Transcript Is London’s Intensifying Urban Structure Creating a More Sustainable City? Duncan Smith 15

Is London’s Intensifying Urban Structure
Creating a More Sustainable City?
Duncan Smith
15rd October 2008.
Urban Form, Function and Accessibility: an analysis of London’s
Intensifying Urban Structure using 3D GIS
Why does Urban Form Matter?
Monocentric and polycentric cities discussion.
Integrating Geography and GeometryApproaches to measuring urban form and function.
Density, Accessibility and Urban
DevelopmentIs London’s intensifying urban form creating a more
sustainable city?
Why Does Urban Form Matter?
Defining Urban Form
“All physical aspects of the city, its buildings, streets, and all other elements that
make up the urban realm” (Talen, 2003).
A “diagram of forces”
(Darcy Thompson, 1917)
Embedded in Processes Shaping Cities
Built environment reflection of forces that shape cities; container where all urban
activities take place and a major influence on future urban developments.
Geographical research engaging with urban form– Economic geography: structural economic change/globalisation,
urban development.
– Social/cultural geography: housing and social segregation,
gentrification, access to services, urban quality of life.
– Urban policy and planning.
– Urban Sustainability: energy use in buildings and transportation.
All aspects interlinked and cannot be understood in isolation
Urban Form and Sustainability
Urban Form Explain Travel Patterns?
Influential research by Newman and Kenworthy (1989).
Argument from Compact City theory- high density mixed use city
minimises trip lengths, encourages benign modes. Car several times
less energy and space efficient than public and active transport.
Compact City Criticisms
– Not geared to process- Urban form evolves with the economy, transportation
technology, socio-cultural trends and planning policy. intensification policies
not achieving behaviour change.
– Loosely defined- how high-density and mixed-use? What about variation
within cities?
– Ignoring economic realities of 21st century cities- polycentric growth.
Happening even in European cities.
Debates in Urban Form and Sustainability Research
Short term costs (e.g. fuel taxes) more significant influence on
travel behaviour than urban form (Breheny et al, 1998) but...
Long Term Importance
Built environment massive fixed capital investment, path
dependence. Affects costs and viability of different transport
modes for decades, even centuries.
Future Energy Costs and Climate Change
Cheap energy era likely ending. Inefficient cities ‘rustbelt’ of
21st century? Currently unprecedented urbanisation and
climate change risk.
More impetus than ever to improve urban sustainability. Need
better understanding of relationships between urban form and
socio-economic processes.
Monocentric and Polycentric Cities
Traditional Monocentric City
High density urban core where accessibility greatest and
agglomeration benefits maximised. Radial dense nature
encourages public transport.
Specialisation / Diversity Tension
Arguments that high density core creates mix of uses
(Jacobs, Alexander); and conversely that central
agglomerations push out lowest value uses (Alonso).
Monocentric Inefficiencies?
Long distance tidal commuting patterns with live/work
divisions, congestion, lack of land.
Post-Industrial Push and Pull Forces
Widespread automobile ownership creates potential for
agglomerations in off-centre locations- cheaper land, less
congestion. Currently cities simultaneously affected by
forces of concentration and dispersion.
Globalisation and
Information economy;
gentrification,
cultural/retail/tourism
synergy.
Residential dispersion,
manufacturing, large
scale retail/leisure.
Consensus on Sustainable City Form?
‘Dispersed Concentration’
Framework
High-density mixed-use ideas revised for
hierarchical network of centres. Fractal structure
incorporates agglomerations at multiple scales.
Greater potential for live/work relationships in
sub-centres.
Classical Theory
Proposal has similarities to historic Garden City
ideas and Central Place theory, though applied
at intra-urban (not inter-urban) scales.
Questions
Empirical evidence? Relationship with
agglomeration economies for different
industries? Peripheral centres car based? Livework relationships at different scales?
Urban Task Force Key Diagram (1999)
Local Scale Urban Form
Local scale cannot be overlooked. Relevance to
sustainability issues, and to empirical measures of
urban form.
Sustainability Issues at Local Scale
Density planning without considering built form
likely to fail (Sherlock, 1996). Permeability, street
network.
Quality of life factors- urban vitality vs. town
cramming. Balance between density and liveability.
Urban Development
Local scale where urban change occurs. Economic
factors driving urban development can be
considered with property and planning permission
data.
‘Creative destruction’- speculative development
dominates property industry, driving growth
(sustainability costs are externality).
Example of City of London transformed during
boom (Batty, 2005).
Relevance for London
Rapid Expansion of London
Massive employment growth, and immigration led
population growth. (Crash implications!?).
Planning Policy in London
Recent policy based around central growth model,
enhanced radial transport. Most sustainable approach
or could dispersal have benefits?
Conclusions
Unresolved debate in monocentric and polycentric city
forms. Need for better data and analysis of urban form
at multiple scales, linked to socio-economic urban
processes and development.
Incorporating Urban Form: Geography and Geometry
Aggregate Methods in Urban Geography
Powerful for larger scale city-wide phenomena. Compliments socioeconomic data.
Problems with MAUP and handling finer scale data such as urban form.
Typically measured indirectly e.g. population density.
Approaches to Measuring Urban Form
Geometrical methods in architecture, planning and morphology.
Restricted in scope due to high data volume and complexity.
Increasingly data and computing power available for geometrical
analysis of whole city (Batty, 2001). Methodologies still in development.
Geographies to Incorporate Urban Form
–
–
–
Remotely sensed city (Longley, 2002), detailed physical
representation.
Address geography, linked to function and property data at
building premise level.
Network geography, accessibility at street and pedestrian
level.
Data Models for Integrating Between Scales
Methodologies?
Amazing range of new data. Need methods to integrate fine
scale data, and aggregate at multiple scales respecting
urban form. New geographical approaches emerging.
Address Matching at Fine Scale
Spatial address infrastructure greatly improved (OS AL2).
Unit postcode links straightforward, then individual address
possible.
Block Based Aggregation
Buildings between streets.
Street Based Aggregation
Streets themselves are units used.
Larger Scale Grid
City wide representation, try to avoid MAUP problems with
zones (but may need to join to zones).
Density Analysis- Centres of Activity
Economic activity in particular urban areas with
distinct density and accessibility patterns.
Urban Activity Centres Typology
Traditional monocentric and more recent polycentric
trends overlapping in world cities (Hall, 2003):
–
Central Business Area
–
Expanded Central Business Area
–
Tertiary Business Developments
–
Outer Centres
–
Edge City Developments
Testing Theory with Data
Use urban form/function database to test theory,
quantify in London context, define relationships
between density and accessibility.
Density and Valuation Office Data
Great Potential
Address based data of
commercial property
including detailed function
and floorspace. Fixed at
2005.
Rateable Value Issues
Calculated as floorspace
multiplied by use factor
(office generally higher) and
a smaller rent related factor.
Possible to work backwards
to separate values, but
complicated and not yet
complete.
Useful Proxy of
Employment?
Good fit for office
employment, but variation at
lower densities. Likely
caused by lack of calibration
for other employment e.g.
industrial, retail.
Office Density Analysis
Monocentric
Dominance of central
agglomeration, merging
into inner city.
Tertiary Centres
Canary Wharf.
Hammersmith?
Outer Centres
Much lower density,
various scales. Largest
Croydon, Kingston,
Uxbridge.
Edge City
Difficult to identify here.
Need mix of uses and
travel.
Inner City
Distinctive inner city area at
medium density. Leading
into Western corridor
highlights West/East split.
Change over time?
Recent change reinforcing
central dominance.
Retail and Local Services Density Analysis
Smaller Scale
Agglomeration
Retail and services
functions in more
dispersed network.
Linear streets visible
in retail patterns.
‘City of Villages’
Whilst office very
monocentric, retail and
services in polycentric
network at range of
scales.
Mixed Use
Visualisations
Possible to combine
functions to visualise
mix of uses. Here
office (blue) combined
with retail (yellow).
Accessibility
Descriptive analysis so far. Can we try to explain
current urban form patterns?
Public Transport Accessibility
Major influence on activity centres in London,
both historic and current growth.
Potential Measures
Measure how much is accessible within a certain
cost e.g. population accessible within 45 minute
public transport journey.
Fine Scale Accessibility
Network analysis of local street network, can
consider more pedestrian focussed and cognitive
representations of city.
Potential Accessibility and Travel
Behaviour
Important to consider relationships between
potential accessibility and actual travel behaviour.
Density and Accessibility
Density and Accessibility Conclusions
Expansion Policy in London
This analysis agrees with current policy that highest density employment
achieved at highest accessibility levels, and Inner City greatest potential for
expansion.
Outer London Unsustainable Patterns?
Outer London centres achieving better than expected density given access
levels. This due to car access or more local travel? Back to Monocentric and
Polycentric discussion.
Need actual travel data to categorise trends in Outer London and distinguish
between Outer Centres and Edge City developments.
Travel and Sustainability- Distance and Mode
Greater car use to suburban
employment destinations, so often
described as less sustainable.
Distance and Mode
Efficiencies
This analysis ignores distance
travelled and energy used in
public transport journeys.
Walking
and
Cycling!
Travel and Sustainability- Outer London Diversity
Possible to calculate average
carbon per journey, using distance
and mode data.
Edge City
No longer centre-suburbs split, but
edge city vs. rest split. Car
dominated office parks by far least
sustainable.
Suburbs Most Sustainable?
Closer live-work relationships and
more active transport. Central
London public transport dominated
but long distance.
Outer Diversity
High variation in Outer Centres, and
simple central-suburbs divisions
inaccurate.
Missing Economic Specialisation
People travelling further to centre
for more specialised productive
jobs. Should be considered.
Economic Specialisation and Sustainability
Economic Specialisation
Proxy
Use census data on employment
categories. Sum the top three
categories for proxy.
Outer London Mix
Most Outer Centres lower
productivity jobs. Many Edge City
high productivity, not back office.
Specialisation and sustainability
tension.
Combine Economic
Specialisation and
Sustainability
Best combination in West London
centres. East fares much worse.
Market favoured West, why? Image
and closer to workforce? Also local
scale factors?
Conclusions of City Wide Analysis
Monocentric, but Polycentric Trends
Historic centre dominant and expanding, but diverse polycentric trends
at fringes. Centre combines very high economic specialisation with
reasonably sustainable travel.
Outer London Contrasts
Outer London includes least sustainable (but productive) edge-city
developments, along with most sustainable town centres with high livework integration. Many outer centres lagging in productivity.
Support London Plan approach?
Central agglomeration focus balancing economic and relative
sustainability. Questions of intensification impacts at local scale.
Polycentric Issues
Notable car based edge city trends in West. Outer town centres high
sustainability but mixed economic success. Could potentially expand
role in employment, but need to overcome market bias.
Town centre failures in East London agree with plan’s regeneration
focus.
Integrating Local Scale Analysis
Focus of the research is integrating city wide trends
with changes at local scale.
Questions for Local Scale Analysis
Are local urban form issues contributing to the highly
variable economic and sustainability trends in Outer
London centres?
How is intensification in Central and Inner London
impacting urban texture, mix of uses and live-work
relationships?
Currently Analysis Not Complete
Research at local scale ongoing.
Intensification and Mega-Development
Opportunity Areas
Low density and high access levels, priorities
for expansion.
Brownfield railway and docklands, British
Waterways/railway companies acting as land
developers.
Block Level Visualisation
Explore density data related to Opportunity
Areas (shown as transparent blocks). Block
level good intermediate geography, represent
urban texture.
Analysis of Mega-urban
development
New scale of property investment transforming
locations. Private sector led master-planning
at extreme densities, often isolated from
surrounding urban fabric.
Mega-Urban Development at Local Scale
Canary Wharf Debate
Canary Wharf mega-urban archetype. ‘City of
Spectacle’.
Economically very successful (likely to be hit by
downturn), public transport success but socially
divisive, live/work failure.
New Urban Form?
Street network fundamental to traditional city,
multiple functions key to success, but density
limits.
Innovations in London to overcome space
restrictions– London Underground
– Raised pedestrian concourse (failed).
– Multiple levels in mega-developments.
New Mega-Urban Developments
Intention is that newer developments avoid past
mistakes. Stratford currently showing familiar
signs.
Conclusions
Great Potential in Geography and Geometry Concepts
Integration of socio-economic and built environment data opens new research
possibilities. Shown particular employment and urban form structures in
London. Methodological challenges in integrating between scales.
Monocentric and Polycentric Discussion Important
Debate
Complex interaction of economic, social, and sustainability factors. Likely
greater potential for dispersed growth in London, but significant differences
between Outer Centres and Edge City.
Local Scale Factors
Ongoing research. Significant trends in mega-urban developments and Outer
London variation.
Analysis and Methodology Weaknesses
Missing Social and Demographic Considerations
Residential considerations (family orientated environments, housing market divisions) huge influence on
live/work relationships, as are education and skills disparities. Currently conducting housing market research,
need to integrate this with sustainability analysis.
Temporal Analysis
Density data fixed in time. Have access to London Development Database for new completions and
permissions, one route. Greater use of ABI employment data needed, currently problems at low spatial
resolutions.
Employment / Sustainability Simplifications
Various proxy measures should be more rigorous. Rent information also missing from analysis and should be
incorporated.
Technical Issues Regarding Spatial Joins
Can’t entirely avoid MAUP issues.
‘Physicalism’ Critique
Need to bear in mind, and focus on socio-economic links to urban form, not just urban form on its own.
Related Research Opportunities
Network Research
Building Energy Research
Land Use Transport Modelling
Lots more possibilities with new data and analysis
methods. Database intended to be used and contributed to
by other researchers (some licensing issues for particular
datasets).
Thank you for listening! Welcome comments and questions.
Contact Email: [email protected]
Like to thank the following data providers for this research:
Ordnance Survey
Valuation Office
Infoterra
Greater London Authority
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