Case studies in quantitative urban sustainability

A sustainable city is one that relates its use of resources and its generation and disposal of wastes to the limits imposed on such activities by the planet and its organisms. Drawing upon a study that proposes quantifiable urban actions related to sustainability, we designed three cities with common characteristics but in different geographical and climatic regions (Vietnam, Namibia, Serbia & Montenegro). The intent of the designs is to maintain sustainability as the city evolves over a 20-year period. Several lessons emerge from these case studies: (1) The imposition of quantitative sustainability requirements poses no substantial barriers to the design of workable cities over a range of quite different geographic and climatic conditions; (2) Accommodating evolution is important to sustainable city design; a city can potentially be sustainable at some stages of its evolution but not others; (3) Cities can never be designed and built as totally isolated systems, so sustainable design is ultimately a hierarchical exercise with cities at a low level and the entire planet at the top of a multilevel system, each element of which must contribute to its sustainability.