Street-network Sprawl in Ghardaïa, Algeria

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.

Ghardaïa: region in Algeria

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 Ghardaïa, Algeria on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Ghardaïa 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 2.34, 2.18, 2.92 and 2.32. Disconnectivity in street construction in Ghardaïa follows a zig-zag trend. In 1976-1990, street construction was most disconnected, while construction was most connected in 1991-2000.

Quantity of street network construction: The street network in Ghardaïa spans a total of 1712 kilometers. The period with the greatest volume of street construction was 2001-2014. These roads have an SNDi of 2.32, 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 2.34, 2.23, 2.38 and 2.44. The SNDi of the aggregate street network in fell at first, but Ghardaïa has worsened in disconnectivity since 1990.

The level of street-network sprawl in new development in Ghardaïa followed a zig-zag trend with an overall decrease. To get a sense of how street development has changed in Ghardaïa, we can consider three of its most populous cities: Ghardaia, El Menia and Guerrara. Out of the three cities, Ghardaia does not follow the same trend as the region. The level of street-network sprawl in new development in Ghardaia rose steadily.

How do development practices in Ghardaïa fare in comparison to others in Algeria? Most recently in 2001-2014, street construction in Ghardaïa was the 28th-most disconnected out of the 46 regions in Algeria. Its position in the ranks since 1975 has fallen; relative to other regions in Algeria, street construction in Ghardaïa has become more connected. Ghardaïa ranked 18th in 1975, 19th in 1976-1990, 16th in 1991-2000 and 28th in 2001-2014.

As of 2014, the city with the most disconnected street network in Ghardaïa is Ghardaia with an SNDi of 2.69, which is in the 40th to 60th percentile of disconnectedness. Conversely, the most connected city is Guerrara with an SNDi of 1.49, which is relatively well-connected. See trends for these cities: Guerrara, Ghardaia

The level of street-network sprawl in the aggregate network in Ghardaïa was at its lowest in 1976-1990. To get a sense of how the aggregate street network has changed in Ghardaïa, we can consider three of its most populous cities: Ghardaia, El Menia and Guerrara. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Ghardaia rose steadily. The level of street-network sprawl in the aggregate network in El Menia fell steadily. The level of street-network sprawl in the aggregate network in Guerrara followed a zig-zag trend with an overall decrease.

To date, Ghardaïa is the 16th-most disconnected out of the 46 regions in Algeria. Its position in the ranks since 1975 has risen; relative to other regions in Algeria, the street network in Ghardaïa has become more disconnected. Ghardaïa ranked 18th in 1975, 17th in 1976-1990, 15th in 1991-2000 and 16th in 2001-2014.