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Bosselmann – Urban transformations: cities from a satellite

Steen Eiler Rassmussen might have been the first to use a comparative method to show the continuous urbanization of cities when he explained the difference between Paris’s compact form and London’s sprawling configuration. Sixty years later, the dif-ferences in land coverage between the two cities is less pronounced. Today, the term continuous urbanization takes on a new meaning when applied to urban agglomerations in South East Asia. Around the Pearl River Delta, the cities of Foshan, Guang-zhou (Canton), and Dongguan are now robustly connected with Shenzhen. From Shenzhen to Hong Kong, only some gaps are still visible on recent satellite imagery. Currently, a bridge is planned to cross the Pearl River estuary from Hong Kong to Macao. Once completed, the bridge will close a loop connecting a continuously urbanized area from Macao to Zhulai, Zhongshan to Shunde and back to Foshan. In the Pearl River Delta, in a pattern similar to the Randstad area of Holland, a rim of cities is emerging around bodies of water and agriculture. The number of people living inside this conurbation is conservatively estimated to include 55 million by the United Nations, and is probably much higher.


At present, it is highly relevant to watch the cities of the world from space, and not only the expanding cities of the developing world, but also the shrinking and dispersing cities in the developed world. When comparing the footprints of the world’s largest cities, two observations stand out clearly. The first is that human tolerance for density, defined as the number of people per sur-face area, varies to a stunning degree. The second observation is related to form. There might be increasing similarity when city extensions are viewed on the ground, but when seen from space, it is clear that not two urban agglomerations are the same. The reasons for the distinctive shapes of urban agglomerations are largely related to local landform, especially water systems.


If one were to imagine for a moment that it would be possible to direct the transformation of cities in the developing world, not to stop the influx of rural migration, but to direct the transformation and expansion at their outskirts, future satellite images would show a web of linear gaps in settlement patterns, where now continuous urbanization occurs. These gaps would coincide with the existing water drainage patterns. For reasons that are well understood, new urbanization would stay at a distance from water, from creeks, rivers, bays, and estuaries. Of all physical measures, the preservation of land near water would provide the greatest benefits for human health, the health of vegetation and animal life, the quality of water and air, and a more comfortable climate. The same understanding of natural systems would direct the dispersion of cities in the developed world. In both worlds, the result would lead to a better integration of cities with the forces of nature.


This is not to be misunderstood, for some of the world’s most memorable and intensely urban settings are located on water-fronts, along river embankments, harbour fronts and facing beaches. On the other extreme, we find that the marginal low lying land near flood prone urban waterfronts is home to informal settlements for millions of people. Notwithstanding the beauty of wa-terfronts in some cities and the destitution in others, what I have in mind is an intervention that is visible at the scale of satellite imagery. When seen from space, all cities seem to be shaped by water systems. Granted, there are some exceptions, but even the form of a desert city, like Riyadh in Saudi Arabia, is significantly shaped by the Riyadh river landscape that connects to the Wahdi Hannifah. Indeed, most large cities in the world had their origins in a river landscape like Cairo, Paris, London or Beijing. In a related category are those cities that are situated on river branches that form a large delta like Calcutta, New York or the cities of the Randstad. Equally numerous are cities that originated as harbours, like Mumbai, Jakarta or Chicago. Cities around a large bay, subject to tides like Tokyo, Lagos or Sydney belong to a fourth category. Finally there is a small group of cities that stretch out along the shores of an ocean straight like Victoria Harbour in Hong Kong, the Bosporus or the Øresund.


The relevance of water

The original water systems of cities are sometimes severely challenged by growing settlement patterns. In some cases, like in Mexico City or Los Angeles, only remnants of the water system can be traced. But in many river cities, including Los Angeles, Paris, London, Milan and Calcutta there is a renewed interest in transforming the land along riverfronts that has become newly available due to industrial closures. The goal is not to repair the original water systems to their natural conditions, as that would not be possible, but to use such recently vacated land in a manner that repairs the natural forces of the river, and sometimes even makes room for periodic flooding, like along the Waal River just outside of Rotterdam. Or in the case of Riyadh, where the ground water that is pumped up to provide the city’s water supply is treated and, as grey water, redirected back into an otherwise mostly dry riverbed. The same type of repair takes place in harbour cities and bay cities. Tokyo has large tracts of land around the bay under regeneration.


The observation that most urban agglomerations were shaped by their water systems instils optimism, because a better un-derstanding of the natural systems that existed and that were altered can inform the design of new cultural landscapes, land-scapes that can be designated as commons for a large metropolitan area. Such commons could improve the urban ecology of city regions as well as their social conditions. At the same time, the correlation between water systems and urban form is also a deadly serious matter. Some of the fastest growing urban concentrations, among the world’s most populated cities, are situated barely above sea level. They are located in the flood-planes or deltas of large rivers and must depend on levees for protection from flooding.



The second important observation when looking at a scale comparison of the world’s largest cities is related to density, a concept design professionals claim to understand, but rarely fully grasp. It taxes our common sense to imagine how Calcutta with its al-most eighteen million people could fit into the surface area of the city of San Francisco plus the county to its south, San Mateo, where altogether one million people live. Imagine that a space occupied by one person in San Francisco would need to be shared with seventeen additional others. People in many Asian cities live at such densities, and many additional millions will live under such conditions in the future.


A city designer’s chief contribution to city transformation is setting the dimensions of streets and lanes, block and parcels, building setbacks, entrances and driveways, building heights, the separation between buildings and the size of building footprints. The result of these decisions determines the scale of a city. These decisions also determine human experience of space: the length of a walk, the likelihood of human encounter, the amount of light that is received, protection from wind, exposure to noise, what is available to our eyes, when we feel intimacy, when we are participants on a civic stage. In short, city scale determines all aspects of human experience including the energy needed to transport us and the energy needed to heat or cool dwellings and commercial places.


In comparing the scale of cities we reflect on the dimensions of the elements in the urban fabric, and how these elements re-late to human experience. Everyone with a recently built computer can connect to a well-known global map server and slowly fly across cities. We have done just that to create a transect through a recently built suburban subdivision of the San Francisco Bay Area. Transects are known in biogeography as a sampling method with reduced dimensionality; three frames are reproduced here along such a transect.


The top picture shows an office park on the eastern edge of the San Francisco Bay Area that emerged in the 1980s when large corporations started to move out of downtown San Francisco to office park settings. The next frame, a mile further to the east shows where the employees of the office’s campus are intended to live. The third frame, another mile further east, shows the con-tinuation of the same neighbourhood with a high school.


Like so many times before in history, former agricultural land has turned into a landscape of capital. Units of home and office space production have generated the form of the subdivision. Different, but typical of recently built subdivisions are the land de-velopment standards; mandatory dimensions have grown to ever larger scales of production. Starting with large earth moving machines, areas were graded to hold upwards of 400 homes of very similar design. Each home fills its parcel without leaving much space for a yard or garden. The width of the roads inside the neighbourhood is strikingly wide at 20m , as half the width would be wide enough for the number of cars that will travel on them. The arterial streets are even wider; designed as limited access roads, some residents might have the backs of their homes face such arterial streets, but have their address on the local street that runs parallel to the arterial street. The right of way measures 83m in width, which is just a little wider than the Champ Elysées in Paris. Notice that the left turn lanes, two of them right next to each other, are about 150m long. However, the connec-tivity of the street grid is very poor; only two streets generally connect out of a neighbourhood and onto an arterial.


The generous dimensions add up, generating great distances between places where people need to be. Extrapolated to the metropolitan scale, reducing such dimensions could save much space and energy. As a result, residents would not entirely de-pend on their automobiles. In the neighbourhoods shown, the automobile is a necessity even for short trips to take a child to the home of a friend or to the ball field, or an elderly person to the shopping centre.

What will happen 30 years from now? Will it be possible to transform the subdivision shown here–like so many others–to use the space more economically, more efficiently with changing demographics in mind? Different from the urban renewals of the in-ner city in the 1960s, the needed transformation would not as much address the reuse of private properties, as private properties are intensely used; the renewal would have to deal first of all with all the land that the developers have deeded back to cities and counties, the roads and open space that became a by-product of the large scale grading at the beginning of the land development process. The conclusion to be drawn for the present is that the permitting authorities should insist on shrinking space standards. Space is a resource, just like water, energy, access to public transportation and so much else. City design remains a political, social and environmental affair.


Urban history cannot be explained without reflecting on the inertia that exists in city transformations. The demographic trends, environmental crisis and problems with social health and wealth have been identified for many decades, and collectively we know the coming decade will need to be decisive, because of the significant increases we can expect in urban populations and our competing need to live within the means of our diminishing resources. Of course, the same could have been said at more or less regular intervals throughout urban history, but that is the point. Urban history is again in such a decisive period. To direct, or at least influence the current urban transformations we need to evaluate what has influenced our professional practices and what knowledge is needed to direct urban transformation in the future.


Peter Bosselmann is a Professor of Urban Design at the University of California, at Berkeley. His most recent book, Urban Transformation – Understanding City De-sign and Form was published by Island Press, Washington DC in 2008
 The maps reproduced here are part of a larger map collection that appears in the book. They are reprinted with permission by the author and publisher

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