We will design a new multi-objective stochastic capacity expansion optimisation framework that considers economic criteria and other performance measures and explicitly evaluates the trade-offs between them. Optimal infrastructure ‘portfolios’ will be selected according to their performance across a range of measures (social, economic, engineered, ecological). In this new supply-demand planning paradigm single ‘optimal’ solutions will not exist, rather ensembles of optimal solutions will be offered, allowing decision-makers to assess trade-offs and select according to their preferences. All recommended infrastructure portfolios will be, in the language of multi-criteria decision-making, ‘non-dominated’, i.e. for each portfolio suggested by the approach, no further gains in any one objective can be achieved without simultaneously sacrificing performance in another objective.
‘Stochastic’ means the method will consider multiple sources of future uncertainty. For example in water planning this includes climate variations, hydrological inflows, changing water demands and energy prices. Planning that considers multiple sources of uncertainty helps select infrastructure portfolios that perform well under a wide range of future conditions. Such ‘no regret’ plans are ‘robust’ in the face of future uncertainty. Robustness, in this context, means that under many plausible futures the proposed plan will demonstrate high resilience (failure events of short duration), low vulnerability (small failure events), and high reliability (few failure events). Because the proposed planning framework is both multi-objective and stochastic, it will allow analysts to identify those portfolios which optimally trade-off between, for example, resilience and cost (or any other combination of objectives).
To demonstrate the general framework we will apply it to water and environmental planning in the Thames.