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 ...
of
New Zealand. Its headwaters are the crater lake of
Mount Ruapehu on the
central plateau, and it flows into the
Tasman Sea eight kilometres southeast of
Whanganui. Due to the high acidity of the water coming from the crater lake, water is not diverted from the headwaters for the
Tongariro Power Scheme. Instead, it bypasses the Waihianoa Aqueduct via a ford.
Length
The river flows for southward to the
South Taranaki Bight near the settlement of
Whangaehu.
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. 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:
Tangiwai disaster
* 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
Tangiwai disaster.
Geology
The river is often poisoned with toxic chemicals from the volcanic activity in and around
Mount Ruapehu. 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
External links
* Horizons Regional Council
Whangaehu Freshwater Management Unit 2023
Rivers of Manawatū-Whanganui
Rivers of New Zealand
Tongariro National Park
{{ManawatuWanganui-river-stub