Rauma in the west Norwegian region of Romsdalen was the centre of national attention last autumn following a landslide prediction. Nothing happened, but the man who sounded the alarm stresses that it was right to warn of the risk.

Head geologist Lars Harald Blikra at the Åknes/Tafjord Monitoring Centre – now part of the Norwegian Water Resources and Energy Directorate (NVE) – was keeping a continuous eye on one of Norway’s four high-risk mountain regions.

Such big movements had been measured in Mount Mannen during the autumn that part of it looked likely to collapse. Eleven residents from nearby farms were evacuated on 22 October, and the Rauma railway line was closed.

The mountain was the big topic of conversation in Norway for the following week, with everyone asking when the big landslide would happen.

Hordes of journalists descended on the area, cameras were installed for live broadcasts, and the whole population followed developments on tenterhooks.

The landslide was imminent, according to Blikra, who produced daily analyses, forecasts and assessments of acceleration phases.

Meanwhile, it continued to rain, civil defence forces were mobilised, justice and public security minister Anders Anundsen visited the evacuees ­– and the press was ready to report the latest news.

The tension peaked on 28 October. With displacements in the mountainside of up to seven centimetres per day and more rain expected, the predictions were sufficiently unambiguous for Blikra to forecast an avalanche that day or the following night.

But then the rain ceased, temperatures fell below freezing and the rock stabilised. No landslide occurred.

With the drama over, the journalists packed up their cameras and left the area. By 3 December, the mountain was stable enough for the evacuees to return home.

Council chair Lars Olav Hustad in Rauma local authority (left) briefs Anders Anundsen, minister of justice and public security, on the status of Mount Mannen. Its condition was the big topic of conversation in Norway last autumn – with a huge media presence and nail-biting live transmissions. (Photo: Terje Pedersen/NTB Scanpix)

Questions

This event poses several questions. How did Blikra feel about appearing on TV and promising a accident which never happened. And were the scientists exaggerating the threat?

Blikra himself became a national celebrity overnight, but took the commotion very calmly. “I haven’t given this much thought afterwards. It’s just the way things turned out.

“This was straightforward enough in itself. People were evacuated, and our job was to communicate developments on the mountain.

“The crisis management team, which comprised the local authority and the police as well as us, agreed that we had to be honest about the forecast. But we could only report what we knew.”

He emphasises that securing the confidence of the general public is an important part of this information process, particularly with regard to the evacuees.

So it was important to be accessible to and clear in the media, but Blikra feels that the big press presence meant that things became a bit exaggerated and sensationalised.

“We felt under a little pressure towards the end to put a date on the landslide. At the same time, I think we managed to restrain ourselves and concentrate on what we actually knew.

“There was a natural desire, particularly on the part of the evacuees, for the rockfall to happen. That would have been the end of it. Everyone was hoping for this, so we didn’t regard stabilisation of the mountain as a good outcome.”

Warning

Blikra understands why the affair attracted such attention, because this was the first time in Norway that a landslide warning had been issued in this way.

Getting live coverage of an avalanche was a news story in itself. And evacuating residents underlined the seriousness of the position.

The geologist emphasises that it was imperative to issue a warning. “Although much is uncertain, the precautionary principle must be observed.

“Things don’t always turn out the way you expect, but we can’t afford to wait and see. The consequences of delay could be too great.

“At the same time, such alerts must be as realistic as possible. We can’t constantly issue warnings – our forecasts must be based on what we know.

“Uncertainty can’t be allowed to prevail if we’re to give clear advice on hazards to society and the police. Things must be sufficiently specific for a choice to be possible.”

Long days

Daily press conferences took place in the last week of October – and everyone wanted a piece of Blikra. It was a case of long days with little rest.

The whole geological team, which worked a 24-hour duty rota, found itself under strong pressure. They learned lesson from that.

Better organisation of the duty roster and improved media management will be needed next time – and there will certainly be another round sooner or later.

Blikra is convinced that Mannen will not remain standing for eternity. But when part of the mountain might collapse, and how large such a slide could be, are more difficult to predict.

“Given what we know now, we’re likely to get another period of movement in the rock,” he notes. “But such cycles could continue for a number of years before the rock is so weak it collapses.

“In other words, it’s not certain that an avalanche will occur this year either. That brings us back to the question of uncertainty.

“We don’t know what the rock looks like internally – how weak it is and what’s needed to get it moving. All we can do is look at the measurements. For now, we can’t do much more than wait.”

He says that the only option if the analyses show renewed acceleration at similar speeds as before is to notify the police and local council, who are responsible for evacuation.

Solutions

Explosives and water-bombing represented possible solutions when Mannen was creaking at its worst last autumn, so the question is why the problem area was not simply blasted away.

“Such human interventions can create even greater uncertainty,” Blikra notes. “It’s not given that this would have had the desired effect. On the contrary, an even bigger landslide could have been unleashed – and caused more serious damage.”

That is because only about 120 000 cubic metres of the mountain began moving last autumn, while the whole unstable rock formation totals 15-20 million cubic metres.

This explains why Mannen is a high-risk area under round-the-clock observation. The other three in Norway are Åkneset and Hegguraksla in Møre og Romsdal county and Nordnesfjellet further north in Troms.

Several independent systems are used to ensure stable and continuous monitoring of these regions, including GPS, ground-based radar, tensiometers, lasers, geophones and angle gauges.

Combined with measuring motion, water table and temperature in deep boreholes, this allows the geologists to register changes in the movement of the mountain slopes and issue timely warnings.

Rauma, 29 October 2014: the temperature has dropped and snow fallen on Mount Mannen overnight. The mountain has stabilised – for the moment. (Photo: Terje Pedersen/NTB Scanpix)

Landslides in Norway

Norway’s biggest prehistoric collapse of a substantial volume of rock amounted to several hundred million cubic metres, while Tjellefonna on the Romsdal Fjord was the largest recorded slide.

Totalling 15 million cubic metres, that event occurred in 1756. In more recent times, the Ta Fjord slide in 1934 involved three million cubic metres.

Big landslides are rare, with two or three incidents per century in Norway. The northern part of the west coast has been hardest hit.

In addition to the Ta Fjord event, Loen was affected by large avalanches in 1905 and 1936. A total of 175 people died in the three incidents.

Characteristically, the probability of future slides is low but their consequences can be very substantial in the form of wide direct devastation and extensive flooding.

The development of settlements and other infrastructure along Norway’s fjords and growing tourism mean that society has gradually become more vulnerable to such events.

Experience from Norway and other mountain areas shows that warnings almost always precede big landslides in the form of creep in the slopes. These findings form the basis for emergency preparedness against avalanches.

Source: Åknes/Tafjord Monitoring Centre