You can use fibre optics to predict landslides

The aftermath of a landslide in Hiroshima, Japan, last August, which left 74 dead. Image: Getty.

Landslides happen everywhere and in different geological locations. This can be because of flooding, which allows sodden soil to move; it can be because of rockfalls, and slower, continuous movements of land due to gravity. Landslides are particularly dangerous when they happen without warning, as recently happened in India and Japan. Tens of thousands were killed in the Vargus disaster in Venezuela in 1999.

Some places are prone to flooding – even, in the case of India, monsoons – but to know where or when a landslide will happen we need good tools. Currently equipment to measure landslides includes rain gauges, such as those used in the Chittagong region of Bangladesh, which record levels of rainfall that can then be compared to previous data of levels that triggered a landslide. But many current systems use point-based sensors: in other words, systems that rely on ground-plugged devices that are able to monitor only from fixed positions.

We’ve been working on a new way of predicting landslides using optical fibres in cables as sensors. The system, called Stimulated Brillouin Scattering, uses the interaction of light with acoustic waves. When installed, it can constantly monitor changes happening to the land; when the soil undergoes collapse or sliding, we can detect the embedded fibre stretching.

These sensing optical fibre cables can be embedded in shallow trenches in the ground, to monitor both large landslides and slow slope movements through the elongation induced in the sensing fibre. If you imagine the land as a body, a distribution of these optical fibre sensors act as the “nerve system”. They have the ability to detect a change of one centimetre over a distance of a kilometre. Being able to measure and track early pre-failure soil movements, it is then possible to detect the signs of an imminent landslide.

Unlike these conventional tools, optical fibres make measurements along the whole sensing cable, which allows for a fully distributed measurement of land deformation. The advantage is the continuous monitoring of large areas with high accuracy. They can also be used in difficult-to-access places, for example underneath bridges, outside the walls of tunnels, near dams and along pipelines and railways in remote rural areas.

In traditional point-based systems you have to be lucky to place a sensor in the critical position where something happens, otherwise you miss the event. But these sensors can be used to cover very large areas with a single fibre cable, and to pinpoint the location of failure signs anywhere within a zone of several square kilometres. 

The optical fibres can also be controlled from a remote point, so fibres can be laid and left with no need for regular inspections; the data is transmitted via wireless or optical fibre networks. They are also cheaper than traditional point sensors, because a single fibre does the trick and no in-situ visits are required.

Optical fibres have been used to measure creep in road boundaries and to monitor bridges and pipelines. So far, only small-scale tests have been used with regard to landslides. But we believe they could change the way we measure and predict these deadly occurrences. The Conversation

 

Luigi Zeni is professor of electronics at The Second University of Naples. He is affiliated with the Italy Research Consortium on Advanced Remote Sensing Systems (www.corista.eu) and Optosensing (www.optosensing.it).

This article was originally published on The Conversation. Read the original article.

 
 
 
 

CityMetric is now City Monitor! Come see us at our new home

City Monitor is now live in beta at citymonitor.ai.

CityMetric is now City Monitor, a name that reflects both a ramping up of our ambitions as well as our membership in a network of like-minded publications from New Statesman Media Group. Our new site is now live in beta, so please visit us there going forward. Here’s what CityMetric readers should know about this exciting transition.  

Regular CityMetric readers may have already noticed a few changes around here since the spring. CityMetric’s beloved founding editor, Jonn Elledge, has moved on to some new adventures, and a new team has formed to take the site into the future. It’s led by yours truly – I’m Sommer Mathis, the editor-in-chief of City Monitor. Hello!

My background includes having served as the founding editor of CityLab, editor-in-chief of Atlas Obscura, and editor-in-chief of DCist, a local news publication in the District of Columbia. I’ve been reporting on and writing about cities in one way or another for the past 15 years. To me, there is no more important story in the world right now than how cities are changing and adapting to an increasingly challenging global landscape. The majority of the world’s population lives in cities, and if we’re ever going to be able to tackle the most pressing issues currently facing our planet – the climate emergency, rising inequality, the Covid-19 pandemic ­­­– cities are going to have to lead the way.

That’s why City Monitor is now a global publication dedicated to the future of cities everywhere – not just in the UK (nor for that matter just in the US, where I live). Our mission is to help our readers, many of whom are in leadership positions around the globe, navigate how cities are changing and discover what’s next in the world of urban policy. We’ll do that through original reporting, expert opinion and most crucially, a data-driven approach that emphasises evidence and rigorous analysis. We want to arm local decision-makers and those they work in concert with – whether that’s elected officials, bureaucratic leaders, policy advocates, neighbourhood activists, academics and researchers, entrepreneurs, or plain-old engaged citizens – with real insights and potential answers to tough problems. Subjects we cover include transportation, infrastructure, housing, urban design, public safety, the environment, the economy, and much more.

The City Monitor team is made up of some of the most experienced urban policy journalists in the world. Our managing editor is Adam Sneed, also a CityLab alum where he served as a senior associate editor. Before that he was a technology reporter at Politico. Allison Arieff is City Monitor’s senior editor. She was previously editorial director of the urban planning and policy think tank SPUR, as well as a contributing columnist for The New York Times. Staff writer Jake Blumgart most recently covered development, housing and politics for WHYY, the local public radio station in Philadelphia. And our data reporter is Alexandra Kanik, whose previous roles include data reporting for Louisville Public Media in Kentucky and PublicSource in Pittsburgh, Pennsylvania.

Our team will continue to grow in the coming weeks, and we’ll also be collaborating closely with our editorial colleagues across New Statesman Media Group. In fact, we’re launching a whole network of new publications, covering topics such as the clean energy transition, foreign direct investment, technology, banks and more. Many of these sectors will frequently overlap with our cities coverage, and a key part of our plan is make the most of the expertise that all of these newsrooms combined will bring to bear on our journalism.

Please visit citymonitor.ai going forward, where you can also sign up for our free email newsletter.


As for CityMetric, some of its archives have already been moved over to the new website, and the rest will follow not long after. If you’re looking for a favourite piece from CityMetric’s past, for a time you’ll still be able to find it here, but before long the whole archive will move over to City Monitor.

On behalf of the City Monitor team, I’m thrilled to invite you to come along for the ride at our new digs. You can follow City Monitor on LinkedIn and on Twitter. If you’re interested in learning more about the potential for a commercial partnership with City Monitor, please get in touch with our director of partnerships, Joe Maughan.

I want to thank and congratulate Jonn Elledge on a brilliant run. Everything we do from here on out will be building on the legacy of his work, and the community that he built here at CityMetric. Cheers, Jonn!

To our readers, on behalf of the City Monitor team, thank you from all of us for being such loyal CityMetric fans. We couldn’t have done any of this without you.

Sommer Mathis is editor-in-chief of City Monitor.