Climate change adaptation inherently entails investment decision-making under the high levels of uncertainty. Under these circumstances, the option of deferring a decision to adapt is one of possible strategies to address uncertainty. However, this decision will potentially leave people and areas exposed to the risk of coastal flooding during the deferral. In order to address this issue, a single fixed large investment can be divided into two or more sequential investments. This reduces the initial investment cost and adds flexibility about the size and timing of subsequent investment decisions as the magnitude of climate change becomes more available. This paper employs a real option analysis framework, as an analytical tool, to evaluate adaptations including flexibility to reduce both the risk and uncertainty of climate change, against increasing coastal flooding due to sea-level rise as an example. This paper considers (i) how to design the sequence of adaptation options under the growing risk of sea-level rise, and (ii) how to make the efficient use of flexibility included in adaptations for addressing uncertainty. This research incorporates a set of flexibilities (i.e. wait or future growth) into single-stage investments (i.e. raising coastal defence from 2.5 mAOD to 3.5mAOD or 4.0 mAOD) in two or three stages so that a set of multiple-stage adaptations are created to address both the risk and uncertainty of climate change. The proposed method compares the multiple-stage adaptations in economic terms, including optimisation, providing important additional information on the efficiency of flexible adaptation strategies given the uncertainty of climate change. The results from the analysis suggest that an efficient and robust strategy can be chosen for a short- and long- term adaptation.