If you worry that your neighbourhood is going downhill, there could be a way to spot the signs before it happens. You might unwittingly be living in an area designed to foster crime, deprivation and ghettoisation, according to two mathematicians who have developed a method to spot hidden areas of geographical isolation in the urban landscape.
Many neighbourhoods are cut off from other parts of the city by poor transport links and haphazard urban planning, which can often lead to social ills. “Geographical isolation is a prime cause of social deprivation, economic inactivity and crime,” says Dimitry Volchenkov at the University of Bielefeld in Germany.
“Geographical isolation is a prime cause of social deprivation, economic inactivity and crime, but can be hard to quantify”
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Sociologists think that isolation worsens an area’s economic prospects by reducing opportunities for commerce, and engenders a sense of isolation in inhabitants, both of which can fuel poverty and crime. For example, Laura Vaughan at University College London analysed street-by-street poverty in London over the past century and showed that inaccessible areas attract poorer inhabitants (World Architecture, vol 185, p 88).
Unfortunately, urban planners and governments have often failed to take such isolation into account when shaping the city landscape, not least because isolation can sometimes be difficult to quantify in the complex fabric of a major city.
Now Volchenkov and colleague Philippe Blanchard have created an algorithm that aims to capture a neighbourhood’s inaccessibility, which they claim could expose hidden islands of future deprivation in cities ().
To test their equations, Volchenkov and Blanchard analysed how easy it is to get to various places on the labyrinthine network of canals in Venice, Italy. They chose the city because its 96 canals, which snake around 122 small islands, provided a simple model to test the method. For their calculations, they imagined gondoliers dispersing randomly along the canals, as if they were drunk. This allowed them to work out the average number of random turns at junctions it would take to reach any particular place in Venice from various starting points.
Not surprisingly, the Grand Canal, the giant Giudecca Canal and the Venetian Lagoon were the most connected, says Volchenkov (see Map). In contrast, the researchers found that one district – the Venetian Ghetto – jumped out as by far the most isolated, despite being apparently well connected to the rest of the city. “On average, it took 300 random steps to reach, far more than the average of 100 steps for other places in Venice,” says Volchenkov.
The Ghetto was created in March 1516 to separate Jews from the Christian majority of Venice. It persisted until 1797, when Napoleon conquered the city and demolished the Ghetto’s gates. “You would never guess that the Ghetto was the most isolated district from the geography of Venice,” says Volchenkov.
Although Venice was a simple place to analyse, Volchenkov says that their method could easily be used to identify isolated neighbourhoods in big cities with a complex web of roads, walkways and public transport systems.
For example, he believes that the Bowery, which was a deprived district of New York for most of the 20th century, might have been isolated from nearby areas at the time. “In existing cities, efforts should be made to reconnect isolated districts, perhaps by building tunnels and bridges,” Volchenkov says.
Geoffrey Ingarfield, a housing expert at Middlesex University in London, points to an example in the UK where planners did the opposite in the 1970s, upgrading a major road and splitting a neighbourhood in two. “The widening of the A13 in Newham, London, completely isolated the area to the immediate south, causing shops and the last secondary school to close,” he says. “Unable to cross the road, the people to the south became more isolated and socially deprived.”
