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8 October 2026/5 min read

Brienz: 62 weeks away from home and what monitoring costs

Brienz spent 62 weeks without its residents and runs a CHF 3.5 million monitoring programme. Why regions need a screening layer before site monitoring.

By Julian Walder

Brienz/Brinzauls, in the municipality of Albula/Alvra in Graubünden, is sliding. The whole slope beneath the village has been measured since 2009. What happened there between 2020 and 2026 is the clearest account in Switzerland of what it costs to watch a single unstable mountain closely, and of why that model cannot scale to a whole canton.

The slide

The monitoring programme at Brienz is the densest in the country. A Doppler rockfall radar on the access road went on trial in 2017 and into operation in 2018. An interferometric radar followed in April 2019, a high-resolution deformation camera in 2023, alongside GNSS stations, total stations, inclinometers, seismic sensors and periodic laser scans. Four systems feed 90 measurement points.

Those instruments recorded a slope that kept speeding up. In 2020 the fastest zone moved at 3 to 5 metres per year. By the end of 2022 it reached up to 20 metres per year. On 15 June 2023 about 1.2 million cubic metres came down as a debris flow, with local rates of more than 40 metres per day in the days before. The rail line through the valley, which the canton later named as infrastructure of national significance at risk, was closed that night. The village itself was moving at about 250 centimetres per year by autumn 2024.

62 weeks

On 17 November 2024 the village was cleared. Residents left their homes and the canton released CHF 500,000 in emergency aid. From May 2025 the canton moved to "phase orange", but residents could not yet return for good. A further debris flow came down at the end of November 2025. On 27 January 2026, after 62 weeks, the order was lifted and residents could move home. The period from November 2024 to November 2025 alone had cost about CHF 600,000.

The engineering response was a drainage tunnel of about 2 kilometres, begun in June 2024 and due for completion at the end of 2027. By August 2025 it had cut the village's motion from about 250 to well under 100 centimetres per year. The canton has also set aside CHF 50 million for voluntary relocation, and on 27 May 2026 the Federal Council asked parliament for CHF 18 million toward a Brienz resettlement.

What it costs to watch one slope

The monitoring system for 2025 to 2028 costs CHF 3.5 million, of which the canton pays up to CHF 2.8 million plus CHF 210,000; the commune operates it. That is about CHF 0.9 million per year, for one slope, before any protective works. By January 2023, about CHF 28 million had already gone into the exploration tunnel, monitoring and geology, with total protection estimated at CHF 68 million against a damage potential of CHF 177 million.

Kandersteg tells the same story in a different valley. Above the Bernese village the Spitze Stei rock mass, estimated at 16 to 20 million cubic metres, roughly twice the volume that fell at Blatten, has shown displacements of more than 7 metres in a year at single points and GNSS peaks of 70 centimetres per day. The eligible cost of monitoring, hazard basics and specialists is CHF 1,375,000 per year, CHF 5.5 million for 2025 to 2028, with the Confederation paying at least 35 percent, the canton most of the rest and the municipality 9.8 percent. Gross, the programme is about CHF 1.4 million per year, or 16 percent of a municipal budget of about CHF 8.8 million. Over CHF 11 million has been spent on preparedness. The cantonal decision authorising the credit states that no structural measure can reduce the hazard enough to allow monitoring to stop.

A single ground radar installation costs between some tens and some hundreds of thousands of francs; about 280 such installations exist worldwide. Graubünden spends about CHF 500,000 per year on general monitoring across the canton. Glarus budgeted CHF 2.9 million over four years.

The arithmetic of dozens of sites

These programmes are justified. Brienz and Kandersteg are known, large and directly above people. But a canton's problem is never one slope. The Valais hazard service monitors about 150 sites. Graubünden, Bern, Uri, Ticino and the others each carry their own lists, and Blatten was a reminder that the list is never complete.

Multiply the Brienz or Kandersteg figure, CHF 0.9 to 1.4 million per site and year, by a list of 150 sites and the result runs well above CHF 100 million a year for one canton. Switzerland as a whole spends about CHF 2.9 billion per year on protection against all natural hazards, and the federal commitment credit for avalanches, landslides and rockfall for 2025 to 2028 stands at CHF 161 million, with a further CHF 27 million requested in May 2026. Dense ground monitoring everywhere is not an option, and nobody is proposing it.

The question is not whether to watch every slope closely. It is how to decide which slopes to watch closely.

The layer before site monitoring

That is where regional screening belongs. Satellites already pass over every slope in a canton every few days. Processing that record into a per-slope motion history, detecting the onset of acceleration and ranking slopes by what lies below them answers the question the site programmes cannot: of the hundreds of slopes nobody is instrumenting, which three deserve a geologist's visit this month?

Watchberg is designed to be that layer. It does not reduce the need for radar at Brienz or Kandersteg; those slopes have earned their instruments. It aims to make sure the next Brienz is found while the numbers are still measured in centimetres per year rather than metres per day, so that the expensive instruments go where they are needed before, not after, the first debris flow. How early and how reliably it can do that is projected and to be validated in the pilot programme planned for 2027, with Brienz and Blatten as the reference back-tests.

Sources

  • Brienz
  • Kandersteg
  • Economics

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Pilot programme 2027. In discussion with hazard offices in three cantons.