Inundation of a low-lying urban atoll island: Majuro, Marshall Islands

Majuro is a low-lying island perched on a coral atoll in the central Pacific Ocean and is home to nearly 28,000 people. Considered highly vulnerable to the impacts of marine inundation, Majuro is expected to experience increasingly severe inundation as a result of continued sea-level rise. Popular media, academic papers, government reports, disaster declarations and other online resources are used to document 18 inundation events at Majuro over the past 36 years, which caused considerable impact to local physical and anthropogenic systems. The physical drivers and impacts of the documented inundation events are examined using tide gauge and weather observations and wave model hindcasts. The ocean-facing shorelines of Majuro experience frequent inundation caused by swell waves generated by distant storms from both the north and the south Pacific Ocean. In some instances, complete overwashing of the island by swell waves has been reported. Less frequent, although potentially far more damaging, are inundation events associated with typhoons and tropical storms, with the most recent in 1997. Inundation along the sheltered lagoon-facing shoreline of Majuro has occurred in the absence of waves due to the coincidence of high sea levels during La Niña conditions and seasonally high tides, as in 2011. Lagoon inundation also appears to have been caused by offshore swell penetrating into the lagoon, most effectively at high tide, and by locally generated wind waves within the lagoon. The classes of inundation identified in this study have unique drivers and the impacts have varying spatial and temporal characteristics in terms of impact and predictability. The inundation events are discussed with respect to the drivers of inundation and the future outlook under rising sea-level conditions.