Predetermined? - Systems Thinking for the Urban Subsurface

In recent years the topic of urban underground projects and infrastructure networks as well as their contribution to sustainability and resilience of cities has been widely addressed. Major projects deal with questions of interdependencies, mapping and untangling of the existing underground infrastructure web, which constitutes not only a service but also a major constraint for future projects and planning in the underground space. In addition, the use of urban underground space is more and more extended from purely 'technical' functions like infrastructure and storage to developing the space itself into, for example, shopping malls, extensions of museums or parking facilities, recreational spaces, archives, or computer centres. To capture and plan for these manifold interests in the long-term, a holistic approach to analyse the urban subsurface is needed which goes beyond the analysis of singular projects or networks. Masterplans which integrate the subsurface seem to be feasible but ultimately can only be successful if the underlying system properties are sufficiently understood. This paper reviews the development of system thinking as well as its applicability for analysis of the urban subsurface as multifunctional, holistic entity. Prospects and outstanding issues when adopting a systems perspective to a spatial entity are discussed in order to interpret what they might mean for the urban subsurface. In this context, the influence of system boundaries on system properties like flexibility, adaptability and resilience is highlighted, challenging the notion that the potential for further exploitation of the subsurface is predetermined by the local geology, the legacy of human impact and the advancement of technologies.