Underground urbanism: Master Plans and Sectorial Plans

Highlights

• Best practices related to urban underground space planning have been described.

• Integrated Master Plans allows considering the long term interaction of multiple land use layers.

• Experiences of Integrated Urban Master Plans are limited, but many sectorial underground plans have been implemented.

• Geographic Information Systems can help managing multiple layers information.

• Integrated Master Plans are fundamental tools for a transition toward smart cities.

Abstract

The urbanization process leads many urban areas and megacities to be densely built and to overcome their physical and operational limits; in several cases, urban population density is growing faster than their infrastructures. Considering land use constraints, for mitigating some disagreeable living conditions and for creating new population opportunities, city planners have different opportunities involving the two opposite vertical directions: upward, erecting higher buildings or downward, developing a more intense use of the underground space. Both directions are characterized by positive and negative aspects and require suitable local condition to be built.

In this paper, main issues related to the urban underground planning procedures are highlighted, taking also in consideration that after some very old visionary approaches, no relevant debates and concrete results have been further developed. Several underground-related technicalities are described and analyzed, mainly at sectorial level (f.i. mass transport systems, infrastructures for energy and water supply, storage facilities) however, experiences of a global urban planning – involving a holistic approach inside a City Master Plan – are still very few (Helsinki). A collection of some best practices is reviewed in this paper. Particular emphasis is devoted to the integrated planning approach and the related tools for the subsurface space assessment: the role of different planning tools for the rational use of the underground space in urban areas is analyzed and a variety of planning levels are discussed, from the more general one – the Master Plan – to the more sectorial ones. Moreover, the more recent visions for future cities – Smart, Resilient, Low-carbon and Post-Carbon Cities – are producing relevant and very useful technical and management solutions and the role of Integrated Mater Plans in this transition is further discussed.

Introduction

The worldwide urbanization process, together with population growth, is increasing the pressure on urban areas leading to a higher attention on underground constructions. Nowadays, underground space is gaining a central role in the development of the structure of the city and of the urbanized areas, for mass transport and land savings, for energy distribution and storage, for new shopping centres and malls. The two dimensions of urban development, above- and under-ground, require suitable local conditions and both are characterized by several benefits and barriers: buildings above ground could produce negative effects on life quality connected to the increased concentration (in terms of activities, buildings, and traffic) if they are not associated to general planning choices and processes (Durmisevic, 1999, Parriaux et al., 2006, Besner, 2007). On the contrary, the development of underground space use is able to achieve benefits associated to the displacement of activities and infrastructure from the surface (new open spaces available, increase of green and quality of life), but requires a good knowledge of the sub-surface physical environment for preventing undesirable effects (Kraas et al., 2005, Parriaux et al., 2007).

The growth of cities, particularly in developing countries, the aging infrastructure in older cities, the demand for environmental protection and for better living conditions are creating a strong demand for new underground solutions and new underground infrastructures, representing an alternative to the above ground systems.

Three main categories of infrastructures involved are:

• services, commerce and administration facilities (e.g. shopping mall, leisure installations);

• mobility systems (e.g. people and freight transport, car parking, pedestrian walkways and bicycle paths);

• technical systems (e.g. telecommunication, sewage networks and treatment plants, industrial storage facilities) and infrastructures for the management of energy and water supplies (e.g. delivery, maintenance and storage).

Planning underground systems calls for an integrated approach, which considers the interests of many parties, the dynamics of different activities, and the potential threats posed by hazardous materials (Beroggi, 2000). Moreover, a suitable integrated planning approach could mitigate the trend of resident population and large commercial centres to move toward decentralized areas: the development of commercial and leisure activities in the downtown underground, easily linked to mobility nodes and associated to the diffusion of pedestrian districts gives new life to central districts (in which typically there is the higher density of underground infrastructures) (Bobylev, 2009). This aspect is increasingly important: in fact, historic top-down development of urban underground infrastructures and shortcomings in its planning have resulted in a lack of available underground space for new developments (Sterling, 2005). In this regard Sterling (2005), affirmed that it is too late to manage underground space use through planning policies in the majority of the near-surface zones in old cities. The results of several projects made in last decades, the experience acquired in managing these initiatives, together with the development of many technical tools (GIS, 3D visualization and CAD software, for instance) offer additional and powerful capability for subsoil planning purposes.

Since the pioneering works of Hénard (1911), all the main topics related to the underground space design, construction and management have been widely developed by scientists, urban planners and politicians and are accessible in technical literature. However, in the every-day practice, experiences of a global urban planning – involving a really holistic approach inside a City Master Plan – are very few; while there is a large diffusion of sectorial initiatives and researches that involve separately mass transport systems (Cui et al., 2013) (metro, roads, parking), infrastructures for the management of energy and water supplies, sewage treatment plants, safety analysis, telecommunication networks, commerce and leisure installations and industrial storage facilities (Utudjian, 1966). From one side, the displacement of infrastructures in underground is useful for providing additional surface land for housing and commercial activities or simply for preserving/improving the urban landscape; from another side, additional resources are added to the surface land managed by the “traditional” Master Plans: the underground space itself, the groundwater, the excavated materials and the geothermal sources. As a result, the “3D urbanism” could play an important and essential role in developing new sustainable urban solutions (Canto-Perello et al., 2013).

In this paper, underground space utilization in a rational land use perspective and its role in a sustainable planning process is analyzed and described at different levels for representing the major trends in Master Plans: integrating underground planning into the whole city Master Plan and producing dedicated Underground Master Plans. In sections one and two, best practices realized all over the world concerning both underground Master Plan and sectorial plans are described. The third section is focused on significant examples of sectorial approaches, like specific installations for commerce and leisure, systems related to transportation and technical systems. Concerning well planning practices, all of the described Sectorial and Master Plans have representative characteristics. In the fourth section, the role of Design Guidelines, Rules and Regulatory Bodies as well as of the supporting technical tools – like GIS and Geo-Radar – is highlighted.