Coastal hazard and risk assessment in The Marshall Islands

Published: 16 December 2016

The World Bank has approached Deltares for carrying out a hazard assessment for the two islands of Ebeye and Majuro and a relative coastal risk assessment for the island of Ebeye.

Projectleader Alessio Giardino about the project: “The hazards and consequent damages that those islands are facing are already extremely high. According to our estimates, annual expected damages in Ebeye may increase up to a factor three or four by 2100, depending on the sea level rise considered. The main issue is that feasible and sustainable solutions are also extremely costly and not always easy to justify based on standard cost-benefit analysis methodologies. One of the main challenges will be looking into roadmaps for long-term planning as well as possibility to reduce adaptation costs.”

Islands prone to the effects of natural hazards

The Republic of the Marshall Islands (RMI) consists of an atoll archipelago located in the central Pacific. The atolls and reef platforms are host to approximately 1,225 reef islands, which are characterised as low-lying with a mean elevation of 2 m above mean sea level.

The limited land size of these islands and the low-lying topographic elevation makes these islands prone to the effects of natural hazards. Moreover, the impact of those hazards is likely to increase dramatically in the future considering the effect of sea level rise and climate change. As generally observed, small islands have low adaptive capacity, and the adaptation costs are high relative to the gross domestic product (GDP).

Waves, storms surges, typhoons and tsunamis

The following hazards are analyzed as part of the study, using XBeach and Delft3D: waves, storm surges, typhoons and tsunamis. The direct consequences (inundation and coastal erosion) are evaluated specifically for the island of Ebeye. The analysis is carried out for different return periods and expected climate change scenarios and sea level rise. The hazard assessment is then used as a basis to carry out the coastal risk assessment, where information on hazards is combined with information on exposure and vulnerability.

Determination of weak spots where adaptation measures are required

The output from the risk assessment allows the determination of weak spots where adaptation measures are required at present or in the future and for which a conceptual design and cost-estimate is proposed. Also, the developed method allows testing the cost-effectiveness of each of these measures, in achieving the predefined objective in terms of risk reduction. This is a very effective strategy for reducing the total investment costs and maximizing the future benefits of the interventions.

stakeholders Marshall Islands

The results of the study have been discussed during several stakeholder consultation meetings in The Marshall islands and presented at the cabinet. The main outcomes from this work will form the basis of future World Bank projects on the islands.

Our contacts at the World Bank:

Nicolas Desramaut
Denis Jean-Jacques Jordy