Special issue  

This special issue aims at providing an extensive overview about how researchers, practitioners and professionals are integrating the resilience concept to set up new risk management approaches and to design more resilient and flexible cities to face all types of natural hazards, including multi-hazard conditions and cascading effects. Indeed, many research and operational projects are focusing on resilient pathways to mitigate different types of risks in urban environments. This NHESS special issue represents a great opportunity to reflect on new developments and results addressing research and practice on resilient urban environments in many geographical contexts. We are expecting articles presenting specialized disciplinary research, combining different disciplines, addressing transdisciplinary concepts and solutions, and presenting theoretical and conceptual elements on resilience but also tangible applications. All methods, frameworks and tools (GIS, spatial decision support systems, observatories, etc.) designed to reduce risks in urban areas by integrating resilience concepts are welcome in this NHESS special issue.

Indeed, 2007 was a crucial year when the threshold of 50% of the population living in urban environments was achieved. Ten years later, many natural hazards and often a combination of hazards affects the urban environment everywhere in the world. This becomes even more pressuring when considering that 68% of the global population will be living in cities by 2050. This increase rate corresponds to a new city of 1 million people every week during the next 40 years. This exponential curve is sufficient to imagine that urban environments will become more vulnerable: risk management issues we will have to deal with are becoming more complex. Activities and concepts based on past experiences must be questioned – the future will be different and this needs to be addressed. This includes that quick urbanization comes with climate change uncertainties. Climate change, coupled with people and asset concentration in such environments, is the worst combination to set up a sustainable natural hazard management plan. As an example, floods are considered the major natural hazard in the EU in terms of risk to people and assets. Currently, more than EUR 40 billion per year is spent on flood mitigation and recovery in the EU. More than 75% of the damage caused by floods is occurring in urban environments. In the last years, flash floods have emerged – causing considerable damage in areas where these hazards have not been known and experienced before. Global changes (e.g. concentration of population and assets in urban areas) including environmental change (e.g. vegetation and climate change) are the main trends likely to affect these numbers in the near future. Global warming is expected to lead to more severe and intense storm and rainfall events, to prolonged heatwaves and drought periods, and to increasing high-flow but also low-flow river discharges and sea level rise. This means that hydro-meteorologically related risks are likely to increase significantly. Urban systems contain assets of high value and complex and interdependent infrastructure networks (i.e. power supplies, communications, water, transport). These infrastructure networks are critical for the continuity of economic activities as well as for people’s basic living needs. Their availability is also required for fast and effective recovery after disasters (floods, hurricanes, earthquakes, landslides, etc.). The severity of damage therefore largely depends on the degree that both high-value assets and critical urban infrastructure are affected, either directly or indirectly.

Contributions dealing with one or combined topics described above are welcome.