Probabilistic sustainability evaluation of hybrid breakwaters considering uncertainty in conceptualization and indicator weighting

Abstract

One of the distinguishing features of hybrid infrastructure is the need to find balance between multiple functional performances. Multi-criteria decision analysis is an ideal tool for exploring this balance and identifying an ideal solution, but there are few examples of its application to coastal infrastructure. This study conducted a probabilistic, multi-criteria decision analysis-based sustainability evaluation of hybrid breakwater structures considering two sources of methodological uncertainty: conceptualization and weighting. The target structures were evaluated by construction and maintenance costs, area of coral coverage, and embodied CO 2 emissions. In the analytical framework, uncertainty was propagated to the output of the evaluation, and exceedance probability was used to identify the “most sustainable” structural type. The Control+ATP structure – a conventional breakwater with the addition of an artificial tidepool – was the most sustainable alternative when considering both conceptualization and weighting uncertainties. It was also the least sensitive to methodological choices in the sustainability evaluation. On the other hand, the PB deep structure – a hybrid breakwater that integrates components to promote ecological development – had the highest environmental effectiveness but was highly sensitive to methodological uncertainties in the sustainability evaluation and was only ranked second or third overall. The evaluation results provide quantitative, empirical evidence of the multi-functional performance and sustainability of hybrid breakwaters. This study further demonstrated how to handle methodological uncertainties in sustainability evaluation by treating the output probabilistically, which is useful in the absence of an established decision-making framework. However, the trade-off between ecological performances should be explored in future studies.