Suburbia Project

Growing Sustainable Suburbs: An Incremental Strategy for Reconstructing Sprawl

Rather than seeking massive top-down reconstruction projects (which have so often failed in the past anyway) the authors recommend piecemeal changes.

By Lucien Steil, Nikos A. Salingaros, and Michael W. Mehaffy
Published April 09, 2006

[Editor's Note: This essay is an excerpt from a longer paper that will appear as a Chapter in the book New Urbanism & Beyond: Contemporary and Future Trends in Urban Design (Tigran Haas, Editor), due to be published in 2007.]

Introduction: Re-integrating the Urban Form

A new way of understanding the growth of urban form leads to practical suggestions for reconstructing a more sustainable suburbia. Combining theoretical results with pragmatic experience, and combining "top-down" controls with "bottom-up" processes, we offer guidelines for implementing small-scale changes that eventually lead to large-scale improvements.

The goal is a re-integration of the urban realm, resulting in a more humane and sustainable environment. Importantly, this can be achieved by a minimum of new investment applied all at once. Changes need to be implemented over time, and subsequent interventions will respond to the success of the preceding ones.

Suburbia Predates Modern Cities

Although attention tends to focus exclusively on the particular modern phenomenon called "sprawl", we must recognize that suburban expansion has existed since the beginning of cities. A city, whether planned or haphazard in its initial form, tends to grow organically as its population increases. Legal measures to check the possible overgrowth of the central urban fabric and divert new growth to the urban periphery go back to the beginnings of civilization.

In its earliest form, a relatively sympathetic exurbia maintained strong organic and structural ties to the city. Outer growth often completed some of the insufficient functional and spatial requirements of the tightly-delimited historic city areas enclosed by natural or man-made barriers. Military and religious uses, for example, needed large open and flexible development spaces. Markets and business activities often found the ancient cities too restrictive for their activities.

These various activities and uses attracted a variety of other heterogeneous activities serving and supporting monasteries, cattle markets and fairs, military barracks, stores, travelers' inns and hostels, and later manufacturing and industrial installations. Houses, shops, restaurants, bars, and various services contributed to create suburbs with qualities similar to those one could find in the central cities.

These benign suburbs conceived and built as mini-cities most often respected the scale, connectivity, hierarchies, and proportions found in the best urban centers, and they had a symbiotic complementarity with the cities they gathered around or grew out from. They respected pedestrian-scale principles, with the result that they were walkable urban extensions characterized by relatively flexible, organic and vital urban structure. In today's terms, they were sustainable urban morphologies.

Since that time, suburbia has variously been associated with ideas of liberation, freedom of choice, autonomy, connection to nature, space and health, priority of family over society, individual emancipation over collective regimentation, private integrity over public alienation, and many more worthy goals.

On closer examination, however, the connection is more imagined than real. In any case, the appeal of modern suburbia is undeniably strong. Hardly anyone has been really obliged to move to the suburbs, but clearly many millions have elected to do so, for these and perhaps other reasons (notably economic factors; particularly land prices).

The City as Network

Many authors have proposed reasonable and incremental changes for urban and suburban morphology, but implementation has been haphazard and largely unsuccessful. The reason is that urban morphology is the result of deeper generative processes, which must also be changed.

The configuration of buildings is driven by the physical communications network: the street pattern and infrastructure such as the networks for sewage utilities that are normally buried underground. The networks determine to a large extent how the visible, aboveground built structure is configured, and that is not going to change until the geometry of the network changes.

The network, in turn, is determined by current social, political, and industrial practices in transportation and energy use and availability. Building a subway to connect low-density sprawl makes little economic sense if the transportation patterns generating sprawl remain in place; such a high-capacity heavy rail system should be reserved for a medium-to-high density city.

Dynamic processes drive a city to function as a network, and it is essential to grasp them. A new understanding comes as a result of the recent application of scientific methods to urban structure, which are not generally known to the majority of practitioners. Key concepts and results were developed by the authors and our friends.

We have drawn on morphogenesis, as developed in biology, and on the science of networks. Christopher Alexander has shown how complex form is coherent or not, depending upon the process by which it evolves, and this relies on the sequence of steps that are allowed (Alexander, 2004).

An Incremental Urban Strategy

Healthy urban evolution can thus be guided by a relatively simple set of codes. Conversely, the wrong codes will grow a monster, regardless of the measures taken later to impose a particular form. Such changes, we believe, can be made in piecemeal fashion, much as living organisms grow new blood vessels to organs as those develop. This will require a different management approach, and a radically different urban strategy.

The network model of cities reveals that urban forces are very different from the physical form that we usually see. Every piece of healthy urban fabric is characterized by a coherent, robust network structure. The properties that make it robust are precisely those that minimize network breakdown from random cuts (studied extensively by the US military in reference to the Internet and the electronic communications networks).

Our method is to identify the urban network, then to channel its growth so as to make it as robust as possible. Then, any perturbation is much less likely to lead to a catastrophic collapse. Our results translated into physical form lead us to propose a geometrically complex urban fabric, which is inhomogeneous and extensively connected. We can only provide the barest outline here of what is an entirely new understanding of urban structure.

We need to acknowledge the sheer size of suburban real estate and recognize that to reform its shortcomings is a hugely massive task. This vast structure, accommodating over half of all urban dwellers in the USA and Europe, was not created overnight - and its repair will not occur overnight.

Piecemeal Changes

Rather than seeking massive top-down reconstruction projects (which have so often failed in the past anyway) we suggest that a more powerful and more effective strategy is to make piecemeal changes. These are to be effected both in physical projects and in what may be called the suburban "operating system": i.e., the system of codes, regulations, and economic incentives.

It is this legislated code structure that produced suburban morphology in the first place. We must provide tools that exploit small points of incremental change, which serve to re-connect the present fragmented structure into a more coherent, more functional urban system. Like gardeners planting seeds, and pruning or weeding a bit here and there, we must seek to induce organic processes of regeneration and reconstruction.

Following is a more detailed proposal of how to achieve such an incremental process of transformation. All of these suggestions need to be initiated by an immediate change in the zoning and construction codes, so our first task is a legislative one, not an architectural or urban one.

Cognizant of the immense difficulties of changing codes, we have devoted the final section of this paper to this problem. These necessary changes are not necessarily in order of implementation, as a number of these changes must be done in tandem, or in a back-and-forth iteration.

Preserve Suburban Benefits

The evidence already shows that the modern suburb in its current disintegrated form (sprawl) is not a sustainable form of development, and needs to be reformed. This problem is particularly important as the developing world looks to the developed world for leadership in its own new, unavoidable suburban development.

But this reform need not take away the characteristics that drove suburban expansion in the first place: a greener and more rural livable environment, access to larger homes on larger properties, use of the automobile as an option (and not as a necessity), and so on.

Instead, reform needs to be aimed at creating a richer and more connected structure, allowing alternative modes of transport, greater ranges and locations for activities, and greater coverage of property. In this sense, the reforms presented here are less about limiting choice, and more about expanding choice and diversity.

Along with these reforms must go a reform in our thinking about cities, and what Jane Jacobs termed "the kind of problem a city is". We must cease to assume that changes can only happen with massive, expensive, "top-down" solutions.

Indeed, we do not believe that a massive, top-down approach will even succeed in addressing the connective failures of modern suburbia, assuming that one was even feasible in this age of growing pressure on public revenues. Rather, a new kind of strategic and iterative mix of top-down and bottom-up approaches will be necessary.

Reform the Operating System

Strategic reform of the "operating system" that generates suburbia will result in emerging changes in the existing structure. Relatively small economic management tools, such as shifts in tax policy, can be powerful bottom-up tools. (One powerful economic change may already be happening: a drastic escalation in energy costs, which may well trigger major suburban reconstruction.) Relatively small pilot projects and incremental connective elements can act as catalysts for more growth.

To be sure, some top-down tools are useful, if carefully applied. Occasionally, new infrastructure can be a very useful intervention -- new light rail lines, for example. We value the lessons provided by the best urban reconstructions of the past, including Haussmann's transformations of Paris, Burnham's work in Chicago, and others.

Key changes were made in strategic areas, while large areas between them were kept mostly intact. Those successful approaches were highly selective: changing a minimum of the geometry to make a maximum of difference to the functioning of the whole.

We need also to keep in mind what can go horribly wrong with a heavy-handed top-down approach. Unfortunately the utopian architect Le Corbusier offers us perhaps the most cautionary tale here, as his legacy was implemented disastrously in many cities, including New York under Robert Moses, and Algiers under the post-war French colonial government. (Thankfully, Le Corbusier's horrific Voisin Plan for Paris was not implemented, although the suburbs of Paris were built in this image, and their recent eruption in riots cannot entirely be dissociated from their urban form).

The Power of Emergent Processes

All of these lessons remind us of the power of change over time - the power of emergent processes, and "game theory" dynamics - and the need to make interventions very carefully, intelligently and sensitively. We believe this can be accomplished with a new toolbox of the sort outlined here.

Much more work needs to be done to develop detailed strategies for such tools in varying contexts, and to document their likely results. However, we do believe that with such an improved understanding, we can act on a complex system like a contemporary suburb and, with the right diagnosis, in effect, heal it, much like a doctor heals a sick patient without major surgery.

Or to return to the gardening metaphor, it may not be necessary or even desirable to clear the old weedy garden; we may find that a bit of pruning and weeding, and a few seeds strategically planted, can, with a bit of time, produce a very nice garden indeed.


Lucien Steil, Nikos A. Salingaros, and Michael W. Mehaffy are the President, Vice-President, and Secretary, respectively, of Katarxis Urban Workshops. Visit the website: Nikos A. Salingaros is also a Professor in the Department of Applied Mathematics, University of Texas at San Antonio. Visit his website:


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