Following the glacier's collapse, the sea is retreating.

In the Swiss canton of Valais, the threatening lake formed by the collapse of the Birch glacier on the dammed Lonza river is gradually draining. Residents and authorities are closely monitoring the weather forecast, with concerns growing about impending rain and melting ice.

Following the glacier collapse, the Lonza river is carving various channels through the massive debris cone that obstructs its bed. According to canton geologist Raphael Mayoraz, the lake behind the debris has decreased by one meter since the press conference in Ferden, Lötschental. Floating barriers have been installed to retain debris and prevent blockage of the outlet. The water volume has decreased from approximately one million cubic meters to around 800,000 cubic meters.

The slow drainage of the lake reduces the risk of the debris cone liquefying and releasing large amounts of material into the valley. This was a significant concern, as the unstable debris posed the risk of collapsing and further rock, ice, and rubble being washed downstream. However, the risk has decreased, according to Mayoraz.

Weather conditions could potentially destabilize the debris cone, increasing the risk of debris flows. In such an event, rock, rubble, and mud could move and slide down the valley, endangering communities further downstream. The melting ice and several days of rain forecasted for the region could contribute to this instability.

The debris cone itself remains highly unstable, with experts believing that one-third of the nine million cubic meters of material that ended up in the valley after the glacier collapse is likely to be ice. The exact timing of its melt or the potential formation of cavities within the cone that may cause it to collapse is unknown.

The cause of the disaster was the collapse of rock material from approximately 3,000-meter-high Kleine Nesthorn, which fell onto the Birsch glacier below. Under the weight, the glacier broke off last Wednesday and rushed into the valley with immense amounts of ice, rock, and rubble. The Kleine Nesthorn has not yet found its balance, and loose material remains at the collapse sites. This ongoing erosion of the mountain increases the risk of further rockslides.

Authorities are working to prepare for larger water or debris flows at the power plant in Ferden, about six kilometers downstream from the disaster area. The operator has partially emptied the reservoir to provide space, and the dam is reported to hold even under greater pressure. If a large amount of water collects there, the alarm will sound when the reservoir is two-thirds full. This gives residents of the communities of Gampel and Steg, near where the Lonza flows into the Rhone, enough time to evacuate.

The polluted water from the Lonza arriving at the dam in Ferden contains sand and debris from the landslide. Dredgers are operating in Gampel to deepen the drainage channels and address this issue.

Blatten, a village first mentioned in writing in the 15th century, has been almost completely buried under a meter-high layer of rubble at an altitude of around 1,500 meters. Even the church tower does not protrude. Most of the spared houses have been submerged in the stagnant water of the Lonza. The approximately 300 residents were evacuated to safety after the rockfalls. One local resident remains missing since the disaster.

The evacuated inhabitants have found accommodation elsewhere in the valley or with relatives. Many are taking advantage of the help of psychologists, with the Oberwallis Emergency Psychological Aid association reporting regular meetings. "Belief in a new Blatten has been planted," said Mayor Bellwald, who will soon present plans with a time horizon for rebuilding. "We don't need pessimism and bureaucracy, but practical solutions," he added.

The slow draining of the lake and ongoing instability in the debris cone pose multiple risks for communities in Blatten, Switzerland. Potential impacts include inundation of properties, infrastructure damage, displacement of residents, economic disruption, psychological and social effects, the risk of a dam break, and the threat of further secondary landslides. Emergency services and authorities are closely monitoring the evolving situation and responding with adaptive management strategies.

The environmental science community is closely watching the situation in Blatten, Switzerland, as the slow drainage of the lake formed by the collapse of the Birch glacier and the instability of the resulting debris cone pose multiple risks.
As climate-change continues to be a major concern, the potential impacts of such events, such as the threat of inundation of properties, infrastructure damage, displacement of residents, economic disruption, psychological and social effects, the risk of a dam break, and the threat of further secondary landslides, are of great interest to researchers in weather-forecasting, as they strive to predict and prepare for similar climate-related disasters.
In the field of environmental-science, professionals are working to understand the complex interactions between climate-change, weather patterns, and the delicate balance of ecosystems, like the one in Blatten, as events such as these highlight the urgent need for science-based solutions to protect communities and minimize the impacts of climate-change.