Quartiers résidentiels périurbains en transition : Comparaison multicritère de scénarios prospectifs à l'horizon 2050

Since the Industrial Revolution, urban spaces have undergone a profound reorganisation in parallel with a transformation of society and lifestyles. Urban sprawl has become widespread in Switzerland, as in countless countries, due to continuous innovations in transport, exponential population growth, land speculation and the ubiquitous desire to live in a single-family house. This process has led to a dispersion of the city in rural areas, which today raises multiple questions regarding sustainability aspects. In response to the negative consequences of urban sprawl, the model of the polycentric compact city sets a reference for the expression of ambitious spatial planning policies. The context, very favourable to inward densification processes in areas well served by public transport, changes the perception of neighbourhoods of single-family houses by providing them with a status of unexploited land reserve. A growing number of projects is investing this emerging field of research to address the challenges of under-occupancy of housing, energy insecurity or the production of new residential areas. However, some neighbourhoods, located in peri-urban areas benefiting from a relatively poor public transport service, are on the margins of current investigations. Proactive approaches are still rare to provide answers to the challenges faced in these existing residential sectors. The aim of this doctoral thesis is to develop a decision-support framework to consider the future of peri-urban residential areas and their participation in the sustainability transition. Anchored within the European and Swiss contexts, the work questions the transformation potential of neighbourhoods by 2050. The approach is divided into four phases, the first of which consists in developing a typology of peri-urban neighbourhoods of single-family houses. This typology is the result of a method based on the successive reduction of the analysis scale, from the theoretical definition of peri-urban residential municipalities to the census of representative neighbourhoods in the Greater Lausanne area. The design of prospective transformation scenarios is part of the second phase of the research. The five scenarios â Caducity, Exclusivity, Opportunity, Urbanity and Mutuality â are derived from stagnation or transition trends of peripheral sectors, identified during interviews conducted among about 20 experts. The third phase consists in applying the scenarios to six existing neighbourhoods over a 35-year time horizon. The thesis does not have as its sole objective to carry out forward-looking work applied to concrete cases, by proposing a medium/long-term vision. Its innovative character also lies in the implementation of an experimental tool of building information modelling (BIM) at the scale of the neighbourhood to deal with the complexity related to the constraints of individual ownership. Considering assumptions of demographic and temporal calibration of projects, the fourth phase, of multi-criteria assessment, is enhanced by a dynamic analysis of evolutions. This assessment, developed in light of sustainability issues, highlights a considerable potential for improving peri-urban neighbourhoods, through energy-saving building renovations and the preservation of quality living standards. The path towards more sustainable futures also depends on the coordination of decisions at the neighbourhood level to go beyond the mere juxtaposition of individual interests.

Peri-urban residential neighborhoods at the margins current trends in urban growth: towards sustainable transition paths?

Judith Elisa Drouilles, Sophie Lufkin

In Switzerland as in most European countries, the last decades of urban development have put much pressure on the environment due to uncontrolled urban sprawl. The existing peripheral residential built-up areas mostly composed of single-family houses are responsible for and subjected to many sustainability issues, which are expected to grow in the short/medium term. Focusing on urban and architectural design, this on-going research investigates possible paths for the future of peri-urban neighborhoods of single-family houses by 2050. The paper presents the intermediary results of several test-applications of prospective scenarios developed for two case studies in the urban region of Lausanne, Switzerland. First, this article briefly introduces the research framework of the peri-urban question in Switzerland by highlighting the specificities of the policy and territorial contexts. Second, it describes the design framework, focusing on the elaboration of a typology of peri-urban neighborhoods of single-family houses used as a preoperational tool to guide the design process. The core of the paper then focuses on the conceptual elaboration of four prospective scenarios foreseeing possible evolutions for peri-urban neighborhoods of single-family houses. To illustrate this approach, test-applications – in terms of urban and architectural design – are conducted in two existing neighborhoods. Finally, a limited list of indicators on density, land use and environmental impacts helps assessing the performances of each applied prospective scenario. The scenarios seek to be operational and feasible in a way to provide a decision support. The preliminary conclusions of the study highlight several initial conditions to bring peri-urban neighborhoods on a path towards sustainable transitions.

2018

Comparative multi-criteria assessment of urban renewal scenarios for existing neighborhoods

Maria Gracia Riera Perez

The growth of European cities in recent decades, mainly characterized by a decreasing density and a functional segregation, has tendentially increased mobility, soil consumption, urban sprawl, social disparities and infrastructural costs. Hence, most European countries have decided to aim for an urban sprawl limitation, in particular by increasing the density of built urban areas. To achieve this goal, new operations on unused urban areas are not sufficient, urban projects on existing neighbourhoods are also required. In a sustainability perspective, urban renewal goes beyond the issue of density. It has to integrate socio-cultural, economic and environmental aspects simultaneously. Based on a case study analysing the neighbourhood of "Fleurettes", in Lausanne, Switzerland, this paper shows how the diagnosis of the sustainability of an existing neighbourhood and a multi-criteria assessment of different scenarios, based on the use of the "SméO" methodology, can be an effective decision support tool for choosing an operational strategy. The results show that sustainability tends to increase with the level of intervention, especially in the field of energy consumption, but also by improving the quality of life, by promoting soft mobility, by offering green public spaces and by providing return on investments. Consequently, the research confirms the interest of the different protagonists (public administrations, private owners, investors, designers and users) to jointly explore possible synergies for the sustainable development of existing neighbourhoods.

2012

Méthodologie de gestion durable des ressources du sous-sol urbain

Pascal Blunier

The world is becoming more and more urban. During the last fifty years, the population in Swiss cities has grown from 45% to 70% of the total population. This change is characterised by urban sprawl and by an increase in the consumption of resources, particularly those coming from rural areas. This evolution is not compatible with the principles of sustainable development. To solve this problem, new urban policies are being developed. They favour development within the urbanised areas and reduced use of exogenous resources. The urban underground contains resources – space, geomaterials, groundwater and geothermal energy – which can efficiently support such policies. This project analyses how these resources have been exploited until now and how they could be used with sustainability in mind. The use of underground resources was analysed in five cities : Mexico, Paris, Helsinki, Tokyo and Montreal. It appears that, although resources participate in the urban metabolism, there is an important lack of planning and coordination in their use. Developments follow a sectional approach where the resources are considered independently, and only at the scale of a given construction project. As a consequence, conflicts occur between uses and resources are wasted. An understanding of the urban underground as a system was developed with the aim of preventing conflicts and promoting synergies. To this effect, the way in which resources interact was considered attentively. Situations in which interactions occur were described and analysed and compatibility conditions were suggested. A methodology was elaborated to evaluate the resource potential of an urban underground. It aims at considering the resources and the interactions between their uses from the beginning of the process of urban planning. The methodology is based on the use of Geographical Information Systems and 3-D modelling of geological and hydrogeological conditions. It aims at reversing the current paradigm, that proceeds from the needs to the resources, into an approach based on resources to satisfy the needs. Spatial information was exploited to determine indicators and maps of potentiality and of restrictions. The derived results will help support decision making by planners and policy makers who seek to better exploit the resources from the urban underground. The methodology was tested and applied on a case study : Geneva. The developed approach allows more efficiency in the use of urban underground resources, it can help prevent conflicts between uses and develop synergies. When integrated in the urban planning process, it highlights new opportunities and helps to develop projects that take into account the physical conditions of the underground.

EPFL2009

Méthodologie de gestion durable des ressources du sous-sol urbain

Pascal Blunier

EPFL2009