Street-network Sprawl in Dakhlet Nouadhibou, Mauritania

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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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Dakhlet Nouadhibou: region in Mauritania

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 Dakhlet Nouadhibou, Mauritania on the sprawlmap

How have Dakhlet Nouadhibou's street networks changed over time?

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Dakhlet Nouadhibou as of 2014, the overall level of street-network sprawl is 1.01, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.01, 0.76, 0.0 and 0.16. The disconnectivity of new streets constructed in Dakhlet Nouadhibou fell, then rose. In 1991-2000, new street layouts were the most connected.

Quantity of street network construction: The street network in Dakhlet Nouadhibou spans a total of 423 kilometers. It is dominated by roads constructed prior to 1975. These roads have an SNDi of 2.01, which is relatively 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 2.01, 1.89, 1.27 and 1.01. Overall, the SNDi of the aggregate street network has fallen: the street network in Dakhlet Nouadhibou has become more connected. This decrease has quickened: between 1975 and 1976-1990, SNDi fell by 0.13 points, but between 1991-2000 and 2001-2014, it fell by just 0.26.

Dakhlet Nouadhibou in context: Street-network sprawl of new development

The level of street-network sprawl in new development in Dakhlet Nouadhibou was at its lowest in 1991-2000. To get a sense of how street development has changed in Dakhlet Nouadhibou, we can consider one of its most populous cities: Nouadhibou. Disconnectivity in the most populous cities in Dakhlet Nouadhibou follow the same region trend.

How do development practices in Dakhlet Nouadhibou fare in comparison to others in Mauritania? Most recently in 2001-2014, street construction in Dakhlet Nouadhibou was the 6th-most disconnected out of the 6 regions in Mauritania. Its position in the ranks since 1975 has fallen; relative to other regions in Mauritania, street construction in Dakhlet Nouadhibou has become more connected. Dakhlet Nouadhibou ranked 3rd in 1975, 4th in 1976-1990, 6th in 1991-2000 and 6th in 2001-2014.

Dakhlet Nouadhibou in context: Aggregate street-network sprawl

As of 2014, the city with the most disconnected street network in Dakhlet Nouadhibou is Nouadhibou with an SNDi of 0.54, which is relatively well-connected. Conversely, the most connected city is Nouadhibou with an SNDi of 0.54, which is relatively well-connected. See trends for these cities: Nouadhibou, Nouadhibou

The level of street-network sprawl in the aggregate network in Dakhlet Nouadhibou fell steadily. To get a sense of how the aggregate street network has changed in Dakhlet Nouadhibou, we can consider one of its most populous cities: Nouadhibou. Disconnectivity in the most populous cities in Dakhlet Nouadhibou follow the same region trend.

To date, Dakhlet Nouadhibou is the 5th-most disconnected out of the 6 regions in Mauritania. Its position in the ranks since 1975 has fallen; relative to other regions in Mauritania, the street network in Dakhlet Nouadhibou has become more connected. Dakhlet Nouadhibou ranked 3rd in 1975, 3rd in 1976-1990, 4th in 1991-2000 and 5th in 2001-2014.

Cities in Dakhlet Nouadhibou

• Nouadhibou