The Whangaehu River is a large river in central

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. Its headwaters are the crater lake of

Mount Ruapehu Mount Ruapehu (; ) is an active stratovolcano at the southern end of the Taupō Volcanic Zone and North Island volcanic plateau in New Zealand. It is northeast of Ohakune and southwest of the southern shore of Lake Taupō, within the Tongari ...

on the central plateau, and it flows into the

Tasman Sea The Tasman Sea (Māori: ''Te Tai-o-Rēhua'', ) is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand. It measures about across and about from north to south. The sea was named after the Dutch explorer Abe ...

eight kilometres southeast of

Whanganui Whanganui (; ), also spelled Wanganui, is a city in the Manawatū-Whanganui region of New Zealand. The city is located on the west coast of the North Island at the mouth of the Whanganui River, New Zealand's longest navigable waterway. Whangan ...

. Water is diverted from the headwaters for the

Tongariro Power Scheme The Tongariro Power Scheme is a 360 MW hydroelectricity scheme in the central North Island of New Zealand. The scheme is currently operated by electricity generation company Genesis Energy. The scheme takes water from tributaries of the Rangit ...

Length

The river flows for southward to the

South Taranaki Bight The South Taranaki Bight is a large bay on the west coast of New Zealand, south of Taranaki, west of the Manawatu, north and west of the western entrance of Cook Strait and north of the South Island. The name is sometimes used for a much smaller ...

near the settlement of

Whangaehu Whangaehu is a settlement in the Rangitikei District and Manawatū-Whanganui region of New Zealand's North Island. Whangaehu is located near the mouth of the Whangaehu River, a large river flowing from for the crater lake of Mount Ruapehu o ...

Notoriety

The sudden collapse of part of the Ruapehu crater wall on 24 December 1953 led to New Zealand's worst railway accident, the

Tangiwai disaster The Tangiwai disaster occurred at 10:21 p.m. on 24 December 1953 when a railway bridge over the Whangaehu River collapsed beneath an express passenger train at Tangiwai, North Island, New Zealand. The locomotive and the first six carriages ...

. A

lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...

– a sudden surge of mud-laden water – swept down the river, significantly weakening the structure of a railway bridge at the small settlement of Tangiwai. The overnight express train between Wellington and Auckland passed over the bridge minutes later, causing it to collapse into the turbulent waters. Of the 285 people on the train, 151 were killed.

Timeline

* 13 December 1859: The bridge was washed away. * In February 1862

James Coutts Crawford James Coutts Crawford (20 July 1760 – 10 May 1828) was an officer in the Royal Navy who served during the American War of Independence and the French Revolutionary and Napoleonic Wars. Crawford first went to sea aboard merchant vessel ...

was given a number of old songs and "various accounts of the taniwha, one of whom we were told overthrew the Wangaehu bridge." * 1889: flood caused by the eruptions of Ruapehu. * 1895: flood caused by the eruptions of Ruapehu. * 24 December 1953:

* 18 March 2007: Mt Ruapehu crater lake bursts sending an estimated 1.29 billion cubic metres of water, mud, and sludge. The Ruapehu

ERLAWS The Eastern Ruapehu Lahar Alarm and Warning System (ERLAWS) is a lahar warning system that was installed on Mount Ruapehu, New Zealand following volcanic eruptions in 1995–1996. The system successfully detected and warned of an imminent lahar ...

alarm successfully activated preventing any accidents. This

Lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...

was 50% bigger than the 1953 Lahar that caused the

Geology

The river is often poisoned with toxic chemicals from the volcanic activity in and around

. The upper part of the river begins as the melt water from a small glacier. When hot water from the lake spills, it quickly melts the ice and snow in the glacier forming a cave-like tunnel when viewed from below.

Notes

Rivers of Manawatū-Whanganui Rivers of New Zealand {{ManawatuWanganui-river-stub