The 70th Anniversary of the Tangiwai Railway Disaster – A Volcanic Dam Break Story

Abstract

The Tangiwai Railway Disaster, which occurred on Christmas Eve in 1953, remains the most devastating rail accident in New Zealand's history. Of the 285 persons on board, 151 lost their lives when the train heading from Wellington to Auckland plunged into Whangaehu River shortly after the collapse of the Tangiwai railway bridge. The accident was caused by the break of a tephra dam, a natural dam formed by volcanic material, which held back Mount Ruapehu's crater lake. The resulting lahar, a fast-moving, mud-like flood, swept down the Whangaehu River, causing the destruction of the bridge's 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 become even more catastrophic. This article recounts the harrowing tale of the Tangiwai Railway Disaster, delves into the intricate and dynamic geomorphic and hydraulic processes that led to the dam's collapse, and examines the valuable lessons learned by New Zealand, including the implementation of an early warning system. Furthermore, as this case study focuses on the failure of a natural dam, the article also begins with a brief introduction to other types of significant natural dams such as landslide dams, avalanche dams, ice runs, and Glacial Lake Outburst Floods (GLOFs), to raise awareness among readers.