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Exploring The Relationship Between Urban Morphology And Resilience In A Few Neighbourhoods In Pretoria. Darren Nel & Karina Landman University of Pretoria. Contents. Introduction Resilience and urban form Comparison of four neighbourhoods The evolution of the suburban tree

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Exploring The Relationship Between Urban Morphology And Resilience In A Few Neighbourhoods In Pretoria

Darren Nel & Karina Landman

University of Pretoria

contents
Contents
  • Introduction
  • Resilience and urban form
  • Comparison of four neighbourhoods
  • The evolution of the suburban tree
  • Conclusion
introduction
Introduction
  • Recent studies in urban planning highlighted importance of urban resilience
  • Of these – few starting to show relevance of urban morphology for resilience
    • Attributes & indicators
    • Also linked to typical structure: tree or leaf
    • Paving way for new ways to study urban phenomena
urban resilience
Urban Resilience
  • Amount of change system can experience without collapse or total transformation
  • Specific sub-systems more vulnerable to such changes due to disturbances
    • Maybe because it is still recovering from disturbances or shocks
  • Important to understand pattern of disturbances and ability of urban system to deal with these to strengthen resilience
resilience and urban form
Resilience and urban form
  • “Urban resilience can be understood as the robustness of urban structures and networks against random failures” (Salat 2012)
  • Failures: small scale (disruption in local transport networks or energy supply) or large scale
  • Influenced by urban form
lattice tree or semi lattice
Lattice (tree) or semi-lattice
  • Alexander (1965): Cities may reflect lattice (no overlaps) or semi-lattice (overlaps)

City should not be a tree –

Need to allow for social & spatial overlaps

tree or a leaf
Tree or a leaf
  • Salat (2011): 2 paradigms
    • TREE: Disconnected and closed (travel far)
    • LEAF: Connected on intermediate scales

More resilient:

Fractal structure

Multi-connected

Complex on all scales

resilience and urban form1
Resilience and urban form
  • Histories of cities have evolved from leaf-like structures to tree-like structures with consequent loss of efficiency and resilience

(Salat 2011)

change over time
Change over time

(Salat 2011)

indicators
Indicators

CONNECTIVITY

INTENSITY

COMPLEXITY

PROXIMITY

DIVERSITY

complexity
Complexity
  • Quality environments: complex, diverse & with overlap
  • Due to incremental change and adaptation over time
  • Essential for resilient city:
    • Rich urban fabric through multiple points of contact, engage & interface
    • Link to connectivity & diversity

(Salat 2011)

connectivity
Connectivity
  • In historical city it grew, in Modern City over-simplification reduced connectivity
  • Understood through role of streets & intersections
  • Need high connectivity, mechanisms to create new connections & low control
  • Thus adaptive capacity critical – ability for self-organisation

Le Havre (Salat 2011)

diversity
Diversity
  • Complexity & adaptive capacity enhanced through diversity
  • Among similar objects at same scale
    • E.g. population groups, income groups, housing units
  • Or objects at different scales
    • E.g. metropolitan facilities or landmarks in selective areas
  • Increased diversity also allows for greater redundancy and thus ability to cope with disturbances
proximity
Proximity
  • Diversity also linked to proximity
  • Average distance between two things
    • E.g. home & leisure / home & work
  • Aim – minimum distance to reduce travel needs and related costs & energy
intensity density
Intensity (density)
  • Biggest opportunity for generation of urban opportunity through intense interactions & high levels of population support
  • Link to complexity & diversity
  • Concentration of object in given area
  • -E.g. people or housing
measurements 3
Measurements (3)
  • Connectivity
    • Nodes (Intersections)
    • Connections
    • Distance between intersections
    • Cyclomatic complexity
selected study areas older areas
Selected study areas: older areas

Typical older ‘open’ neighbourhood

Typical older neighbourhood, BUT closed-off

analysis of two older neighbourhoods
Analysis of two older neighbourhoods
  • Typical older neighbourhood in Brooklyn
    • Grid pattern
  • Typical older neighbourhood
    • Internally: grid pattern
    • BUT closed-off
selected study areas gated areas
Selected study areas: gated areas

Security Estate

Enclosed Neighbourhood

analysis of two types of gated communities
Analysis of two types of gated communities
  • Enclosed neighbourhood
    • Existing area closed off for security purposes
  • Security estate
    • Private development
the evolution of the suburban tree3
The evolution of the suburban tree

A

B

C

D

E

Should a gated community be considered as a new type of urban morphology or just the ultimate manifestation of suburbia?

Adapted from Salat (2012)

the evolution of the suburban tree4
The evolution of the suburban tree

Evolution of modernistic planning In Tshwane

the evolution of the suburban tree5
The evolution of the suburban tree

Evolution of modernistic planning In Tshwane

conclusion 1
Conclusion (1)
  • Gated communities represent an evolution of modern town planning principles
  • Can be considered as the ultimate representation of suburbia with a wall
  • In terms of morphology and function – very different from typical Medieval towns that were complex and well connected
conclusion 2
Conclusion (2)
  • Suburbia & typical gated communities can be well connected internally but disconnected with the larger urban fabric.
  • Therefore it tends to follow a typical tree-like structure
  • However, a city is/should not be a tree
    • As a tree is not resilient
    • Tree-like structures did not perform well in terms of indicators for resilience
    • Therefore, based on morphology, suburbia and the typical gated community is not likely to be very resilient
  • Need a city of leaves to enhance resilience
    • To accommodate complexity, connectivity, diversity, proximity & intensity