Characteristics of the 29th September 2009 South Pacific tsunami as observed at Niuatoputapu Island, Tonga

Niuatoputapu Island, Tonga, lies at the northern end of the Tongan trench, approximately 190 km east of the epicentre of the earthquake that produced the 29th September, 2009, South Pacific tsunami. The tsunami inundated 46% of the land area of Niuatoputapu, maximum inundation of 1100 m occurred along the southeastern coastline of the island while inundation distances in the villages were typically 200-500 m. Flow direction indicators show that the strongest flow of the tsunami came from a northeast to east direction; the tsunami refracted around the northern and southern points of the island and inundated the west coast from variable directions. Maximum runup of 4.7 m above mean sea level was recorded at the village of Falehau in the northwest of Niuatoputapu. The flow height of the tsunami reached a maximum of 16.9 m above mean sea level at Toma, on the southeast coast of Niuatoputapu. Flow heights were typically between 8 and 15 m along the eastern, uninhabited coastline of Niuatoputapu and decreased by about half, to between 4 and 7 m above mean sea level along the western, inhabited coastline. With no prior knowledge or education to prompt self-evacuation, its remote location hampering recovery efforts, and high tsunami flow heights, Niuatoputapu suffered severe tsunami impacts in the social, economic and physical realms. We discuss aspects of the tsunami impacts and the implications of the event on our understanding of South Pacific tsunami hazard and how tsunami hazards can be managed on small, remote islands.