Street-network Sprawl in Sanaag, Somalia

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.

Sanaag: region in Somalia

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 Sanaag, Somalia on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Sanaag as of 2014, the overall level of street-network sprawl is 1.89, which is relatively well-connected.

Trends in street network construction: The SNDis of street construction for the respective time periods are 1.26, 2.27, 2.18 and 2.49. Disconnectivity in street construction in Sanaag follows a zig-zag trend. In 1975, street construction was most disconnected, while construction was most connected in 2001-2014.

Quantity of street network construction: The street network in Sanaag spans a total of 2539 kilometers. It is dominated by roads constructed in 1976-1990. These roads have an SNDi of 2.27, 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 1.26, 1.95, 1.94 and 1.89. The aggregate street network in Sanaag increased in disconnectivity initially,but the trend has turned around after 1990.

The level of street-network sprawl in new development in Sanaag followed a zig-zag trend with an overall increase. To get a sense of how street development has changed in Sanaag, we can consider one of its most populous cities: Erigavo. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in new development in Erigavo was at its lowest in 1976-1990.

How do development practices in Sanaag fare in comparison to others in Somalia? Most recently in 2001-2014, street construction in Sanaag was the 6th-most disconnected out of the 16 regions in Somalia. Its position in the ranks since 1975 has risen; relative to other regions in Somalia, street construction in Sanaag has become more disconnected. Sanaag ranked 8th in 1975, 8th in 1976-1990, 8th in 1991-2000 and 6th in 2001-2014.

As of 2014, the city with the most disconnected street network in Sanaag is Erigavo with an SNDi of 1.13, which is relatively well-connected. Conversely, the most connected city is Erigavo with an SNDi of 1.13, which is relatively well-connected. See trends for these cities: Erigavo, Erigavo

The level of street-network sprawl in the aggregate network in Sanaag peaked in 1976-1990. To get a sense of how the aggregate street network has changed in Sanaag, we can consider one of its most populous cities: Erigavo. None of the most populous cities follow the same trend as the region. The level of street-network sprawl in the aggregate network in Erigavo was at its lowest in 1976-1990.

To date, Sanaag is the 11th-most disconnected out of the 16 regions in Somalia. Its position in the ranks since 1975 has fallen; relative to other regions in Somalia, the street network in Sanaag has become more connected. Sanaag ranked 8th in 1975, 10th in 1976-1990, 12th in 1991-2000 and 11th in 2001-2014.