Integrated Spatial Planning for Resilience and Sustainability
Abstract: As cities grow, we have to take into
account the increasingly complex inter-dependencies in the different urban
systems that make up a city. Spatial planning has a strong impact on both the
energy demand, the energy supply, and on the livability and economic
productivity of cities. Thus, we need a systemic approach which should be based
on 10 key spatial planning principles, including connectivity across scales，integration of transit and land use,
integration of spatial planning and economic densities, job and housing balance,
social inclusiveness, local accessibility, good-quality public space, mixed use
functions in communities, fine grain land market, value capture.
Keywords: integrated spatial planning,
connectivity, land use, density, transit-oriented-development, public space,
accessibility, fine grain, value capture finance
Abstract: As cities grow, we have to take into account the increasingly complex inter-dependencies in the different urban systems that make up a city. Spatial planning has a strong impact on both the energy demand, the energy supply, and on the livability and economic productivity of cities. Thus, we need a systemic approach which should be based on 10 key spatial planning principles, including connectivity across scales，integration of transit and land use, integration of spatial planning and economic densities, job and housing balance, social inclusiveness, local accessibility, good-quality public space, mixed use functions in communities, fine grain land market, value capture.
Keywords: integrated spatial planning, connectivity, land use, density, transit-oriented-development, public space, accessibility, fine grain, value capture finance
In the next 40 years the number of people in cities will double. Cities cannot be built as in the past. Resource limitations must be addressed. We need to rethink and redesign the totality of infrastructure for the cities of tomorrow. The infrastructure decisions we make today will be in place for a very long time. So, we need to build the foundation for the next 40 to 100 years. Spatial planning has a strong impact on both the energy demand, the energy supply, and on the livability and economic productivity of cities. As cities grow, policy makers and land use planners have to take into account the increasingly complex inter-dependencies in the different urban systems that make up a city. Only a systemic approach addressing energy issues through the scales that make up a city can address successfully the challenges of the energy productivity in urban systems. This systemic approach should be based on 10 key principles addressing urban spatial economics, transport and land-use integrated planning, urban design and energy planning in an integrated and systemic way through different scales. These 10 key spatial planning principles achieve significant co-benefits in areas usually separated in planning efforts and allow bundling urban policies for sustainability and resilience with policies for ensuring sustained economic growth and competitiveness, and with policies to ensure social inclusion and affordability.
1. Connectivity across scales is key for global competitiveness
Connecting people to people and people to jobs in a seamless integrated way though many modes (planes, HSR, regional trains, subways, buses) and across many scales is essential for economic development and for resource use minimization. Seamless integration of scales and modes should be ensured in efficient and compact interchange hubs that are high opportunities for urban development provided they are open on permeable, pedestrian oriented, and vibrant neighborhoods. Connectivity across scales ensures resilience of networks. A connected network pattern (streets, energy, information) similar to a leaf structure, with connections of all ranges and scales connecting directly at the same level in the hierarchy, is resilient, adapts itself to variable flows (avoids congestions) and reorganizes its flows when a part is damaged.
London's Jobs densities are clearly clustered around subway stations
2. Integration of transit and land use: Densities must be aligned with transit accessibility; Jobs accessibility by transit in 30 minutes fosters local development
Integrating the space economy and jobs & economic densities with transit accessibility (that-is clustering jobs and people at high densities around a hierarchy of transit nodes with plans specifying highly differentiated FARs) leads to high transit ridership, low car ownership, low transportation energy & GHG emissions, low infrastructure costs and associated embodied energy, and higher economic productivity per unit of land. Efficient intensity of development at metropolitan scale follows accessibility to people, jobs and commercial space at 30 minutes by transit (as can be measured today by big data algorithms) reinforcing the already dense and accessible areas, which have a high potential for growth, rather than dispersing development with decentralization policies and new towns.
As in any system, optimization should start at the higher scales of the urban system, that-is a compact distribution of people and jobs densities through the urban space and their alignment with transit accessibility. Sprawl (fragmented leapfrog urban growth where urban built footprint grows much faster than population) is extremely resource consuming. A city like Atlanta, for example, emits 10 times more CO2 /people/ year for transportation than Barcelona that has a larger population but is more compact and has a 26 times smaller built footprint. Urban Morphology and complex System Institute research has also shown that urban GDP is distributed according to a Pareto principle with 20% of urban land producing 80% of its GDP while 80% of the urban land produces only 20% of the GDP1. Networks lengths/km2 and costs/km2 decrease only smoothly with urban expansion2, thus as GDP decreases more sharply than infrastructure costs, beyond a certain radius of urban expansion infrastructure lengths and costs (and embodied energy in infrastructures) become higher than additional economic output, resulting in both an economically and environmentally inefficient urban form.
To address these issues, Transit Oriented Development (TOD) advocates increasing densities around transit nodes in mixed-use neighborhoods based on small blocks and a high density of intersections ensuring livability, urban vibrancy and local accessibility to transit stations.
Recent work by the Urban Morphology and Complex System Institute has shown that the shape of transit networks and the shape of densities in global cities, such as Paris, London, New York, Tokyo, Hong Kong, follow optimal shapes characteristics of complex systems that are both efficient, resilient, and low energy. First, subway networks converge towards optimal shapes made of a dense core of between 4 to 6 km radius, with a constant and uniform density of stations that are highly interconnected and ensure accessibility to stations at less than 500m for most residents and jobs. Radiating from the core, spokes extend outwards. At the limit of the core the density of stations drops and decreases sharply when moving away from the core3. The core is the area with the highest accessibility4 and should concentrate jobs at high densities for both ensuring high agglomeration economies and accessibility to a high number of jobs from the radiating spokes. Twenty minutes door to door by walk and transit defines the maximum area where forces of agglomeration shape high economic densities in one or several poles in global economies. Cities like London, New York, or Tokyo show a moderately polycentric shape within the core where the secondary poles are very close one to the other in a very compact organization highly interlinked by transit (at 20 minutes by transit from Midtown to Lower Manhattan, or around Tokyo’s Yamanote loop line that surrounds an area of only 60 km2, and at only 20 minutes between the City of London and Canary Wharf).
Recent work by the Urban Morphology and Complex System Institute has also shown that accessibility to a high number of jobs in 30 minutes by transit determines local growth in efficient market economies (residents + jobs densities increase with the number of accessible jobs leading to real estate growth and land values increases that are necessary for value capture and for starting a positive feedback loop for financing infrastructures and public realm). Thus the optimal structure for integrating spatial planning and transit accessibility is increasing jobs densities at the core of the transit system and increasing FAR both for population and jobs around transit stations in spokes radiating from the core.
This policy has allowed Hong Kong to ensure that 75% of its population and 84% of its jobs are located less than 1 km from a mass transit station, achieving a decoupling between economic growth and CO2 emissions per capita. Between 1993 and 2009, GVA/ capita increased 50% while CO2 emissions per capita and road gasoline per capita decreased about 10%.
3. Integration of spatial planning and economic densities
Agglomeration economies under market forces create high peaks of jobs densities
In efficient and competitive cities, such as London and New York, one third of the jobs are agglomerated in about 1% of the metropolitan area creating intense knowledge spillovers, while the other two-thirds are clustered around transit stations. Jobs and companies densities in global economies show that jobs densities increase productivity, competitiveness and job creation. One third of New York City and Greater London jobs (1.5 million jobs of these two cities of 8.5 million inhabitants) are concentrated in only 15 km2 in each city while New York covers 790 km2 and Greater London covers 1,572 km2. The command functions of these advanced services economies are even more concentrated with 29% of Inner London office space concentrated in less than 1% of its area, in the City of London (450,000 jobs in 2.9 km2 with a growth of 30% during the last decade) and with 60% of New York City office space concentrated in 9 km2 in Manhattan, that is in about 1% of NYC area. These extreme concentrations peak at 150,000 jobs/km2 and are made livable by high quality public space like in London’s Canary Wharf. The other two thirds of the jobs are distributed in these 2 global cities for their most part along transit corridors and around transit nodes, ensuring globally that about 2/3 of the jobs are less than 1 km from a mass transit station. High accessibility to jobs across urban scales (locally by a good job/housing balance; and at city scale by the alignment of jobs densities with jobs accessibility in particular with a high density of jobs at the core of the transit network) ensures that many localizations within a TOD city have access to a high number of jobs and thus have a high growth potential and a high land value.
4. Job/housing balance is key for a balanced development at local scale
Job/housing balance is key to ensure inclusiveness and reduce commuting time. It can be jeopardized by excessive decentralization policies. Job/housing balance at local scale is key for ensuring local vitality and development around transit nodes. It is not contradictory with a high density of jobs at the core: Manhattan, Seoul, and Tokyo have also high residential densities (21,000, 16,000 and 15,000 inhabitants/km2 respectively). The other 2/3 of the jobs at high density around transit nodes ensures a balanced local development at metropolitan scale. Low-density (FAR around 1, and density around 3,000 inhabitants/km2) mono functional new towns, far away from city cores such as Science Parks should be avoided as they contribute to sprawl and increase the cost and embodied energy in networks.
5. Inclusiveness: TOD can unlock land for affordable housing
An inclusive society is based on access to a large number of jobs opportunities for all (that can be ensured by transit-oriented development following the above principles), and by affordable housing located around transit nodes. High concentration of jobs at high densities in urban cores should be complemented by specific policies to increase jobs accessibility by transit in deprived areas. Inclusionary zoning should ensure affordability as in the United States. Hong Kong example shows that public policies based on value capture for financing public goods has unlocked land for 600,000 new housing units in the New Territories between 1970 and 2010 in areas with excellent access to mass transit and high number of jobs in reasonable commuting time below 30 minutes.
6. Local accessibility must be based on a dense network of connective streets
Accessibility within the transit network should be completed by a high level of local accessibility around transit nodes, often referred to as the ‘last mile’ issue. This is achieved by a high density of connective streets with, in international competitive cities, about 100 intersections per km2. Urban developments should be based on a fine grid of connective streets defining small blocks. Superblocks 400 m side and large arterials with setbacks should be avoided. The most successful world city, New York, is based on a grid of 30 meters wide avenues and 20 meters wide streets defining blocks 60 meters wide and in most cases 160 meters long. 10.000 m2 is the optimum size for an urban block, an urban square and an urban garden, although to ensure variety some elements should be smaller and very few bigger.
7. Public realm is key for livability in high-density areas
Public realm fosters social interactions, makes the urban environment livable and creates financial value. It should be continuous, with no gates, with streets as places for people and people centered. Many small gardens in the urban fabric are part of strategies of densification + greenification, like in Rotterdam, and contribute to a bioclimatic urban fabric enhancing solar gains, natural ventilation and cooling and reducing heat island effect, while ensuring 10-minute walk accessibility to public parks for all, such as in Singapore and Manhattan. High quality public realm is key for livability. It is based on a high density of connective narrow streets designed as places for people, shaded by trees and with benches, on plazas and gardens at a small scale, on a free flow of public realm without physical barriers, such as barriers separating sidewalks from streets of gates surrounding blocks. Public realm is created when small buildings aligned along streets with transparent shops define street edges. It is also based on design principles to make outside space an enjoyable public realm for people, with a sense of place created by design principles such as a well-defined and memorable space, with a sense of enclosure, human scale, transparency offering views, complex and rich information field offering a wealth of details at different scales, while ensuring coherence, legibility and linkage between urban spaces.
8. Mixed-Use at fine grain scale ensures diversity
Fine grain, mixed-use and diversity are essential to ensure that communities are friendly to people and offer them all daily amenities at walking distance. The mix of uses should be achieved at very fine grain (200 m2 plots in NY) and within the same buildings whenever possible.
9. Fine grain land markets, bottom up processes, and incremental growth are key to the economic resilience of adaptive cities evolving under market forces
Incremental growth ensures the city adaptation to economic, social and market changes. Fine grain platting with plots of 200 m2 in Manhattan grid plan has created a vibrant land market and land value increase has been captured for the city growth. New York growth has been based on a vibrant land market based on tiny plots of 200m2. On an area of 66 km2 such as Manhattan area, there were originally 300,000 plots of land - to be compared to only 250 in Chinese superblocks developments. This small-size land market has ensured a high variety of development types and a resilient and adaptive urban form. 40% of original plots dating back 2 centuries ago still exist in Manhattan - the command city of 21st century global economy - with 19th century brownstones while other plots have consolidated in a high variety of sizes from medium scale buildings to skyscrapers. These fine grain land markets are quite the opposite of Chinese very coarse land market based on superblocks. Fine grain ensures adaptive resilience to ever changing economic conditions with bottom up processes constantly increasing the diversity and complexity of the city through incremental growth.
10. Financial sustainability of integrated transport and land use schemes
is ensured by the positive feedback loop of value capture finance
High accessibility to jobs - procured by major transit investments, and transit and land-use integrated planning - ensures high land values and, provided land markets are flexible and incremental as described above, these values can be captured to finance transit infrastructure, public realm enhancement and affordable housing near transit. Value capture finance represents an innovative means of maximizing a city’s assets. It is a finance mechanism, which not only shares the risks and costs of urban development between public and private actors, but also the rewards. Value-capture finance sees some of the costs associated with making urban development succeed internalized within the balance sheets of the developments themselves. Public goods are consequently provided by urban development without the proportional draw on the public resources, which would otherwise finance them. Despite their breadth, value capture finance mechanisms have a unique common denominator. They involve a financial positive feedback loop with four components: value creation; value realization; value capture; local value recycling.
Value creation is the unlocking of, and increase in the potential value of under-used assets (land and/or structures) as a result of a public sector intervention to stimulate demand from the private sector. Value realization is subsequent investment and development from the private sector, which ensures that potential asset value increases. Value capture is arrangements by the public sector for the acquisition of a proportion of private sector returns for local reinvestment. This can take the form of monetary or in-kind contributions from the private to public actors. Value recycling is the reinvestment of acquired monetary or in-kind contributions from the private sector within the same development site or scheme. This re-investment can pay for the initial public intervention but tends to fund further interventions. These further interventions must have a public good element to them but may also benefit the private sector by consolidating value gains already made. As an example of successful value capture policy, the construction of Hong Kong subway did not cost anything to Hong Kong municipality budget and the local authority got 14 billion US$ profit through the joint development of transit infrastructure and real estate development along transit lines.
(This article was contributed by Serge Salat, President, Urban Morphology and Complex Systems Institute, Paris, France, June, 2016)
1 This is verified with the differences in GDP between Inner London and Outer London, and has been verified under the form on an inverse power law of exponent -1 in a detailed study of Zhengzhou and is more broadly confirmed by the universal power law with an exponent close to -1 that organizes the distribution of jobs densities in the urban space in Paris, London and New York.
2 At the power - 0.5 while GDP decreases at the power-1.
3 The sharp decrease in the density of stations with the radius from the city center follows an inverse power law of the form R - 1.6
4 This accessibility and connectivity that is higher in the core of the transit system can be measured by different indexes of centrality derived from graph theory: degree centrality measures the number of connections of a given station and is a measure of its connectivity; closeness centrality measures the distance on the network to all the other stations and is a measure of accessibility; betweenness centrality measures the number of shortest paths that go through a station, and thus its capacity to capture a high number of passenger flows and is a characteristic of stations that articulate different scales or different sub-systems in the network. Recent work by the Urban Morphology and Complex Systems Institute has shown that the different types of centrality translate into different probabilities of growth at local scales (for example betweenness and degree centralities in Tokyo’ Yamanote line and London’s Circle Line translate into high probabilities of growth like in Shinjuku or King’s Cross) and that centralities in the network should guide densities distributions and land uses planning by setting FAR’s at higher values in the most central places of the transit network.