Robust strategy for assessing the costs of urban drainage system designs under climate change scenarios

Abstract

Uncertainty inherent in precipitation predictions from general circulation model (GCMs) may lead urban drainage systems to be underdesigned (or overdesigned) in the future. This issue can be mitigated with the use of risk analysis models. In this study, a decision-making tool, developed based on six models (minimin, minimax, expected value, Hurwicz, Savage, and scenario-based multiobjective robust optimization), was used to select GCM/representative concentration pathways (RCP) scenarios that would lead to robust designs of an urban drainage system located in Fortaleza, Brazil. The implementation costs of the studied drainage system were estimated using runoff derived from rainfall predictions from six GCMs and two RCPs. After applying the proposed decision-making tool, three GCM/RCP scenarios were selected for yielding the most resilient and reliable designs. The range of feasible GCM/RCP scenarios reflects the level of optimism or pessimism held by a decision maker. We strongly recommend that this method be incorporated in urban drainage system design in order to help municipal planners make better decisions in view of climate change uncertainty.