UN REPORTAGE EN SUISSE DE SARKER SAQIB (DHAKA TRIBUNE).
Scientists fear that continued warming of permafrost can lead to more frequent and disastrous rockfalls and mudslides, endangering communities living in the valleys in the Swiss Alps
With rainfalls and storms getting more intense than before disaster management work in the Swiss Alps is getting harder. It is also more challenging because there are more people living in the valleys, where villages are susceptible to rockfalls and mudslides from above. The increasing frequency in stronger rain and storms makes the work of preventing damage from natural disasters much harder for people like Raphael Mayoraz, who is in charge of the forest, river and landscape services office at Canton Valais. His office is under the Department of Mobility, Territory, and the Environment (Département de la mobilité, du territoire et de l’environnement). Mayoraz says that rockfall events increased significantly in 2018 compared to previous years, with about 400 events recorded just in January, which is more than double the amount of rockfalls in the whole of 2017.
House to the famous Matterhorn, Canton Valais is situated on southwestern part of the country and it is the most Alpine laden canton in Switzerland. The 5,224 square kilometre canton has a population of 339 thousand.
Tasked with the job of making sure casualties to life and properties are minimized, Mayoraz works with a group of engineers to take care of natural hazards in the canton. “We have the highest peaks in Switzerland. Local population is about 350 thousand people. And we are actually 18 engineers to take care of that. This includes hydrological or river provinces and all other geological areas, including seismic provinces. But we mostly deal with rock falls, debris flows, landslides and avalanches,” Mayoraz said.
As part of the prevention work Mayoraz and his team create natural hazard maps using data from the field and set up alarm systems. “The alarm system basically tells us that ‘this is moving fast’ or ‘that is moving but not very fast’,” he said. This data is combined with weather forecast to predict events and take preventative measures. “Very often we place surveillance systems to see how the terrain moves. We set up webcams and all sorts of equipments that feed to here in our computers. This enables us to carry out the management work,” he added.
The increase of movements up in the mountains is mainly due to increase in rainfall intensity, says Mayoraz. “In a regular year like in 2016 or 17 we just had 150 events. But we got about 400 events just in January this year. This is because of lot of rain,” Mayoraz said.
He observes that the rainfalls are not necessarily more than before, rather they are more intense. “More intense rainfall. is the reason for increased risk. I mean if you summarize the old rain during the year it’s about the same. It’s just that we are possibly getting more frequent rain, but higher intensities. 20cm in this area is quite a lot. It’s very difficult to contain and manage,” he said.
There are also a lot of avalanches at the same time higher in the mountains. However, a lot of those don’t end up affecting people living down in the valleys. “About 95 percent of those avalanches don’t affect people, because they are really high in the mountain and only animals are exposed to them,” he added.
Moving mountains by messing with the permafrost
One of the key contributing factors to the increase in movement up on the mountains is attributed to the warming up of permafrost, which causes, among other things, mountains to move.
Permafrost is essentially permanently frozen ground. If it thaws, there is a risk of natural hazards like rockfalls or debris flows, as it works like a glue that holds big parts of mountains together. The temperature of permafrost is permanently below 0°C. Permafrost covers some five percent of Switzerland’s territory. Retaining the ‘permafrost state’ is more directly linked to ground surface temperature than air temperature. Permafrost is mainly found at elevations above 2,500 metres.
“The permafrost basically cements big blocks of rock together that form the mountains. Naturally, enormous pressure is being exerted on the ice. The rock basically becomes like the sledge of a skier and glides on the ice when warmer temperature (close to zero) makes it more impressionable or softer,” said Reynald Delaloye, Professor in Physical Geography at the University of Fribourg.
The warming up of the permafrost, which is holding the highest peaks in place in the Alps, threatens natural calamities like rockfalls, flash floods and mudslides. Prof Delaloye, who works mainly on permafrost monitoring, its evolution over time and all processes related to that, says if temperature stays below zero then there is no threat to stability.
“If the temperature of the ice is sufficiently cold, at -5 for instance, then there is no water there. If the ice is really cold it is stable. But as it warms up it becomes susceptible to the extreme pressure from the mountain,” he said.
Prof Delaloye points out that the critical juncture is not really at permafrost completely disappearing, but when it comes close to a zero degree. The more imminent threat is permafrost coming close to a zero degree, thus creating a lot of water in the permanently frozen ground, which unstick the big rocks that form big parts of mountains.
“If the ice is at a temperature close to zero, at -0.5 to -.20, then that is still frozen state but you will have a lot of water because of the pressure,” said Prof Delaloye.
Dr Marcia Phillips, Team leader of the ‘Snow and Permafrost’ and ‘Permafrost and Snow Climatology’ teams at the WSL Institute for Snow and Avalanche Research SLF at Flüelastrasse Davos Dorf, says that it is difficult to determine pattern in geography without having extensive data over a long period of time. It becomes even more challenging for permafrost, which is a relatively new field of study and does not have extensive record, compared many other geological phenomenon. However, Dr Phillips says that even though it is hard to discern patterns, there is clear evidence of warming.
“We can say that we have cooling periods, but we have mainly warming. We can see it. We are measuring warming. It’s not that easy to measure. Sometimes our instruments show warming even though there isn’t one, which can be an electronic problem. You have to be very careful how you interpret the data,” she said.
But the data that has been determined as accurate shows what it looks like in the ground. “In 10 and 20 metres depth you can see there is warming,” said Dr Phillips.
At the SLF institute, where Dr Phillips run a monitoring network for monitoring permafrost in the Swiss Alps, her team set up boreholes in different terrains to measure changes in permafrost. The SLF team under Dr Phillips set up boreholes in the rock up at the top of the mountain, in ice-rich permafrost, and also in between in steep slopes.
“From our measurements we can see that permafrost is getting warmer,” said Dr Phillips. “Permafrost is cold, it ranges between -3 and -7. But it’s getting warm. The rock glacier, which have lots of ice in them, they react much more slowly. Because they have reached just below zero. But you need a lot of energy to transform that into water,” she added.
Rock glaciers are really fast and they are a problem for the villagers down below. “When it’s too steep then the front material can go down with rainfall for example. You either get a mudflow or debris flow. This is very destructive if you have a village below,” Dr Phillips said.
Erratic weather and an environment placed with instability
Like the rest of Europe, there have been a large number of heatwaves in summer in the Swiss Alps. There is also long dry periods and then really intense rain falls. “This is a problem. It’s definitely affecting high mountain areas,” said Dr Phillips.
Because of snow on top, the heat from the air cannot transmit directly to permafrost. “The snow acts as a buffer,” Dr Phillips explained. But as the snow melts and leave the surface unprotected, the top of the mountain becomes less stable.
“There are movements on the ground, because we are on slopes. Rock glaciers move because they have ice in them. And we have been seeing massive acceleration in the rock glaciers, except for the last two years and it slowed down again. It tells us that the cooling has an affect on the dynamics of these features. We think when it’s really hot the water can penetrate the rock better. And water is what making these things move,” Dr Phillips said.
And the effects of these changes are clearly seen by Raphael Mayoraz. “Higher in mountain permafrost is melting. That is producing a lot of unstable rocks, gravels and sand that are ready to go down in debris flow in the valley when you have very bad weather and lot of rain and storms. Especially in the summer when you have local storms that sustain for as long as an hour. It produces a lot of water in the same place and that creates debris flow that can go all the way down to the valley,” said Mayoraz.
The last few years have been particularly difficult for Mayoraz and his team as very intense local storms continue to rage in the region. Weather forecasts, while helpful, cannot predict the exact path of a storm. “On top of that if the storms move then the path becomes very difficult to predict. Like last year there was a very good prediction for a storm following the Southern part of the Rhone Valley. And it was moving very fast at 70km per hour. It originally headed to the North but it ended up hitting the South. And it was so fast that it was impossible to call local people and warn them, because we had about a ten minute window before it started pouring down,” Mayoraz recalled.
Power through prevention
While the global climate change continues to cause erratic weather, and consequently instability in the Alps along with all other regions, the contingency plan for disaster management primary comes in the form of better prevention systems. This includes building dams, fences and stopping big avalanches by triggering artificial avalanches by explosives. Mayoraz’s team has been successfully preventing disasters through all of these means.
“There is a village in the valley to Zermatt where there has been a lot of debris flow because there is a block of rock glacier on top. And we have been able to create a dam that collects all the debris flow and we can take it out with machines later. This village is relatively well-protected now,” he said.
Early warning system is also a key tool in preventing damages. Technologies like satellite images and radar measurements are used to observe and take actions by Mayoraz and his team or engineers. “We can usually detect with satellite or radar measurements that a major part of a mountain is starting to move. And if there is a village bellow we might have to evacuate that,” said Mayoraz.
“We had such a movement in an area close to the Great Aletsch Glacier,” he continued. “Millions of cubic metres of rock was moving at a very fast speed, in geological speed. One metre a day is very fast in geological terms. But in this case luckily there wasn’t any village below, so we didn’t have to evacuate,” he recalled.
Aside from effective early warning systems, intervention is also important, Mayoraz points out. “There are various things that we can do. For instance, if we see a big rock is moving, given it’s not too big, we can explode it,” he said.
For avalanche, Mayoraz’s organization – Service cantonal des forêts, des cours d’eau et du paysage (the forest, river and landscape services office) – has been constructing thousands of kilometre of fences that are holding the snow up in the slopes. It also regularly trigger explosions and prevent big avalanches. “If you wait, a slab can build up to 4 metres of snow, which can be a disaster when an avalanche starts from that. But for every half metre of snow you can impose an avalanche by blowing it up through controlled explosion. It creates a small avalanche which does not cause a natural disaster,” explained Mayoraz.
His team does this almost every time after a snow storm. There are designated stations where explosions are carried out, using small 2.5kg bombs.
“We also do mathematical simulations to make natural hazard maps. This helps us prevent people from building chalets in risky areas. Because of advances in technologies these simulations are getting better,” Mayoraz said.
For managing rockfalls, the computers are are helping predict major events. “This enables us to actually regulate where people can build chalets and prepare clear instructions,” said Mayoraz.
The organization also builds dams at the bottom of mountains. These are right at the outskirt of a village to catch debris flow. “We spend about 30 million Swiss Franc per year for all these structures (dams and fences),” Mayoraz informed.
Mayoraz’s office interact with its counterparts in other cantons. All 26 cantons in the country have organizations for natural hazards. “We also interact with foreign countries, with the French in Chamonix and with Aosta Valley in Italy. These are similar regions. We exchange information about satellite measurements and matters like that,” Mayoraz said.