A decision analysis approach to climate adaptation: a structured method to consider multiple options

Decision-making for climate adaptation operates in an uncertain environment. Formal processes to decision-making under uncertainty weigh the ability of a decision rule to achieve multiple and sometimes conflicting objectives in an evaluation procedure. Increasingly, computer simulation models are being applied for this reason, so that the effectiveness of decisions can be evaluated before actually implementing them in reality. In this paper, we develop a simple stochastic simulation model of beach recession under climate change in Australia and evaluate decision rules for beach replenishment in the context of three management objectives: (i) to reduce beach recession, (ii) reduce variation in beach recession, and (iii) do so cost-effectively. Results indicate that a decision to intervene and replenish the beach based on a trigger level would be effective at maintaining shoreline position, with relatively little variation, but did so at a relatively high cost of multiple interventions. A decision procedure to intervene at a fixed period resulted in greater shoreline position variation but constrained management efforts and costs. This structured approach offers an evidence-based process to decision-making that lays bare the assumptions upon which decisions are made. This, in turn, allows for a more complete analysis of all the uncertainties and better outcomes.