Monitoring Skutshorn in Valdres

The unstable part of the mountain in Vang in Valdres moves by three centimetres a year. A tidal wave can take churches, schools, retirement homes and apartment blocks with it.

Skutshorn is the tenth mountain section in Norway to be put on continuous monitoring. Cautus Geo has instrumented and is involved in monitoring all of them. It is NVE that classifies unstable rock sections and initiates monitoring and is the client.

- We have established a total station that measures the 3D movement at 17 locations (points) in the unstable mountain section. In addition, we have three GNSS stations at Skutshorn. All the data has been analysed continuously over the past year and communicated directly to NVE," says Lars Krangnes of Cautus Geo.

Monitored since 2018

The instrumentation for continuous monitoring was put in place in the autumn of 2023, but the rock section with an unstable field of ten million cubic metres was already instrumented and monitored in 2018. This winter, the monitoring has been stepped up. There are several systems in operation. The aim is to ensure early warning if movements in the mountain section increase.

- Continuous monitoring has been implemented so that we can warn the population in good time before an avalanche occurs in the future," says Sverre Magnus Havig, head of the technical rock avalanche monitoring section at NVE.

If there is a risk of major rock slides, NVE will notify not only the municipality but also the police and the state administrator.

Stave church in danger area

Skutshorn is a large and unstable section of rock 600 metres above Lake Vangsmjøse. The decision to put the rock section on continuous monitoring was made in 2022. The instrumentation was put in place in autumn 2023. All the systems were quality assured, calibrated and tested in spring 2024.

A report from NGI has identified three specific areas that could be particularly affected by a tsunami if a major landslide is triggered. Most at risk is Øye in the western part of Vangsmjøse. There, large parts of the village will be affected. This also includes churches, including the Øye stave church.

The municipal centre at Grindaheim with its primary and secondary school, the Vangsheimen retirement home, the municipal building with doctor's office, residential buildings, campsite and the petrol station at Bøaflata are at risk. Calculations show that a tidal wave in Vangsmjøse could be up to 37 metres high.

European motorway under water

The E16 motorway, which is one of the main links between east and west, is at risk. NGI's flood report states that the E16 is more or less affected by all the hazard zones that have been investigated. The water masses will flood over the entire stretch from Vang primary and secondary school to the area where the old road towards Øye turns off the E16.

Large parts of the old road between Bjødndalen and Hemsing bridge are also affected.