Integrated Urban River Corridors: Spatial design for social-ecological resilience in Bucharest and beyond

This thesis focuses on Urban River Corridors (URCs) as spaces of social-ecological integration par excellence–that is, spaces where the interaction between the urban systems (carrying the ‘social-’) and the river system (carrying the ‘-ecological’) is (potentially) the most intense. The general hypothesis is that with an integrated spatial understanding, planning and design of rivers and the urban fabric surrounding them, cities could become more resilient, not just to flood-related disturbances, but to general chronic stresses as well. Hence, the thesis addresses a number of spatial problems arising from the loss of synergy between the natural dynamics of rivers and the spatial configuration and composition of urban areas that they cross, namely: the relationship between fluvial geomorphology and urban morphology weakened by river-taming operations; the physical barrier caused by riverside vehicular traffic; the latent flood risk built up through resistance-based flood-protection measures; the diminished capacity of urban rivers to provide ecosystem services; and the reduced scalar, (and implicitly) social and ecological complexity of urban rivers after rationalisation.

Drawing on theories of social-ecological resilience and urban form resilience, on conceptual and analytical tools from the fields of spatial morphology and landscape ecology, and on explorations through urban river design projects, the thesis departs from the research question

“How can social-ecological integration be spatially defined, assessed and designed in Urban River Corridors?”

Accordingly, it constructs a theory of social-ecologically integrated Urban River Corridors, in which it proposes a spatial-morphological definition, an assessment framework, and a set of design principles and design instruments. These three components of the theory represent the descriptive, analytical, and normative claims advanced in the research, respectively. The thesis employs a mixed methods research strategy that combines methods of both quantitative and qualitative nature as part of a transdisciplinary design study approach. As the object of the design study, the case of Bucharest crossed by URC Dí¢mboviÈ›a and URC Colentina is used to contextualise the spatial-morphological definition, and to demonstrate, develop and test the proposed assessment framework and design principles, with a distinct set of methods in each of the three parts of the thesis.

The first part places URCs in a wider theoretical and empirical context. A transdisciplinary literature review is carried out to distil environmental-ecological, social-economic, planning-governance and spatial-morphological knowledge into four key properties of URCs–connectivity, open space amenity, integration and multiscalarity–and to adopt a method of URC delineation. A historical overview of Bucharest’s URCs and a qualitative data analysis of 22 expert interviews is conducted to describe the past dynamics and the current state of URC Dí¢mboviÈ›a and URC Colentina. The history of the two rivers shows a process of radical transformation from a flooding and dynamic river valley to a canalised stream and cramped urban space (River Dí¢mboviÈ›a) and from a pestilential wetland to a succession of lakes and parks designated as a metropolitan recreational area (River Colentina). In the expert interviews addressing the current state of the two URCs, Dí¢mboviÈ›a was described as inaccessible, disruptive, unattractive and artificial from both social and ecological point of view, but also, in terms of potentials, as a major axis of urban development and potentially the largest public space of the city. URC Colentina, as revealed in the analysis of the expert interviews, is currently inaccessible and fragmented by lakeside privatisation and it lacks cohesion due to contrasting social and spatial peripheral conditions. Yet, most experts considered that it is potentially the largest recreational space and green corridor in the metropolitan area of Bucharest.

Based on the spatial-morphological definition of URCs and on existing approaches to assessing urban rivers, the second part of the thesis develops an assessment framework, that is, a structured indicator system and a method for the assessment of social-ecological integration. The indicator system is structured in a hierarchy of social and ecological categories under connectivity (longitudinal, lateral, and vertical connectivity) and spatial capacity (spatial diversity, quality and composition). The method of assessment confronts values given by indicators from corresponding categories (e.g. social lateral connectivity with ecological lateral connectivity) in a mirrored social-ecological assessment chart and highlights areas of potential for improved social-ecological integration on the scales of the corridor and the corridor segment. Informed by the key problems and potentials derived from the analysis of the expert interviews, a complete assessment is carried out on URC Dí¢mboviÈ›a and a demonstration of wider application is given on URC Colentina. Corridor-segment assessment shows that URC Dí¢mboviÈ›a currently has a high-to-medium longitudinal connectivity, medium-to-low lateral connectivity and low vertical connectivity, as well as a medium spatial diversity and quality, and a medium-to-high spatial composition. The social-ecological profile of URC Dí¢mboviÈ›a highlights potential improvements on the ecological dimension for centrally located corridor segments and a potential increase in spatial diversity and composition on the social dimension in peripheral segments. The application of the assessment framework to different site conditions is briefly demonstrated on URC Colentina with an indicator of street network accessibility (also used in the assessment of URC Dí¢mboviÈ›a) and green space coverage (specific to URC Colentina).

Building on principles of urban and landscape design and informed by design explorations through four urban river projects carried out by the author, the last part of the thesis develops four design principles, namely Interconnectedness, Absorptive Capacity, Social-Ecological Integration, and Interscalarity, derived from the key properties specified in the spatial-morphological definition of URCs. Interconnectedness and Absorptive Capacity are principles that guide the design of elements found in the networks and open spaces of the URC, while Social-Ecological Integration and Interscalarity reveal systemic and scalar relations among those elements. Finally, the design principles are translated into four corresponding design instruments–the Connector, the Sponge, the Integrator and the Scaler–, meant to aid designers in building social-ecologically integrated URCs. A design workshop organised in Bucharest is employed to demonstrate and test the use of the design instruments in the design process and their impact on the design projects. The workshop participants evaluated the design instruments as overall useful and easy to use, but also gave valuable suggestions for improvements in their application in the design process.

The thesis concludes with a reflection on theoretical, methodological and practical implications of the research. By drawing parallels between the spatial-morphological definition, assessment and design of URCs, on the one hand, and the spatial properties and models of social-ecological resilience, on the other hand, it argues that social-ecologically integrated URCs have a potentially positive impact on general urban resilience. This last part discusses challenges and opportunities of the transdisciplinary design study approach and the mixed methodology, gives possible usage scenarios for the assessment framework and design instruments, and reflects on the wider applicability of the research for urban and landscape design beyond the case of Bucharest.