Protecting hydropower infrastructure: How InSAR detects dam geohazards early

A dam holding back billions of tonnes of water is a symbol of immense power. But what if its greatest threat isn't a dramatic earthquake, but an unnoticed shift in the ground no bigger than the thickness of a coin? For the world’s critical hydropower infrastructure, this early invisible danger is one of the most serious risks. 

These tiny movements—a slow sinking of the ground or a subtle deformation in the concrete—are key indicators of potential geotechnical or structural issues in dams. As tragic events like the 2023 dam breaching flood in Derna, Libya, have shown, such small changes can be the first signs of structural strain that precede a catastrophic break.  

The challenge for engineers has always been spotting these nearly imperceptible clues across a massive structure in time. 

So how can anyone possibly detect millimetre-scale changes before they become a crisis? Advanced satellite technology now provides one of the most effective early warning systems for early avoidance of dam failure, turning invisible threats into a clear, actionable map of risk. 

What is 'dam deformation' and why do a few millimetres matter? 

While a catastrophic earthquake is a clear threat to a dam, a more silent danger comes from slow, imperceptible changes. They may go unnoticed, even during visual inspections, but they can be the early warning signs of a significant defect developing. 

But why does a movement smaller than a coin's thickness matter? Most failures develop gradually – a sudden failure without any warning signs in the weeks and months beforehand is very rare. Failure mechanisms usually need quite large displacements to fully mobilise. They initiate with small, probably unnoticed deformations, as much as years before an eventual, disastrous failure.  

The earlier the initial deformations are noticed, the earlier they can be investigated and proactive measures taken to completely avoid further development of a potential failure mechanism. 

How satellites can help keep dams safe 

The answer to spotting these tiny shifts lies hundreds of miles above us. A specialised satellite captures a precise radar snapshot of a dam and its surrounding landscape. Days later, it orbits over the exact same spot to take a second one, and continues the repeat visits in perpetuity. 

Powerful computers then compare these snapshots, using a method called InSAR (Interferometric Synthetic Aperture Radar) to reveal millimetric shifts across the dam’s surface.  

Incredibly, this satellite radar monitoring can detect changes smaller than a coin’s thickness—all from orbit. Instead of undertaking expensive, regular surveys across the large surface areas of dams, satellites survey large areas in an instant. Problem areas are pinpointed early for targeted action on site. 

The early detection of potential problems allows for proactive maintenance—investigating and fixing a minor issue long before it can grow into a serious threat. 

Ultimately, wide-area dam deformation analysis using satellites provides a new level of security. By pinpointing vulnerabilities in a timely manner, dam operators can get ahead of potential problems, shifting from a reactive approach to a proactive strategy that builds in resilience to dam infrastructure. 

Monitoring of the Shuibuya concrete-face rockfill dam 

A Geofem study employed an advanced Multi-Temporal InSAR (MT-InSAR) technique for monitoring spatiotemporal deformation of one of the tallest concrete-face rockfill dams, the Shuibuya Dam located on the Qingjiang River in  Badong  County, Enshi, Hubei Province in China.  

The estimated deformation signals revealed a consistent vertical settlement trend, with 1D LOS velocities ranging from 0 to -11 mm/year. The most pronounced displacements were observed in the upper section of the dam, while the base and flanks remained relatively stable, which are normal patterns of settlement. Interestingly, these long-term trends occurred in combination with short-term seasonal cycles of deformation.  

These Geofem findings align with historical deformation recorded over the dam and suggest a gradually decreasing rate of settlement. Despite minor geolocation inaccuracies due to external DEM and atmospheric effects, the investigation provides the structural health status of the dam and underscores the value of continued MTInSAR-based surveillance.  

This study underscores the efficacy of satellite-based interferometric techniques in monitoring large-scale infrastructure and advocates for their integration into routine dam surveillance protocols.  

InSAR and ground-based measurement: Why a view from space is a game-changer 

For decades, traditional methods of dam monitoring have involved undertaking regular surveys and placing sensors at some specific points. With this approach alone, there is always a risk that displacement in areas between the monitoring points may go undetected, particularly if they sparsely distributed.  

The key advantage of satellite-based displacement monitoring is that it provides complete surface coverage, filling the gaps between ground-based monitoring points. It also complements traditional methods by providing an independent source of data for comparison and reliability assessment.  

This ability to see beyond the dam itself is crucial. InSAR can spot developing geohazards like an unstable slope above the reservoir that could slide into the water and cause a tsunami with dangerous over-topping.  

As such, it offers a more comprehensive, frequent, and cost-effective overview, providing an unparalleled layer of safety. 

Importantly, satellite monitoring enables retrospective analysis, allowing engineers to examine displacement trends over a ten-year historical period. This long-term view helps assess the impact of external factors like rainfall and seismic activity, improving predictive models and proactive maintenance strategies.

It also provides historical trends to better to understand the trends measured today. Are movements accelerating, perhaps due to climate change and increasingly regular weather extremes? 

Results from large-scale displacement monitoring of Tamasos Dam in Cyprus using InSAR, conducted by Geofem between March 2019 and October 2023. The results closely matched in-situ data, validating measurement accuracy and consistency. 

The future of dam safety: Turning invisible risks into visible confidence 

The biggest threats to our dams are often the ones we cannot see. Where the naked eye sees solid concrete and earth, satellites see a dynamic surface in constant, subtle motion. These satellites spot minuscule movements, transforming invisible dangers into visible, manageable warnings for engineers on the ground. 

This leap in critical infrastructure monitoring changes dam safety from a reactive process into a proactive science. Instead of waiting for a problem, experts can manage risks before they grow. This constant vigilance from above provides more than just data, it offers the quiet confidence that our most powerful structures are being watched over, keeping communities safe. 

Learn how Geofem’s satellite monitoring solutions can safeguard your assets. Get in touch today.