Giétro glacier flood into the valley of Bagnes (1818)

In June 1818, a catastrophic lake outburst flood occurred in the Swiss Alps when the Giétro Glacier released a natural dam, sending water down the Dranse into the valley of Bagnes. The disaster killed 44 people, marking one of the worst events in the region's history.

Episodes

Background and detail

Background. The Giétro Glacier, located in the canton of Valais, experienced an increase during the 'Year Without a Summer,' leading to the formation of an ice cone in 1816. A lake formed behind this natural dam, measuring about 2 km in length by April 1818. Earlier, a similar lake emptied in May 1817 without fatalities, setting the stage for the subsequent disaster.

The Flood. The catastrophe is considered one of the worst disasters in Swiss Alpine history. The flood waters drained into the Dranse de Bagnes, a tributary of the Rhone. The event was particularly devastating for the municipality of Bagnes, which had previously suffered from floods in 1469 and 1595. The flood reached the village of Bagnes quickly, with alerts to Martigny coming too late.

Engineering Response. On 10 May 1818, the engineer Ignaz Venetz was called by the canton to address the situation. The flood reached the village of Bagnes ten minutes after the breach, and the alert was given to Martigny before 18:00, but too late. The event resulted in 44 deaths.

Sources

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