Darren Nel & Karina Landman University of Pretoria

1. Exploring The Relationship Between Urban Morphology And Resilience In A Few Neighbourhoods In Pretoria Darren Nel & Karina Landman University of Pretoria

2. Contents • Introduction • Resilience and urban form • Comparison of four neighbourhoods • The evolution of the suburban tree • Conclusion

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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)

9. Change over time (Salat 2011)

10. Indicators CONNECTIVITY INTENSITY COMPLEXITY PROXIMITY DIVERSITY

11. 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)

12. 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)

13. 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

14. 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

15. 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

16. Indicators

17. Measurements

18. Measurements (2)

19. Measurements (3) • Connectivity • Nodes (Intersections) • Connections • Distance between intersections • Cyclomatic complexity

20. Selected study areas: older areas Typical older ‘open’ neighbourhood Typical older neighbourhood, BUT closed-off

21. Analysis of two older neighbourhoods • Typical older neighbourhood in Brooklyn • Grid pattern • Typical older neighbourhood • Internally: grid pattern • BUT closed-off

22. Case 1: Brooklyn

23. Brooklyn: unit of analysis(800 x 800 m blocks)

24. Brooklyn; Proximity

25. Does not lend itself to large enclosures

26. Case 2: Irene

27. Irene: unit of analysis (800 x 800 m blocks)

28. Irene: Proximity

29. Selected area of concentration

30. Concentration of different types

31. Concentration of different types

32. Selected study areas: gated areas Security Estate Enclosed Neighbourhood

33. Analysis of two types of gated communities • Enclosed neighbourhood • Existing area closed off for security purposes • Security estate • Private development

34. Case 3: Newlands

35. Case 3: Newlands (enclosed area)

36. Newlands: Unit of analysis (800 x 800m block)

37. Newlands: Proximity

38. Most of Pretoria east: suburban layout

39. Case 4: Silver Lakes

40. Silver Lakes: unit of analysis (800 x 800 m block)

41. Silver Lakes: Proximity

42. The evolution of the suburban tree

43. The evolution of the suburban tree A B C D Salat (2012)

44. The evolution of the suburban tree A B C D Salat (2012)

45. 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)

46. The evolution of the suburban tree Evolution of modernistic planning In Tshwane

47. The evolution of the suburban tree Evolution of modernistic planning In Tshwane

48. 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

49. 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

50. Questions?