Street-network Sprawl in Sarh, Chad

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.

Sarh: city in Moyen-Chari, Chad

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 Sarh, Chad on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Sarh as of 2014, the overall level of street-network sprawl is -0.53, which is very well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are -0.6, nan, -0.45 and -0.3. Data was not available in 1976-1990.

Quantity of street network construction: The street network in Sarh spans a total of 324 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of -0.6, which is very well-connected.

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 -0.6, -0.6, -0.57 and -0.53. The SNDi of the aggregate street network in fell at first, but Sarh has worsened in disconnectivity since 1990.

Sarh and Moyen-Chari do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in Moyen-Chari rose steadily.

How do development practices in Sarh fare in comparison to others in Moyen-Chari? Most recently in 2001-2014, street construction in Sarh was the 2nd-most disconnected out of the 2 cities in Moyen-Chari. Its position in the ranks since 1975 has fallen; relative to other cities in Moyen-Chari, street construction in Sarh has become more connected. Sarh ranked 1st in 1975, 1st in 1991-2000 and 2nd in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

Sarh and Chad do not follow the same trend in the disconnectivity of their street network constructions. There was not enough data from the city, while the SNDi of street constructions in Chad peaked in 1976-1990.

How do development practices in Sarh fare in comparison to others in Chad? Most recently in 2001-2014, street construction in Sarh was the 16th-most disconnected out of the 26 cities in Chad. Its position in the ranks since 1975 has fallen; relative to other cities in Chad, street construction in Sarh has become more connected. Sarh ranked 7th in 1975, 14th in 1991-2000 and 16th in 2001-2014. There was no ranking in 1976-1990 due to unavailable data.

Sarh and Moyen-Chari do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Sarh was at its lowest in 1976-1990, while the SNDi of street constructions in Moyen-Chari rose steadily.

To date, Sarh is the 2nd-most disconnected out of the 2 cities in Moyen-Chari. Its position in the ranks since 1975 has fallen; relative to other cities in Moyen-Chari, the street network in Sarh has become more connected. Sarh ranked 1st in 1975, 1st in 1976-1990, 1st in 1991-2000 and 2nd in 2001-2014.

Sarh and Chad do not follow the same trend in the disconnectivity of their aggregate street networks. The SNDi in Sarh was at its lowest in 1976-1990, while the SNDi of street constructions in Chad rose steadily.

To date, Sarh is the 22nd-most disconnected out of the 26 cities in Chad. Its position in the ranks since 1975 has fallen; relative to other cities in Chad, the street network in Sarh has become more connected. Sarh ranked 7th in 1975, 14th in 1976-1990, 15th in 1991-2000 and 22nd in 2001-2014.

As of 2015, Sarh had a built-up area of 11.7 square kilometers, and a population of 329481 people.

These are some other cities with approximately the same population: