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Designing Resilient Cities

Environmental impact assessments are today fundamental for practitioners, although there is a mixed feeling about them. On the one hand, the design of sustainable built environments is such a complex issue that inevitably the task must be facilitated through tools that can measure impact. Rating codes, which ultimately serve this purpose, are now integral part of the profession, and are specialised enough to cover different building uses and/or design strategies (e.g commercial, residential, refurbishment, passive solar, etc). On the other hand, they can limit innovative approaches, in that their structure indirectly privileges some technologies or strategies and does not recognise others. Moreover, the rating is predominantly given on the design of the projects whereas too often these, on post-occupancy evaluation, do not perform as claimed.

 
There is a further limit to current tools for sustainability: they don’t measure resilience. Resilience has recently become a recurrent term in the urban design debate, predominantly in connection with climate change and natural disasters. The term was initially introduced in ecological studies to connote the capacity of a system to survive because of its in-built adaptability. It is the case, for example, of some forests in Canada with a high population of a tree species threatened by parasites. If one examines the life cycle of the tree, the parasite is arguably a threat. But if one looks at the forest as a system, the effect of the parasite is benign, since it controls the number of a species that is particularly strong and could potentially overtake the space of other tree species. So the fluctuation of the population of that particular tree in function of the life cycle of the parasite is a sophisticated in-built resilience strategy that enables the forest to retain its many species living together. The lesson is that to understand resilience the scope of analysis must be broad and observed over an extended period of time. By the same token, a model of resilient city is one that is able to adapt and spring back to normal in the face of future environmental and societal changes. Built-in adaptation measures may not make sense from a narrow focus of examination (e.g. financial investments), but they become crucial if the focus is broad and holistic.
 
Resilience is about designing with the future in mind. But how can this be done if the future is uncertain? Scenario-based techniques can help identify future challenges. Scenarios have been used to analyse risks in relation to climate chance but also, more in general, to scrutinise the resilience of any type of plan against socio-economic future shifts. This seems important for the purpose of urban development. With large financial efforts invested to develop buildings and infrastructure we must ensure that these will resist climate change as well as a constantly changing market and society needs. Buildings may resist flooding, for example, but not changing patterns of demographics and household composition. Scenario-based techniques, however, are rarely used by practitioners, and there are no available easy-to-use tools for this purpose. With this in mind the Urban Futures project (an EPSRC funded research programme developed by University of Birmingham, University of Exeter, University of Lancaster, Birmingham City University and Coventry University) has developed one that can enable practitioners to test design schemes to resilience. This method of analysis is illustrated in ‘Building Resilient Cities’ a guide recently published by BRE, and can be performed through a free on-line design tool available at www.urban-futures.org.
 
At the heart of the Urban Futures (UF) method is a set of four scenarios portraying very different but plausible evolutions of society in 2050 against which design options are assessed. First, the conditions that will enable a particular solution or strategy to function over the lifetime of the development must be identified. Next, if these conditions are not supported in one or more future scenarios, causes can be detected and alternative strategies discussed. Scenarios are detailed through a list of characteristics (i.e. indicators) expressing quantitative and/or qualitative performances (e.g. water consumption, dwelling density, etc). These are key to provide an evidence base for the analysis. The method is flexible and can be applied at several scales and with different levels of detail (e.g. a particular building technology, a building, a masterplan, etc).
 
Lancaster – A case study
This analysis has been trialled on many case studies. The work developed on a regeneration project in Lancaster, for example, shows how this futures-based analysis can impact the initial environmental site strategy in order to build resilience. The planning guidance for that site issued some years ago by the Lancaster planning department is in the process of revision. The analysis was developed on the energy efficiency strategy with the intention of using findings to inform the new guidance. The UF analysis is context-sensitive. By focusing on the strategies for energy efficiency, it is able to find possible future vulnerabilities in relationship to the configuration of the site, the social composition of the area, the organisation of the future community, and more. In the present guidance there is a specific request to deliver energy efficient dwellings through maximised solar gains and natural light penetration. Being this the planned strategy, the avoidance of overshadowing now and in the future is a necessary condition to deliver energy efficiency. An unused railway embankment on the south side of the site is regarded in the planning guidance as a potential obstacle to the permeability of the place. It is suggested to encourage connections with the neighbouring community, maybe opening it and thus transforming its configuration.
 
The UF analysis identifies the transformation of the embankment as a potential threat to the future of the development in many ways. In scenarios in which market forces dominate, the planning system is deregulated. The partial demolition of the embankment leaves the fringes of the site vulnerable to new (maybe high rise) development, with consequent overshadowing. Instead, retaining the embankment in its present form would potentially serve many benefits: it could prevent future urban expansions/densification encroaching on the regeneration site and blocking sun access; it would retain the identity of the place strongly characterised on the south side by the system of embankment; it would contribute to the microclimate of the area in the perspective of future rising temperatures; and it could expand the city green infrastructure thus fostering biodiversity. Moreover, if correctly landscaped, it could also become a focus of attraction for (thus connect with) neighbouring communities. In other future scenarios in which environmental values drive policy and society, these green features will greatly contribute to the appreciation of the place.
 
Another requirement specified in the planning guidance is on-site renewable energy generation. The UF analysis shows that the ownership model is crucial to the success of this measure. Photo-voltaic and thermal solar panels (if this is the renewable technology selected) have components with a relative short life (15-20 years). Therefore, it will be necessary to replace them several times over the potential lifetime of the development, with consequent substantial investments. The regeneration scheme provides for 350 dwellings and 8,000m2 of commercial space. It is therefore important to question the capacity and will of each individual homeowner to invest every 15-20 years for substituting obsolete panels. In some scenarios this may not happen because of the scarce interest of society on environmental issues and/or because of growing inequality resulting in an increase of number of households living with low/low-medium income. A community ownership, with a management team and funds for running the scheme, would certainly offer a higher degree of resilience to the renewable generation scheme. This would entail an active involvement of planners and developers during the planning, construction, and post-occupancy phases to make this happen.
 
At present, we don’t know yet if the new revised planning guidance will integrate the recommendations resulting from the analysis. We know that the planning department was very receptive to these arguments. They seemed to understand that if they really want to rely on solar gains to reduce energy consumption, they need to think of the future risks that may undermine this objective. We are at a point in time in which we cannot afford to invest on strategies that may not deliver in the future what they promise. The way forward for this project is therefore either to ensure the embankment is protected, or to attain the energy target with (and therefore invest on) other strategies. Similarly, although micro-generation schemes are vital to reduce electricity demand from the grid, it could be unwise to believe these are an effective solution regardless of the particular situation where the scheme is proposed. If conditions to ensure resilient energy savings cannot be created, then other avenues may be explored.
 
For example, investments can be diverted on public/private partnerships for district scale renewable energy generation schemes, with reduced energy costs for the community.
 
Some of the arguments that the analysis elicited may seem rehearsed. Nevertheless the UF analysis provides important evidence to support modifications to current guidance, which would not have surfaced with traditional assessment methods. The integration of this analysis alongside current environmental assessment tools has not only the power to endow resilience, but also to change an engrained mindset of focusing on current necessities without considering the consequences that poorly formulated plans can have in the future.
 
Birmingham – a case study
This analysis has been trialled on many case studies. The work developed on a regeneration project in Birmingham, for example, shows how this futures-based analysis can impact the initial environmental site strategy in order to build resilience. In this project, sustainability is claimed through mixed-use and connectivity with the city centre by means of public transportation and provision of pedestrian access. Its high-rise towers are described as a new gateway to the city centre with the potential of becoming an urban landmark. These towers enclose a series of open spaces. The overlooking shops and restaurants are meant to attract people and create a thriving public realm. The masterplan provides for 80,000m2 of commercial space and 520 dwellings, mainly rather small studio, one, and two bedroom flats. This design choice limits the variety of future occupants which may result composed predominantly of singles and couples, thus limiting a balanced social composition of the place. The development has not progressed as originally planned, and to date only a small part of it has been constructed.
 
It was decided to analyse the design scheme in its energy efficiency. The UF analysis is context-sensitive. By focusing on the strategies for energy efficiency, it is able to find possible future vulnerabilities in relationship to the configuration of the site, the social composition of the area, the organisation of the future community, and more. In the design statement of this regeneration project there is no mention of any particular building performance exceeding mandatory standards. Therefore, it must be assumed that building fabrics comply only with the Building Regulations Part L in force when the scheme was granted planning permission. In future scenarios in which environmental values drive policy and society, this building fabric is not complying with tight building regulations, thus buildings as currently planned must undergo expensive retrofitting or be demolished. Instead, a level of building fabric efficiency higher than the current mandatory standard is supported in all scenarios, and can deliver energy savings no matter what the future holds.
 
The development is designed at very high density and with a limited range of dwelling types. In scenarios where market forces are powerful, high densities can be associated to a perceived low quality of the development. This could trigger a situation in which the place can become predominantly occupied by low income groups, thus being prone to mechanics similar to those of many council estates, in which a mixture of bad management, excessive concentration of disadvantaged families, and a lack of attachment to the place generate neglect and blight. In the scenarios where environmental values are high on policy agenda, or embraced by society as a whole, the place may be considered for expensive retrofitting or demolition since deemed highly inadequate to promote mixed use-mixed tenure communities.
 
The design scheme privileges high-rise building types at a distance close enough to limit the sun access and the penetration of natural light, with consequent rise in the use of artificial light. To appraise this assumption the masterplan was modelled in IES, and the Vertical Sky Component on all windows was measured. The appraisal confirmed that, overall, the performance of buildings is quite poor, with only top floors exceeding the minimum benchmark of 27% set by CIBSE. Instead, low and middle floors do not receive enough daylight. Moreover, open spaces lack direct sunlight for most part of the day, which would seem an essential feature for delivering a high quality public realm. Similarly to the results of the analysis for the building fabric, findings suggest that the lack of natural lighting could hinder the long-term appreciation of the development. A more resilient design configuration would require different spatial strategies that can retain the objective of creating an urban landmark and at the same time deliver places that stand the test of time. This would require designing for lower urban density. It would also require a careful investigation on the building forms from an aesthetic as well as an environmental standpoint. This approach would probably lead to wider distances between buildings and carefully shaped building profiles and footprints.
 
The UF analysis makes it possible to connect diverse urban parameters and to see how they influence each other. The case for a higher level of building energy efficiency developed through the analysis touches on the density planned for this scheme, the quality of public spaces, the social mix of the future occupiers, and the future commercial value of properties. Urban designers and planners are fully aware of the holistic nature of cities. Nevertheless, within the process of urban development, it is easy to lose sight of the consequences of decisions too often influenced by the pressures of stakeholders and their own (competing) agendas. The UF analysis provides arguments that are pertinent to all stakeholders and shows the full weight of consequences sometimes not evaluated because (wrongly) regarded as remote. The integration of this analysis alongside current environmental assessment tools has not only the power to endow resilience, but also to change an engrained mindset that focuses on the current necessities without considering the consequences that poorly formulated plans can have in the future.

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