Koen Olthuis is an active member of the Flood Resilient Group. Waterstudio supports the Flood Resilient Group by conducting and sharing beneficial research associated with alleviating problems caused by water and coming up with creative solutions. The Flood Resilient Group is a multidisciplinary research group affiliated to UNESCO-IHE and Delft University of Technology. It aims at advancing scientific knowledge and practical application into integrated approaches to cultivate resilience in urban communities and built-up areas to face uncertain climate and socio-economic drivers, as well as extreme floods. Activities on flood resilience, based on PhD research, deal with (i) quantifying impacts of changing drivers for urban flood risk, (ii) assessing restorative and adaptive resilience of urban flooding systems, and (iii) transition management and adaptive management for urban flooding systems.
Since the past 3 years, the Flood Resilience Group has been involved in a number of (about 10) finished and ongoing national and international projects, related to climate-proofing cities, urban flood management, and building precautionary measures. In the majority of these studies learning and research is implemented, together with local, regional, and national actors. Targeted cities include, among others, Dordrecht, Rotterdam, Haarlemmermeer, Hannover, Bergen, Sheffield (Europe), Achmedabad (India), Saint Louis (Senegal), and Porto Alegre (Brazil). This research resulted in a number of publications in peer-reviewed journals and in conference proceedings. Besides that the Flood Resilience Group contributed to the development of a new module on Flood Resilience for the Integrated Urban Engineering specialisation, to the Climate Adaptation Lab of the Delft University of Technology, as well as to a text book on Urban Flood Management.
The year 2007 marks a turning point in history: half of the world population now lives in cities (UN-Habitat, 2007). Moreover, the trend of rapid urban growth throughout the mid-20th century in the developed world has shifted to the transition and developing regions of Asia, Latin America and Africa. Urbanisation has led to an increase of economic and social wealth in some places, but also to continuing poverty of others. The total urban population is expected to double from two to four billion over the next 30 to 35 years (United Nations, 2006). These growth rates imply that, every week, a city of one million inhabitants will be built for the next four decades. An unwanted side effect of this process of rapid urbanization is the increased susceptibility towards flooding; the concentration of people and assets in flood prone areas has increased dramatically since many urbanized areas are located along major water bodies. Furthermore, climate change may cause floods to occur more frequent and severe. This combination is likely to result in substantially larger flood impacts compared to former times, in which societies developed more slowly and continuously adapted to environmental changes.
Historically, natural disasters were viewed as ´acts of God´, as disruptions to normality. Consequently, responses were directed towards managing floods as external events that affected an unknown and unprepared society. Major flood events in the past century, however, have acted as catalysts for changing policies towards floods. They have significantly increased our understanding and capacity to cope with floods. Yet, for the future significant revisions to our approach for managing urban flood risk will likely be necessary.
Inadequate urban planning
This lack of careful planning, or even uncontrolled urbanisation, will exacerbate the trend of increasing flood vulnerability of cities due to a combination of the following factors:(i) New ‘greenfield’ development in areas previously in non-urban use, leading to encroachment and expansion onto flood prone areas, such as flood plains and lowlands;(ii) Redevelopment of built-areas (‘brownfields’) and through ‘infill’ of the remaining open spaces in already built-up areas, leading to an overall density increase and subsequent increase of surface sealing and disruption of natural drainage channels;(iii) Urban areas once developed will rarely disappear and tend to favour the status quo, even after major flood disasters. The tabula rasa opportunity for correcting old errors and adopting new approaches to reduce vulnerability is seldom being exploited;(iv) Increased dependency on centralised infrastructure systems and utility services; Large, centralised systems generally have a greater technical complexity, are less adaptive, and exhibit greater impact from failure caused by floods than small, decentralised ones. A striking and recent example is the flooding experienced in the UK in 2007 which has caused the loss of piped water for 350,000 people for up to 17 days (Pitt, 2007).(v) Reduction in many safety margins due to improved modelling capabilities for prediction and optimisation. Consequently, cities are increasingly losing their capacity to adapt to fast changes and the ability to anticipate and deal with floods. These trends pose new challenges for urban flood management research and touch upon various disciplines (e.g. urban planning, regional economy, etc.). Because one cannot manage urban floods in isolation, there is a need for integrated approaches which address differing spatial scales, ranging from catchments to neighbourhoods. Furthermore, emphasis has to be put on the interactions across scale levels. We know very little about these interactions or how they might affect flood vulnerability of cities.
Climate change as a trend breaker
Past transitions in flood management policies generally existed of a process of predominantly incremental change, whilst reactive responses to flood disasters or narrow escapes have acted as catalysts for accelerating this process. An important notion is that current flood protection measurers are based on the accumulated knowledge of past weather events. Major flood disasters have created the need to shift from flood protection to a more integrated approach. In the last decade, however, climate change is recognized as a potential trend breaker, in the way that hydrological variables and existing statistical distributions of flood probabilities are affected. The present challenge seems to be that we must recognise that the future is inherently uncertain and that science will not necessarily reduce uncertainty. The long-term horizon of climate change and current scientific uncertainties pose special challenges. Strategies which address these challenges have in common that they recognize that there is no best solution, but they embrace future scenarios that fit a range of distributions of events that will not come as a surprise. In this sense, climate change provides new incentives for the need to plan ahead and to anticipate extreme events. A large number of studies show that we should start to adapt to climate change now, to prevent costly “emergency” interventions in the future. This means that flood risk management strategies must meet present needs, while providing an adjustment path for the future.
The Flood Resilience Group aims to advance scientific knowledge into integrated approaches to increase flood resilience of urban systems. The work focuses on the understanding of urban flood vulnerability and resilience and on the development and implementation of interventions and strategies that enhance urban flood resilience.
The research currently undertaken is focused along two research lines:
1. Impacts (and their changes over time) including dispersed (moderate) floods and extreme events confined to the urban context
2. Effective interventions and strategies to enhance urban flood resilience