International audienceFlood exposure is increasing in coastal cities1, 2 owing to growing populations and assets, the changing climate3, and subsidence4, 5, 6. Here we provide a quantification of present and future flood losses in the 136 largest coastal cities. Using a new database of urban protection and different assumptions on adaptation, we account for existing and future flood defences. Average global flood losses in 2005 are estimated to be approximately US6 billion per year, increasing to US52 billion by 2050 with projected socio-economic change alone. With climate change and subsidence, present protection will need to be upgraded to avoid unacceptable losses of US1 trillion or more per year. Even if adaptation investments maintain constant flood probability, subsidence and sea-level rise will increase global flood losses to US60-63 billion per year in 2050. To maintain present flood risk, adaptation will need to reduce flood probabilities below present values. In this case, the magnitude of losses when floods do occur would increase, often by more than 50%, making it critical to also prepare for larger disasters than we experience today. The analysis identifies the cities that seem most vulnerable to these trends, that is, where the largest increase in losses can be expected

We compared the governance of flood risk in England and the Netherlands, focusing on the general policies, instruments used and underlying principles. Both physical and political environments are important in explaining how countries evolved towards very different rationales of resilience. Answering questions as ‘who decides’, ‘who should act’ and ‘who is responsible and liable for flood damage’ systematically, results in a quite fundamental difference in what resilience means, and how this affects the governance regime. In the Netherlands, there is nationwide collective regime with a technocracy based on the merit of water expertise, legitimated by a social contract of government being responsible and the general public accepting and supporting this. In England there also is a technocracy, but this is part of a general-political and economic-rational decision-making process, with responsibilities spread over state, insurance companies, individuals and communities. The rationales are connected to specific conceptions of the public interest, leading to specific governance principles. In both countries, flood risk strategies are discussed in the light of climate change effects, but resilience strategies show more persistence, although combined with gradual adaptation of practices on lower scales, than great transformations.

From a systems perspective, vulnerability can be defined as the relationship between a purposive system and its environment, where that environment varies over time. Which environmental perturbations are significant therefore depends upon the objectives of the system as only those perturbations that can inhibit the achievement of these objectives are significant. That system must decide whether to adjust in advance to each potential perturbation or to rely upon a recovery path when that perturbation occurs. In each case, it must then decide upon the adjustment or recovery path to adopt. In particular, the basic resources available to a household are time and energy where the rates at which these can be directly or indirectly, through earning income, converted to consumption are crucial. Perturbations can reduce the energy available as well as reduce the efficiencies with which time and energy can be converted to income.

Public or stakeholder participation in planning and management of natural resources is now widely practiced, but means different things in different contexts. Examples of recent participation in floodplain management in Bangladesh and England are reviewed in the national policy context. Participation in floodplain planning in England is influenced by a centralised state and European Union directives. The Ribble process tried to involve a wide range of stakeholders, but is limited to the development of plans through consultations structured and managed by the Environment Agency. By comparison in Bangladesh local participatory planning with different stakeholders has articulated their separate needs and suggestions, and brought them together to search for consensus. Decision making and responsibilities over flood management infrastructure and floodplain resources have been devolved to community organisations and co-management committees formed through the participation process. The Bangladesh examples show how participation can be made more accessible to people through events that have real local meaning since representatives gain power to raise funds and implement decisions for the benefit of their stakeholder constituencies. In Bangladesh rural populations dependent on floodplain resources have an incentive to participate in implementation and oversight of management decisions and actions that is lacking for most urban people in England. However, the merits of building up from local participation to catchment planning and of linking floodplain specific participatory institutions with existing local government are lessons that could be adapted from Bangladesh to England.

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