How Satellite Technology is Helping Engineers Tackle Invisible Landslide Risk on US-191

Beneath the asphalt of US-191 near Utah's Recapture Reservoir, a slow-moving threat has been quietly reshaping the ground. Over a 500-foot section of the highway's west side, slope instability has persisted for years, undermining pavements, stressing culverts, and clogging drainage systems despite repeated mitigation efforts.

Now, thanks to a collaboration between the Utah Department of Transportation (UDOT) and Geofem, engineers have a far clearer understanding of what's driving this movement and how to manage it.

The culprit? Not just surface water and seasonal storms, but the rhythmic rise and fall of the reservoir itself, interacting with the region's underlying geology in ways invisible to the naked eye.

A Persistent Problem in a Critical Corridor (US-191)

The Recapture Reservoir stretch of the US-191 is more than a local road, it's a vital transportation link for communities, commerce, and tourism in Southeastern Utah. But for years, episodic landslide activity has caused costly damage and maintenance headaches. The instability is unpredictable and, until recently, UDOT lacked a continuous, high-resolution way to link these movements to environmental changes.

A Satellite's-Eye View of Slope Movement

Geofem's team deployed Small Baseline Subset (SBAS) InSAR analysis, processing over five years of Sentinel-1 satellite radar data. The result was a millimetre-precise time series of ground displacement from 2019 to 2025.

They paired this with machine learning models trained on global datasets to estimate soil moisture across the site. By correlating the movement patterns with reservoir level records, the engineers uncovered a striking trend:

• When the reservoir dropped from full capacity, downslope movement accelerated to up to 18mm per year.

• When water levels were high, the slope temporarily reversed, moving up to 10mm upslope before resuming its downward creep.

This wasn't just seasonal swelling and shrinking of the soil. The analysis pointed to subsurface mudstone layers, not surface wetting, as the main driver of the instability. This insight changes how the site will be managed going forward.

Why This Matters

This case highlights a critical point: the forces shaping ground stability are not always visible, and not always where we expect them.

Geotechnical failures often involve complex interactions between hydrology and geology. Without continuous monitoring, such processes remain speculative, leaving engineers to rely on best guesses rather than data-based interventions.

Here, satellite monitoring bridged that gap, enabling UDOT to see cause-and-effect relationships in near real-time. That knowledge can:

• Inform targeted maintenance to focus interventions where movement is greatest.

• Guide design decisions; adapting drainage, reinforcement, and grading plans to the site's unique response to water levels.

• Reduce lifecycle costs by prioritising prevention over reactive repairs.

Lessons for the Future

As climate variability alters rainfall patterns and reservoir management strategies, slope hazards like the one on US-191 are likely to become more dynamic. Construction and infrastructure teams working in such environments should consider:

1. Long term monitoring plans: InSAR offers a cost-effective alternative to dense in-situ sensor networks, with coverage over wide areas.

2. Integrating hydrological data: Water level records, precipitation data, and soil moisture maps can reveal hidden correlations.

3. Geology-first thinking: Subsurface materials often dictate long-term slope behaviour more reliably than surface signs.

The ground may be shifting, but with the right tools, engineers can keep the wheels turning.