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Managing flood risk, i.e. both the hazard and the potential consequences, is an important aspect of adapting to global change and has gained much traction in recent decades. As a result, a priori flood risk assessments have become an important part of flood management practices. Many methodologies have been set up, ranging from global risk assessments for the world as a whole, to local assessments for a particular stretch of a river/coast or small town. Most assessment frameworks generally follow a similar approach, but there are also notable differences between assessments at different spatial scales. This review article examines these differences, for instance those related to the methodology, use of assessments and uncertainties. From this review, future research needs are identified in order to improve flood risk assessments at different scales. At global/continental scale, there is a clear need for harmonised information on flood defences to improve assessments. Furthermore, inclusions of indirect economic effects at the macro-/meso-scale would give a better indication of the total effects of catastrophic flooding. At the meso-/micro-scale, there is an urgent need to improve our understanding of the effects of flooding on critical infrastructures, given their importance to society, the economy, emergency management and reconstruction. An overarching theme at all scales is the validation of flood risk assessments, which is often limited. More detailed post-disaster information would allow for improved calibration, validation and thus performance of flood risk models. Lastly, the link between spatial scales also deserves attention, for instance up- or downscaling methodologies. [ABSTRACT FROM AUTHOR]

Inner‐city pluvial flooding is characterised by major uncertainties, often making response problematic. We explore this in London, Lisbon, and Rotterdam, through ex post document analysis and semi‐structured interviews. Traditional uncertainty analysis generally focuses on quantifiable factors, needing to clarify uncertainty for engineering design, flood warnings and incident management. But other uncertainties concern budgets, skills, legal issues, and politics. There are also many relevant certainties or near‐certainties, which can dominate. They need equal attention in understanding decision making for risk reduction. Responses to our cities' flood risks—including portfolios of engineering and non‐structural measures—also contain significant no‐regret components requiring less certainty about risk. Our cities appear to be positioned along a learning continuum, related to flood experience and the consequential uncertainty reduction. However progress can be worryingly slow. Only experiencing actual flood events promotes accelerated action and often the certainties concerning resource constraints also outweigh the many uncertainties in risk assessment. [ABSTRACT FROM AUTHOR]

Because choice is conflict, decision-making is necessarily about conflict resolution. Choices are necessary because the options are mutually exclusive but the nature of this inherent conflict varies. Typically, these conflicts are multidimensional. In coastal zones, the complex interactions between systems makes decision-making particularly complex; in particular, environmental interests are themselves frequently in conflict. In making a choice, it is important to determine whythat choice is necessary in the first place. There are further conflicts about the objectives to be satisfied by the decision process; between the determination of the best outcome and the best decision process. Social scientists center upon the requirement for a fair decision process rather than upon seeking an optimum outcome. Unlike physical scientists who seek more and better information, social scientistsfocus upon the development and maintenance of institutions. [ABSTRACT FROM AUTHOR]