Associated Press

A River Dammed by a Huge Swiss Landslide Is Flowing Again. That’s a Relief to Authorities

Keystone via AP
Check dams set up on the water from the Lonza river flows over the mud and stone, after the formation of a lake by the last houses of the village of Blatten, Switzerland, Saturday, May 31, 2025.

The Associated Press

10:43 JST, June 1, 2025

GENEVA (AP) — A small Alpine river dammed by a landslide that largely buried the Swiss village of Blatten is now flowing through the debris, and the level of a newly created lake that raised worries about potential new destruction has fallen, authorities said Saturday.

A huge mass of rock, ice and mud from the Birch glacier thundered into the Lötschental valley in southern Switzerland on Wednesday, destroying much of the village. Buildings that weren’t buried were submerged in a lake created by the small Lonza River, whose course was dammed by the mass of material.

Authorities worried that water pooling above the mass of rock and ice could lead to risks of its own. Still, the regional government in Valais canton (state) said that the Lonza has been flowing through the full length of the debris since Friday.

Geologist and regional official Raphaël Mayoraz said Saturday that the level of the lake has since gone down about 1 meter (3.3 feet).

“The speed at which this lake is emptying comes from the river eroding the deposit,” he said at a news conference. “This erosion is relatively slow, but that’s a good thing. If it is too fast, then there is instability in this channel, and that could lead to small slides of debris.”

“The Lonza appears to have found its way, but it too early to be able to give an all-clear,” said Matthias Bellwald, Blatten’s mayor.

The outlet of a dam downstream at Ferden, which is normally used to generate electricity, was opened partially on Friday evening to allow water to flow further down the valley and regulate the volume of water behind the dam. Authorities are still leaving open the possibility of evacuations further downstream if required, though the risk to other villages appears very low.

Days before most of the glacier collapsed, authorities had ordered the evacuation of about 300 people, as well as livestock, from Blatten. Switzerland’s president said on Friday that the government was looking for ways to help the evacuees.