Cities: places of complexity
Scira Menoni and Funda Atun (POLIMI)
Cities are complex three-dimensional spaces in which social, political and economic organisations interact in different ways and at multiple levels with buildings, infrastructures, production and service facilities, open areas. These interactions reflect the cultural features and the degree of technological development of cities and their inhabitants.
Cities share with complex systems virtually all features that characterize them as such. The first feature is the non-linearity between systems and components with the consequent impossibility to predetermine how the latter will interact with each other in the future or under changed conditions. A second feature derives from the “path dependency” of decisions made, particularly those regarding locational issues and the establishment of new urban functions in a previously not urbanized area. Third the difficulty to forecast the response to external forcing such as that imposed by natural hazards or severe man-made accidents. Other important aspects that need to be considered are: the fast evolution of the “urban” particularly in the more recent decades, implying differential development dynamics; the pressure to become more resilient, able to adapt to internal and external pressures and shocks; the multilayered governance of cities, resulting from a deeply transformed geography in which urban fringes tend to blur into rural areas making it very hard to define a clear cut border between what is “city” and what is not. An additional element of complexity derives from a simple quantitative datum: more than 54% of the world population lives today in cities, 75% in Europe, reversing any prior historic trend and requiring therefore highly skilled managers to keep cities function and able to respond to multiple stresses including natural disasters and man-made incidents. A cultural innovation is required from city managers and planners to overcome traditional perspectives and understanding of what cities are that were still relevant and viable only half a century ago.
The implications for DRR have been depicted very smartly in the Flood Risk Management Plan, strategic document prepared by the largest River Basin Authority in Italy, the Po RBA. In the scheme presented in the Plan, the need to integrate the objectives of the Water Framework and the Floods Directives is highlighted, showing that both are acting at the conjunction of social, environmental and economic systems. This apparently trivial representation actually introduces significant novelties in the way engineers and planners have conceived for disaster risk protection and prevention. It suggests that environmental sustainability needs to be coupled with risk prevention, meaning that at the city level the two cannot be kept separated anymore and that actually they should include also climate change adaptation. Fragmentation of programs and initiatives is not a viable option: because of the complexity of implied systems and their mutual interrelationships, a much more cooperative effort is required from the different branches of cities’ and regions’ offices in charge of individual policies and programs that have effects on each system and its components.
As can be seen in the case studies of the Umbria Region, Italy and Lorca, Spain, flood risk management plans are inherently multi-scale. At the river-basin scale it is possible to identify the most critical process and rivers’ sections. At this scale the effectiveness of both structural an social, political and economic organisations in non structural risk mitigation must be assessed, whilst at the city level individual projects aimed at reducing the risk locally must be implemented.
After the Industrial Revolution the relationship between the natural and the man-made environments of cities has been progressively overlooked, but nature has always constrained urban morphology and continues to do so. In more recent years, the “natural” in the “urban” has been rediscovered. Open spaces in cities have been devoted to urban agriculture, intercepting the still existing agricultural land and practices in the peri-urban; innovative projects have brought “nature based solutions” to reduce hazards such as floods and heat waves right in the core of cities. Those cannot be considered as fit for all solutions, but they clearly highlight different attitude towards natural spaces in cities.
Yet in general terms it can be said that cities where the link between natural and man-made environments has been addressed in a sustainable manner are also less exposed and vulnerable to natural hazards, while cities where such a link has been neglected display unsustainable patterns of development that make them also more prone to damage and disruption when stressed by natural extremes.