Early warning system could predict landslides weeks in advance

The creators of a new landslide early-warning system claim it could help predict catastrophic events weeks or even months before they happen.

The technology could be as much as five times cheaper than existing methods and can operate continuously instead of only providing measurements every few weeks, say the researchers from two Munich universities who developed the system.

The alpEWAS (early warning system for Alpine slopes) uses a combination of underground cables and a surface-based video camera and laser scanner to detect and measure movement.

It also includes low-cost GPS antennas to measure surface movement and a piezometer for measuring the pressure of water in the ground, known as the water table.

Computer software then compares this information with data on previous ground movements to estimate how much activity is likely to take place in a certain time and to raise alerts if certain triggering factors occur.

Teams from the Technical University of Munich (TUM) and Bundeswehr University Munich (UniBW) have been testing the system, which cost €500,000 to develop, at a site in the Alps for over two years, gathering information about the soil movement.

‘We wanted to know how the triggering factors like rainfall and the build up of the water table influenced the velocity of the movement,’ TUM’s engineering geology chair professor, Kurosch Thuro, told The Engineer.

‘We’ve seen that when a large rainfall comes, like 60mm or more in 24 hours, we know that there is a build-up of the water table and the movement starts about two to three days after.

‘We expect that we would see a more catastrophic failure very early, maybe weeks or months before when something is changing in the slope. It normally starts with larger movements in a shorter timeframe, and we expect to be able to see that weeks beforehand.’

To detect ground movement, alpEWAS uses an underground co-axial cable similar to those used to connect TV aerials. The moving soil squeezes the cable and changes the electrical signal passing through it, which can be used to pinpoint and quantify the movement.

A video-tachometer measuring device is also used to detect surface movement at a distance of up to 200m depending on the air quality, complemented by a laser scanning device that provides additional data.

Thuro said the system needs to collect data for at least one summer and preferably over one year to build up an accurate picture of soil movement at any one site.

He added that the technology was more cost-effective than existing underground probes when used on larger sites that would require five to ten boreholes. ‘It’s not easy to predict but it could be up to five times cheaper than a traditional system.’

The alpEWAS team is working with several consultants at sites in Germany, Switzerland and Austria to install the system and is hoping to develop it for commercialisation.