CS5C - Concurrent Session 05C: The 70th Anniversary of the Tangiwai Railway Disaster – A volcanic dam break story

The worst rail disaster in the history of New Zealand happened on Christmas Eve, 1953, at 10:21pm. Of the 285 persons on board, 151 lost their lives when the train heading from Wellington to Auckland plunged into Whangaehu River. The Tangiwai railway bridge had collapsed just minutes the train arrival. The accident was caused by the break of the Tephra Dam, a natural dam formed by volcanic material, which was holding back Mount Ruapehu's crater lake. It released a lahar – a rapid moving, mud like flood - in the Whangaehu River. The lahar hit the Tangiwai railway bridge, washing away its piers and causing its beams and deck to fall into the river. The efforts of a passerby to warn the oncoming train kept this disaster from being even worse. This article will tell the story of this disaster, what led to it, how it happened, who was involved, and the lessons learned by New Zealand, including the installation of an early warning system. We propose to present a 10min video documentary for the conference session. Since this case study is about the failure of a natural dam, for awareness, the article will briefly acquaint the reader with the other types of large natural dams such as landslide dams, avalanche dams, ice runs, and Glacial Lake Outburst Floods (GLOFs).