Effective coastal adaptation needs accurate hazard assessment: a case study in Port Resolution, Tanna Island Vanuatu

Abstract

Developing countries face risks from coastal hazards that are being amplified by climate change. The selection of effective adaptation interventions to manage these risks requires a sufficiently accurate assessment of the coastal hazard at a given location. Yet challenges remain in terms of understanding local coastal risks given the coarseness of global wave models and the paucity of locally scaled data in most developing countries, including Small Island Developing States (SIDS) like Vanuatu. This paper aims to examine the differences in hazard assessment and adaptation option selections arising from analyses using globally versus locally scaled data on coastal processes. As a case study, we focused on an eroding cliff face in Port Resolution on Tanna Island, Vanuatu, which is of concern to the local community and government authorities. The coastal process modeling revealed that the global wave data generated unrealistically high predictions of wave height within Port Resolution Bay. Expensive engineering adaptations designed to provide coastal protection were therefore likely to fail in preventing ongoing cliff erosion. In this case, the best adaptation solution involves changing land use to revegetate and help stabilize the cliff top. Our case study highlights the importance of accurate hazard assessment, especially in data-poor regions where the extrapolation of global datasets and models in the absence of local data can result in poor adaptation decision-making. Furthermore, the multidisciplinary approach applied here can be applied in other data-poor regions to strengthen analyses exploring the benefits of local adaptation interventions.

The Water-Food Equation in the Pacific

“…Data limitations for the Pacific region also limit down-scaled assessments of climate risk. For instance, Faivre et al (2022) completed a hazard assessment in Port Resolution Bay, Vanuatu and found very limited data of sufficiently high resolution to model coastal processes effectively, leading to the risk of recommending maladapted approaches. In this example available wave data generated unrealistically high predictions of wave height within the bay, which if taken on face value would lead to a recommendation for extensive and expensive engineering adaptation for coastal protection despite these solutions being likely to fail to prevent ongoing cliff erosion, even under worst case scenarios associated with a Category 5 tropical cyclone.…”

“…In this example available wave data generated unrealistically high predictions of wave height within the bay, which if taken on face value would lead to a recommendation for extensive and expensive engineering adaptation for coastal protection despite these solutions being likely to fail to prevent ongoing cliff erosion, even under worst case scenarios associated with a Category 5 tropical cyclone. The most appropriate intervention identified by Faivre et al (2022) was revegetation of clifftops to reduce erosion, a solution that may be lower in immediate and ongoing costs and come with numerous additional ecological and social co-benefits.…”