Mapping Persistent Soil Moisture Across Ireland’s Rail Network Using Sentinel–1
As Ireland faces increasingly wet winters and more frequent weather events, understanding how the ground beneath critical transport infrastructure responds to these changes has never been more important.
Soil moisture is a key factor influencing how well the land supports and stabilises rail lines, embankments, cuttings, and adjacent terrain. To gain deeper insight into these dynamics, Sentinel–1 Synthetic Aperture Radar (SAR) data were analysed within Google Earth Engine (GEE) to map soil conditions along Ireland’s railway network.
The objective of the study was to identify locations where the ground remains consistently wet, year after year, an indicator of potential maintenance issues. The maps and data outlined below were produced by Mallon colleague Micheal Foley.
Why Soil Moisture Matters for Rail Infrastructure
Soil moisture plays a critical role in determining the strength and stability of railway foundations. When soils remain saturated for prolonged periods, pore water pressures increase, reducing shear strength and leaving embankments or cuttings more vulnerable to deformation or failure.
Persistent high moisture can contribute to:
Track settlement or loss of alignment
Ballast fouling and reduced drainage capacity
Slope instability or erosion along embankments
In Ireland, where rainfall is frequent and clay–rich or peatland soils are common, these risks are particularly relevant. Even subtle shifts in soil moisture can have long–term effects on asset performance,
resilience, and maintenance budgets.
Using Sentinel–1 to Monitor Moisture at Scale
Sentinel–1 radar imagery provides a powerful way to monitor soil moisture across large areas, unaffected by cloud cover or seasonal changes in daylight. Radar backscatter responds to the surface, which changes as soils become wetter or drier.
In this study:
Sentinel–1 backscatter was used to estimate surface soil moisture
Moisture values were scaled between 0 (very dry) and 1 (saturated)
Values above 0.6 were considered indicative of high near–surface moisture, often associated with reduced ground strength or limited drainage
Mapping the Rail Corridor
The Irish rail network was extracted from OpenStreetMap and buffered by 250 metres, creating a rail corridor that captured tracks,
embankments, drainage zones, and surrounding terrain.
For each year, 2023, 2024, and 2025, median soil moisture values were calculated within this corridor. Comparing these yearly datasets made it possible to identify:
Areas where moisture consistently exceeded 0.6
Locations with chronic wetness rather that short–term saturation
Terrain features or drainage patterns contributing to ongoing vulnerability
This multi–year perspective provides a more reliable indicator of long–term ground behaviour than single–event measurements.
Identifying Persistent Moisture Hotspots
Consistently high soil moisture is not necessarily an indication of imminent failure. However, when the ground remains wet for multiple consecutive years, it can indicate long–term susceptibility to:
Drainage inefficiency
Low–lying or poorly draining terrain
Moisture–sensitive soil types
Seasonal or climate–driven saturation cycles
These insights can help rail asset managers move from reactive maintenance to proactive, evidence–based planning.
Benefits for Infrastructure and Asset Management
Integrating satellite–derived soil moisture into existing inspection and maintenance workflows offers several advantages:
Prioritising inspections along moisture–sensitive segments
Support drainage design and upgrade planning
Identify high–risk locations early, before issues escalate
Strengthen climate resilience planning through long–term trend analysis
Reduce reliance on extensive physical instrumentation, thanks to scalable national–level monitoring
The use of Sentinel–1 and GEE makes this approach repeatable, cost–efficient, and suitable for continuous nationwide monitoring.
Future Opportunities
This research highlights the growing value of Earth Observation for proactive rail infrastructure management. Future developments could integrate:
Rainfall datasets
Soil classification and permeability data
Ground motion measurements from InSAR
Localised field or sensor–based verification
Bringing these datasets together can help build a comprehensive understanding of how Ireland’s rail corridors are responding to changing environmental conditions.
Soil moisture map intensity
Soil moisture map Portlaoise
Towards Predictive Maintenance
By combining multi–year soil moisture trends with other environmental and structural datasets, transport authorities and engineers can begin shifting toward a predictive maintenance framework – where emerging risks are identified early, interventions are better targeted, and assets become more resilient to climate–driven change.
Further Information
For further information about the methods used to produce the study and maps above, or to discuss your Earth Observation requirements, contact us below.
