The 1818 Giétro Glacier catastrophe , killing 44 people , originated in a 4-km long valley located in south-western Switzerland . Fatal flooding was known during historical times with 140 deaths first recorded in 1595 . After an increase of the glacier during the " Year Without a Summer " , an ice cone started to form from the accumulation of falling seracs . During 1816 , the valley filled into a lake which emptied during the spring of 1817 . In spring of 1818 , the lake measured about 2 km in length . To stop the rapid rise of waters , the canton engineer Ignaz Venetz decided to drill a sluice hole through the ice , tunneling from both upstream and downstream sides of the ice dam at an elevation of about 20 metres above the lake surface . An avalanche interrupted work , so a secondary tunnel was then drilled for safety reasons as the waters rose to 10 metres below . Dangerous sloughing of ice delayed the work until finally a 198-metre-long hole was completed on 4 June , days before lake began to escape via the manmade waterfall on 13 June . Venetz warned the inhabitants of the valley of the danger as water was also escaping from the base of the cone . However , the cone began to crack on the morning of 16 June and at 16:30 the ice dam broke sending 18 million m3 of flood waters into the valley below
Year Without a Summer
Year Without a Summer
Glacial lake outburst flood