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[MANILA] A low-cost sensor that can detect landslides has been developed in the Philippines and is being promoted as an alternative to expensive early warning systems manufactured overseas.

The sensor costs less than US$1,000, in contrast to standard commercially available landslide sensors that can cost up to US$60,000 — excluding installation costs.

The Philippine system was developed through collaboration between the National Institute of Geological Studies (NIGS) and the Electrical and Electronics Engineering Institute, both part of the University of the Philippines.

Two prototype sensors were deployed 14 months ago in the upland province of Benguet, selected by the researchers because of its high vulnerability to landslides.

The sensor uses power available from an electric grid, but has a back-up battery in case of power failure.

"The sensor is buried vertically in the bedrock of the areas that are being monitored for possible landslides," explained engineer and programme leader Joel Joseph Marciano Jr. 

The sensor logs ground movement electronically and transmits a report every ten seconds to the NIGS, which serves as a central base station. Geologists then process and analyse the data, measuring various parameters that affect the sturdiness of slopes, such as rainfall intensity and moisture content.

Sandra Catane, a NIGS geologist, said her team has already noted a displacement of 20 centimetres in Puguis, Benguet, since the sensors were deployed.

But she admitted that, at present, they still have to identify the tipping point that indicates when a landslide is about to occur.

According to Catane, the project was initiated following a landslide in Southern Leyte in 2006 that buried the village of Guinsaugon, killing more than 1,100 people.

"It was an experience that can occur in one in 1,000 cases, and [was] an eye-opener for us," she said.

Landslides occur because of loosened soil and rocks. Strong rains are the most common cause of landslides in the Philippines, although ground movement — for example, resulting from an earthquake — can increase the probability of a landslide occurring.

Catane said the eventual widespread deployment of the landslide sensors is also an opportunity to create a database on landslides in the country, and could trigger an interest in this area of geology.

But the project faces several problems, including the lack of trained geologists to carry out reconnaissance and choose the appropriate area for deployment of the sensors; interpret the results; and make a visual validation after the data has been logged.

Catane added that the copper wires attached to the deeply-buried sensors had already been stolen twice, apparently to be sold as scrap metal. She emphasised the need to make communities aware of the importance of sensors, and to train them to manage and secure sensors for their own safety.