Understanding Geohazards and How to Monitor Them

In today’s rapidly changing climate landscape, the threats posed by geohazards are becoming increasingly pronounced and complex. But what exactly is a geohazard?

Geohazards are natural events or processes on the Earth's surface. They can harm buildings and human life.

These can appear in different ways, like earthquakes, landslides, and subsidence. Their effects often go beyond the immediate damage they cause. As the planet's climate changes, these hazards are happening more often and with greater strength. This shows the urgent need for new ways to reduce their risks.

"InSAR transforms raw satellite images into a comprehensive view of geological activities that would otherwise go undetected."

The Growing Threat of Geohazards

Geohazards are different from other natural events because they can damage important infrastructure. This often leads to serious problems. Roads, bridges, pipelines, and buildings are at greater risk.

This is especially true as weather patterns change, sea levels rise, and climate changes worsen geological weaknesses. For example, long periods of drought can cause soil to shrink and sink. Heavy rainfall can also raise the risk of landslides in hilly or mountainous areas.

"Climate change is turning geohazards from occasional threats into persistent challenge for our infrastructure."

This dual threat of natural and climate-related geohazards creates many challenges for planning, developing, and maintaining infrastructure. Without proper monitoring and plans to reduce risks, the effects on society can be serious. These effects can include expensive repairs and even loss of life.

Region	Landslide Risk	Subsidence Risk	Earthquake Risk	Volcanic Risk	Coastal Erosion Risk	Key Contributing Factors
Mountainous Areas	⚠️⚠️⚠️⚠️⚠️	⚠️⚠️️	⚠️⚠️⚠️⚠️	⚠️⚠️⚠️	⚠️	Steep slopes rainfall, freeze-thaw cycles, tectonic activity
Urban Centres	⚠️⚠️️	⚠️⚠️⚠️️	⚠️⚠️⚠️️	⚠️	⚠️	Groundwater extraction, underground construction, heavy building loads
Coastal Zones	⚠️⚠️️	⚠️⚠️️	⚠️⚠️️	⚠️⚠️	⚠️⚠️⚠️⚠️⚠️	Sea level rise, storm activity, weak sedimentary geology
River Valleys	⚠️⚠️⚠️⚠️	⚠️⚠️️	⚠️⚠️️	⚠️	⚠️⚠️⚠️	Erosion, flooding, saturated soils, unconsolidated materials
Arid / Semi-Arid	⚠️⚠️️	⚠️⚠️⚠️⚠️️	⚠️⚠️	⚠️⚠️	⚠️	Groundwater depletion, soil shrinkage, flash flooding
Mining Regions	⚠️⚠️⚠️⚠️	⚠️⚠️⚠️⚠️⚠️	⚠️	⚠️	⚠️	Underground voids, altered hydrology, blast vibrations
Volcanic Regions	⚠️⚠️⚠️⚠️️	⚠️⚠️️	⚠️⚠️⚠️⚠️	⚠️⚠️⚠️⚠️⚠️	⚠️⚠️	Unstable materials, thermal activity, tectonic setting
Permafrost Areas	⚠️⚠️⚠️⚠️	⚠️⚠️⚠️⚠️⚠️	⚠️	⚠️	⚠️⚠️	Climate warming, thawing ground, altered surface hydrology

Table 1: Geohazard Risk Levels by Region and Type

Understanding Geohazards Through InSAR Technology

To address the challenges posed by geohazards, advanced monitoring tools are essential. One such ground-breaking technology is Interferometric Synthetic Aperture Radar (InSAR). This remote sensing technique uses radar-equipped satellites to measure ground movements with millimetre-level precision. By transforming raw satellite images into meaningful data, InSAR provides a comprehensive and dynamic view of geological activities that would otherwise go undetected.

"The dual threat of natural and climate-induced geohazards creates an intricate web of challenges for infrastructure planning."

How InSAR Works

InSAR technology works by looking at small changes in radar signals. Researchers measure these signals when satellites pass over the same area.

Researchers process these phase changes to find even small ground deformations. This helps scientists and engineers track subsidence, uplift, and lateral movement over time. InSAR provides ongoing data that lasts for weeks, months, or even years. This is different from traditional methods, which only give a one-time snapshot.

"With millimetre-level precision, InSAR can detect subtle shifts early, flagging potential risks long before they escalate into disasters."

This temporal perspective is invaluable for understanding the gradual processes that precede major geohazard events. For example, a creeping landslide moves slowly but steadily. This movement may not be easy to see during visual checks or occasional ground surveys.

InSAR can spot these millimetric ground displacements early. It warns us about potential risks before they turn into catastrophic disasters.

Types of Geohazards Monitored by InSAR

InSAR’s versatility makes it an indispensable tool for monitoring a wide range of geohazards, including:

1. Landslides are common geohazards. They often happen because of heavy rain, earthquakes, or human actions like cutting down trees. InSAR helps identify areas of ground movement, allowing authorities to implement preventive measures like slope stabilisation or early evacuation.

2. Ground subsidence is when the Earth's surface slowly sinks. This can happen because of natural causes, like losing groundwater. Human activities, such as mining and oil extraction, can also cause it. InSAR detects even minute levels of subsidence, providing critical data for urban planners and engineers.

3. Earthquakes: InSAR can measure ground changes after they happen. This helps us check the stability of affected areas and guides rebuilding efforts.

Proactive Risk Management with InSAR

One of the most significant advantages of InSAR is its ability to empower proactive risk management. InSAR provides quick insights into ground movements. This helps stakeholders spot potential hazards before they turn into emergencies. This proactive approach saves lives and lowers the costs of reactive responses and expensive repairs.

Early Warning Systems

InSAR’s high precision and wide-area coverage make it ideal for developing early warning systems. In areas at risk of landslides, regular InSAR monitoring can spot slow slope movements. This can trigger alerts for evacuation or other actions. Similarly, in urban areas experiencing subsidence, InSAR data can guide infrastructure maintenance and prevent catastrophic failures.

Cost-Effective Monitoring

Traditional ground-based monitoring methods, such as GPS surveys or borehole measurements, are often labour-intensive and expensive. In contrast, InSAR offers wide coverage at a lower cost. This makes it a better choice for long-term monitoring. This cost efficiency is particularly beneficial for developing countries or regions with limited resources.

InSAR can identify areas of increased ground movement that could precede geohazards, allowing for proactive maintenance.

Informed Decision-Making

The actionable insights provided by InSAR play a crucial role in decision-making processes. Engineers, urban planners, and policymakers can use InSAR data to:

• Prioritise infrastructure investments in high-risk areas.

• Design geohazard-resistant structures.

• Optimise land-use planning to avoid vulnerable zones.

The Future of Geohazard Monitoring

As geohazards become more common and severe, using advanced technologies like InSAR will be more important. However, the future of geohazard monitoring extends beyond individual technologies. It involves a multidisciplinary approach that combines remote sensing, geotechnical engineering, and environmental science to build more resilient infrastructure systems.

"As climate change accelerates extreme weather events, geohazard monitoring becomes critical to building infrastructure resilience."

Integration with Other Technologies

InSAR’s capabilities can be further enhanced by integrating it with other data sources, such as:

• Optical Satellite Imaging: Provides high-resolution visual data to complement radar-based measurements.

• LiDAR (Light Detection and Ranging): Offers detailed 3D mapping of terrain features.

• GNSS (Global Navigation Satellite System): Delivers precise location data to validate and refine InSAR results.

Technology	Coverage Area	Precision	Cost	Frequency	Advantages	Limitations
InSAR	Very Large (100s - 1000s km2)	1-5mm	$$	Weekly / Monthly	Wide coverage, historical data available, works in all weather conditions	Limited in areas with dense vegetation, temporal resolution depends on satellite revisit time
GPS / GNSS	Point-based	3-5mm	$$$	Continuous	Real-time data, high precision, 3D movement detection	Limited to installed points, requires physical access, high maintenance
LIDAR	Medium (1-10 km2)	1-20cm	$$$$	Campaign-based	High-resolution 3D models, works in vegetated areas	Expensive for large areas, requires repeat surveys, weather dependent
Tiltmeters	Point-based	0.1-1mm	$$	Continuous	Very high precision, immediate alerts possible	Very limited coverage, measures only angular changes
Ground-based Radar	Small (1-2 km2)	0.1-1 mm	$$$$	Continuous	Near real-time monitoring, extremely precise	Limited coverage area, requires line of sight, high cost
Extensometers	Point-based	0.01-0.1 mm	$	Continuous	Very high precision- low cost	Extremely limited coverage, measures only one direction
Traditional Surveying	Variable	1-3 cm	$$$	Campaign-based	Flexible, adaptable to site conditions	Labour-intensive, weather dependent, point-based
Optical Satellite	Large (10s - 100s km2)	10-50cm	$	Weekly / Monthly	Low cost, intuitive visual data	Cannot measure small deformations, affected by cloud cover

Table 2: Comparison of Geohazard Monitoring Techniques

Climate Resilience

As climate change speeds up extreme weather events, monitoring geohazards will be key. Building strong infrastructure that can withstand these changes will help us. By incorporating InSAR into climate adaptation strategies, communities can better anticipate and respond to the challenges posed by changing environmental conditions.

"InSAR provides extensive coverage at a fraction of the cost, making it sustainable for long-term monitoring."

Conclusion

Geohazards represent a significant and growing threat to infrastructure systems worldwide. Landslides, subsidence, earthquakes, and volcanic activity can cause a lot of damage and disruption. With advanced tools like InSAR, we can turn this challenge into a chance for better risk management.

InSAR can give continuous, accurate, and affordable data on ground movements. This makes it exceptionally useful for protecting infrastructure from geohazards. By detecting subtle geological changes early, this technology enables stakeholders to act decisively and prevent crises before they occur.

As the need for strong infrastructure increases, using InSAR in geohazard monitoring will be key. This will help us create a safer and more sustainable future.