Severe Flooding in the Atoll Nations of Tuvalu and Kiribati Triggered by a Distant Tropical Cyclone Pam

Abstract

Tropical cyclone (TC) Pam formed in the central south Pacific in early March 2015. It reached a category 5 severity and made landfall or otherwise directly impacted several islands in Vanuatu, causing widespread damage and loss of life. It then moved along a southerly track between Fiji and New Caledonia, generating wind-waves of up to approximately 15 m, before exiting the region around March 15th. The resulting swell propagated throughout the central Pacific, causing flooding and damage to communities in Tuvalu, Kiribati and Wallis and Futuna, all over 1,000 km from TC Pam’s track. The severity of these remote impacts was not anticipated and poorly forecasted. In this study, we use a total water level (TWL) approach to estimate the climatological conditions and factors contributing to recorded impacts at islands in Tuvalu and Kiribati. At many of the islands, the estimated TWL associated with Pam was the largest within the ∼40-year period of available data, although not necessarily the largest in terms of estimated wave setup and runup; elevated regional sea-level also contributed to the TWL. The westerly wave direction likely contributed to the severity, as did the locally exceptional storm-swell event’s long duration; the overall timing and duration of the event was modulated by astronomical tides. The findings of this study give impetus to the development, implementation and/or improvement of early warning systems capable of predicting such reef-island flooding. They also have direct implications for more accurate regional flood hazard analyses in the context of a changing climate, which is crucial for informing adaptation policies for the atolls of the central Pacific.

Gauging mixed climate extreme value distributions in tropical cyclone regions

“…Future work could include the effect of waves on extreme sea levels for open ocean sandy beaches 39 – 41 and reef environments 42 along with the future nonstationary changes to EVD from global climate model projections 24 . Future work could also replace the sea level residual with skew surge analysis which could be recombined with tide using convolution methods 43 along with structural function approaches 41 to define extreme water level populations.…”

Coastal Wave Extremes around the Pacific and Their Remote Seasonal Connection to Climate Modes

“…For instance, Ranasinghe et al [45] and Anderson et al [46] observed shoreline rotation at embayed beaches, and Trombetta et al [47] observed an alongshore sediment drift reversal with large consequences for coastal zone management and infrastructures. These remote swells can also drive dramatic overtopping [6] even at storm-free areas, such as in the Gulf of Guinea [1,48], facing the South Atlantic storm track, and in the Pacific due to distant tropical cyclones [17,[49][50][51].…”

Estimating tropical cyclone-induced wind, waves, and surge: A general methodology based on representative tracks

“…For some locations, TCs making landfall nearby are most important (e.g., Charchenga), while for other locations extreme tracks passing at larger distance are equally important (e.g., Batticaloa). For example, TC generated swell waves have caused flooding at small islands in the Pacific over 1000 km away from the TC-track (Hoeke et al, 2020). In these environments, even for the SLMPS configuration, it is recommended to use a large selection domain that covers a wide range of tracks.…”