Decision Making under Severe Uncertainties for Flood Risk Management: a Case Study of Info-gap Robustness Analysis

Flood risk analysis is subject to uncertainties, often severe, which have the potential to undermine engineering decisions. This is particularly true in strategic planning, which requires appraisal over long periods of time. Traditional economic appraisal techniques largely ignore this uncertainty, preferring to use a precise measure of performance, which affords the possibility of unambiguously ranking options in order of preference. In this paper we describe an experimental application of information-gap theory, or info-gap for short to a flood risk management decision. Info-gap is a quantified non-probabilistic theory of robustness. It provides a means of examining the sensitivity of a decision to uncertainty. Rather than simply presenting a range of possible values of performance, info-gap explores how this range grows as uncertainty increases. This allows considerably greater opportunity for insight into the behaviour of our model of option performance. The information generated may be of use in improving the model, refining the options, or justifying the selection of one option over the others in the absence of an unambiguous rank order. Secondly, we demonstrate the possibility of exploring the value of waiting until improved knowledge becomes available by constructing options that explicitly model this possibility.