprawl in North Darfur, Sudan

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.

North Darfur: region in Sudan

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 North Darfur, Sudan on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in North Darfur as of 2014, the overall level of street-network sprawl is 1.84, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 0.75, 0.77, 4.02 and 2.61. Street construction in North Darfur increased in disconnectivity initially but has since improved. The streets constructed in 1991-2000 were the most disconnected.

Quantity of street network construction: The street network in North Darfur spans a total of 2257 kilometers. It is dominated by roads constructed in 2001-2014. These roads have an SNDi of 2.61, 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 0.75, 0.73, 0.95 and 1.84. The SNDi of the aggregate street network in fell at first, but North Darfur has worsened in disconnectivity since 1990.

The level of street-network sprawl in new development in North Darfur peaked in 1991-2000. To get a sense of how street development has changed in North Darfur, we can consider three of its most populous cities: Al-Fashir, Saraf `Umrah and Mellit. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Al-Fashir followed a zig-zag trend with an overall decrease. The level of street-network sprawl in new development in Saraf `Umrah followed a zig-zag trend. The level of street-network sprawl in new development in Mellit followed a zig-zag trend with an overall decrease.

How do development practices in North Darfur fare in comparison to others in Sudan? Most recently in 2001-2014, street construction in North Darfur was the 3rd-most disconnected out of the 17 regions in Sudan. Its position in the ranks since 1975 has risen; relative to other regions in Sudan, street construction in North Darfur has become more disconnected. North Darfur ranked 11th in 1975, 12th in 1976-1990, 3rd in 1991-2000 and 3rd in 2001-2014.

As of 2014, the city with the most disconnected street network in North Darfur is Saraf `Umrah with an SNDi of 1.73, which is relatively well-connected. Conversely, the most connected city is Al-Fashir with an SNDi of -0.01, which is very well-connected. See trends for these cities: Al-Fashir, Saraf `Umrah

The level of street-network sprawl in the aggregate network in North Darfur was at its lowest in 1976-1990. To get a sense of how the aggregate street network has changed in North Darfur, we can consider three of its most populous cities: Al-Fashir, Saraf `Umrah and Mellit. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Al-Fashir was at its lowest in 1976-1990. The level of street-network sprawl in the aggregate network in Saraf `Umrah followed a zig-zag trend. The level of street-network sprawl in the aggregate network in Mellit fell steadily.

To date, North Darfur is the 10th-most disconnected out of the 17 regions in Sudan. Its position in the ranks since 1975 has risen; relative to other regions in Sudan, the street network in North Darfur has become more disconnected. North Darfur ranked 11th in 1975, 13th in 1976-1990, 11th in 1991-2000 and 10th in 2001-2014.