THE ROLE OF URBAN COMPLEXITY IN THE PRACTICE OF URBANISM

Emergent Urbanism

Mathieu HélieTranslated from the original

French

Urban complexity theories

Since the 1990’s, many complexity science programs have researched urban complexity.

Pierre Frankhauser

French geographer Pierre Frankhauser studies the geometry of urban areas to determine their fractal dimension.

Bill Hillier

A spatial configuration theory, Space Syntax predicts the probability of traffic in the urban network, and some land uses

Michael Batty

Cities and Complexity is the biggest treatise specifically on complexity science applied to cities. (Cellular automata, agent-based models, mathematical equations, etc.)

No conclusion. The author admits that it is only an exploration.

Nikos Salingaros

Urban web theory, a physical connection network

Definition of a fractal city

What’s it for?

Up to now no theory attempts to explain how or why cities are complex and/or emergent.

No link to the process of urbanization.« We want to know how to do our job »

History of urbanism

Solutions to scale problems that appear whenever the city grows larger

Organic urbanisation

The collapse of the Roman Empire ends the first attempt at urban planning

For the next 1000 years urbanization is a random unconscious process

Cities grow « organic » morphology

Characteristics of organic urbanization

Land is built up as the economy necessitates

Economic conditions change too slowly for change to be noticeable

No interventions other than a code limiting new construction

Organic urbanization still exists!

Where no planning system is enforced organic urbanization procedes naturally.

Pre-industrial planning

In the 17th century some towns reach hundreds of thousands of inhabitants

The organic network becomes jammed

Urban planning is (re)invented

Examples

The grid

New law codes regulate property division to maintain a uniform grid for traffic circulation.

Usage zoning is not adopted yet

Code of the Americas, New York, Torino, Barcelona

New York

Multiple grids collide into each other until the Plan of 1811 settles the entire island

The metropolitan scale

The regular grid is impossible to navigate with hundreds of streets

Cities routinely reach a million inhabitants

Transportation systems multiply and clash with each other

Architects provide the answer

The modern city will be a utopia planned with industrial science to build the city of the machine civilization.

The city is designed at the scale of millions of inhabitants

Characteristics of urban planning

The network is planned as well as the land uses through architectural building plans and zoning codes.

City plans become architectural designs

Scale problems of urban planning

Cities sprawl outSocial, economic and

ecological problemsHow can we make

sustainable cities?

Evolution of urbanization processes

As we progressed to modernity the process of urbanization became less spontaneous and more industrial.

How did this impact urban complexity?

General theory of complexity

Stephen Wolfram, A New Kind of Science

Christopher Alexander, The Nature of Order

The Wolfram method

Observing nature allows us to formulate theories of natural laws

We have to guess these laws and test them with experiments

Observing the computational universe allows us to know the precise laws exactly

Wolfram’s classes of phenomena

Type I: deadType II: linear or regularType III: fractal hierarchicalType IV: fractal random

Type II urbanization

Type III urbanization

Type IV urbanization

Alexander

Emergent processes are the key to natural or « organic » morphology

“I believe that the whole idea about the natural environment has been turned on its head actually in a very strange way.  For about a quarter of a century, people have been in effect obsessed with saving the environment - which is of course a very sensible thing to do when it's being ravaged and destroyed.  But the real problem is that we won't be OK, in terms of building or in terms of nature or anything else, until we learn how to make nature.”

Morphogenesis

The form of a living system is the result of the reiterating local actions of elements following shared geometric rules. (DNA, physical law, computer programs)

Emergence of urban order

A single geometric rule regulates the growth of random buildings

Morphogenetic urbanization

Dividing and subdividing land into a city works on the same principles as natural cell division

The complexity of the urban system depends on the number of actors in its production

Actors reuse the same geometric rule when growing the environment

Comparison to modern planning

The plan sets up a scale for the cityThe developer decides the size of lotsThe builder imports building plans from whereverInhabitants decide nothing at all

Result:

Emergent urbanism

Rethink the role of the homeowner in house buildingRethink the role of the developer in subdivisionRethink the role of public works in the networkRethink movement entirely

Shape grammars

Sell a building system instead of a building plan

Subdivision

Lots are drawn and selected on the fly instead of being subdivided in advance

The complex grid: village

The complex grid: town

The complex grid: city

Shared Space

De-signalize public space

Replace control with negotiation

Obstacles

Planning regulationsThe permitting systemThe banking and financial systemPolitical habit

Fractal government

Government is affected by scale problems when the metropolitan scale is reached

Merging contiguous communities is not always a viable solution

Fractal scaling provides an interesting template

Paris-Métropole

Conclusion

Complexity means solving problems at every scale

Emergent geometric rules are necessary to create complex cities

Each aspect of the urban development process must be redesigned

Thank you

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Copyright Mathieu Hélie 2010