Strategic appraisal of flood risk management options over extended timescales: combining scenario analysis with optimization

Strategic flood risk management seeks to identify portfolios of flood risk management options that can be implemented in a staged and adaptive way. This raises substantial challenges from the point of view of risk analysis, two of which are addressed in this paper. First we examine the problem of dealing with scenarios of long term change and in particular socio-economic and climate changes. We build substantially on the scenarios approach adopted in the UK Foresight project and subsequent studies by introducing a quantified high resolution coupled econometric and land use simulator. This is used in an assessment of the combined effects of land use and climate change. Again against the background of climate change, we go on to address the complexity of constructing and analysing portfolios of intervention flood risk management systems. Specifically, we illustrate how a genetic algorithm can be used to search the very high dimensional option space of flood defence management options and sequences. This new integrated approach of scenario analysis and optimization is illustrated with examples from the Thames Estuary in the UK.