Predicting the unpredictable

Apr 17, 2013 by Sandy Evangelista
Credit: 2005 Brienz Creative Commons

(Phys.org) —EPFL scientists have developed the first system to issue early-warning alerts for landslides. Early-warning systems like this are already in place for other natural disasters such as tsunamis and tornadoes.

In a mountainous country like Switzerland, landslides are not uncommon. Unstable slopes cover about 6% of the country's total land area. And with global warming, these events are expected to occur more frequently. As precipitation increases and melt, more water will be flowing in the mountains; this could potentially trigger landslides in new areas.

John Eichenberger, a PhD student in EPFL's Soil Mechanics Laboratory, has spent four years under the direction of Professor Lyesse Laloui developing a tool that can reproduce the behavior of steep slopes when subject to heavy precipitation. Research was conducted in both the laboratory and the field, in particular on the slopes of the Rhine River, where he coupled sensors to a . The model was able to accurately detect when the saturation state of the soil reached dangerous levels, thus allowing an to be given.

These data provide a valuable source of information for protecting the population of a mountainous area such as Switzerland. The researchers also studied other regions in the world with very different soil types, such as the steep slopes of a volcano in Costa Rica.

The infiltration of water

It is very difficult to predict the intensity of a landslide. Experts generally categorize them as one of two types. There are the very deep slides that move slowly, on the order of several millimeters per year or per century. We are aware of them, and they're often monitored. "Depending on their speed, we can determine whether the situation is becoming critical, but even in these cases we don't know how to predict them," explains the scientist.

Then there are the surface slides, which are only a few meters deep. These slides are much more difficult to predict, and up to now, it was essentially impossible to anticipate them. They are unexpected and can move rapidly, from one to several meters per second. This is the problem Eichenberger decided to tackle. "In general, a steep slope remains stable via capillary effects, that is, thanks to suction between grains. This effect is lost when rainwater infiltrates the soil."

Inspired by tsunami warnings

How do you determine at what time an evacuation order should be given, knowing that it is not enough just to go by the weather forecast? This was the thesis subject launched by Lalouli, director of the Soil Mechanics Laboratory. "I was inspired by tsunami warning systems. They had to couple the deterministic model, which was based on physical mechanisms, with a probability model, based on a neural network. This is because other parameters, such as climatic variations, can complicate things. These are the data we don't know about."

From research project to case study

In 2009, the researchers saturated the slopes of the Rhine River with water at Rüdlingen. The soil was heavily instrumented with sensors for this field study of an artificially induced landslide. After 15 hours of , the slide began, at 3:00 am. One hundred and fifty cubic meters of soil slid into a protective net, validating the model.

The EPFL-developed early- for landslides is now being applied in Costa Rica, where the stability of Latin America's largest pozzolana mine, situated on the slopes of the Irazu volcano, is of critical importance.

In 2005, a mudslide flowed into the mine. Production was stopped, but there was no way of knowing when it would be safe to start it up again. Volcanic ash has particular characteristics, and samples were tested in the EPFL laboratory in order to adapt the model to the soil type.

The issue of land management

are closely tied to land management, and vice versa. Although are not regular occurrences in Switzerland, there are regions of the world, such as Hong Kong, where they are. And infrastructures cannot withstand natural forces indefinitely. "Our tool aids land management by precisely indicating danger zones," concludes Laloui.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: lms.epfl.ch/research/research-fields/environment/landslide-analysis-fr

add to favorites email to friend print save as pdf

Related Stories

MIT tool determines landslide risk in tropics

Jun 26, 2007

Engineers at MIT have devised a simple yet effective system for determining an area's landslide risk, a tool that could help planners improve building codes, determine zoning and strengthen mitigation measures in mountainous ...

Half of Indonesians at risk of landslides

Mar 28, 2013

More than half of Indonesia's population live in areas at risk of landslides, an official said Thursday, with traditional farming methods blamed for the widespread vulnerability.

New sensors to predict landslides

Apr 22, 2010

Researchers at the University of Southampton expect to have sensor probes which can predict the onset of landslides by the end of this year.

An accurate way of predicting landslides

Mar 13, 2013

A landslide can seriously injure or even kill people. Now, a new early warning system will be the first to employ geological data in tandem with the latest weather forecasts to provide a concrete warning ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Growing app industry has developers racing to keep up

Smartphone application developers say they are challenged by the glut of apps as well as the need to update their software to keep up with evolving phone technology, making creative pricing strategies essential to finding ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.