Oregon’s Hidden Threat: Thousands of Landslides a Year, Faster and Harder to Predict Than Quakes

Thousands of landslides strike Oregon each year

In a single instant a landslide can destroy a home or sweep away an entire neighborhood. Landslides are not always slow, gradual events: debris flows — mixtures of water, soil and large debris that can travel at speeds up to 50 mph — occur regularly in Oregon and are among the most dangerous types of slope failure.

Why landslides are increasing

Geologists estimate thousands of landslides occur across Oregon annually, and evidence suggests the number is rising. Two major drivers are climate change and expanding development into steep terrain. Climate change intensifies atmospheric rivers — long, moisture-rich air currents from the Pacific — bringing heavier rainfall to the West Coast. Wildfires that strip vegetation and root structure from slopes also make hillside soils far more vulnerable to failure when rains return.

“Over the last couple decades...we've just seen a really dramatic uptick in global impact from landslides,” said Josh Roering, professor of earth sciences at the University of Oregon.

New research and coordination: CLaSH

The National Science Foundation awarded $15 million to create the Center for Land Surface Hazards (CLaSH), based at the University of Michigan, to coordinate research on landslides and related surface hazards nationwide. CLaSH will partner with academic, government and community organizations to study landslide processes in varied settings — from the Pacific Northwest to Appalachia, Southern California, Alaska and Puerto Rico — and work on improved monitoring, modeling and practical guidance for stakeholders.

Mapping the risk: DOGAMI and SLIDO

The Oregon Department of Geology and Mineral Industries (DOGAMI) maintains the Statewide Landslide Information Database for Oregon (SLIDO), built from high-resolution LiDAR mapping. SLIDO shows landslides are widespread: investigators continually discover previously unmapped slides, even in parts of eastern Oregon. In one recent county study DOGAMI identified about 1,500 slides in Wasco County alone.

Where landslides commonly occur in Oregon

Any steep terrain can fail, but hotspots include the Columbia River Gorge, the Upper McKenzie River Valley and the Oregon coast ranges. Historic and recent examples include a deadly November 1996 debris flow in Douglas County that killed four people, a catastrophic year of storms in 1996 that produced an estimated 15,000–20,000 slides statewide, and a 2021 fatality in the Columbia River Gorge when a driver was swept away.

Types and impacts

Landslides range from fast-moving debris flows to deep-seated slides that can originate hundreds of feet below the surface and move only inches per year but still threaten homes and infrastructure over time. DOGAMI’s study of Eugene and Springfield identified more than 700 landslides covering roughly 6% of the study area; over 4,500 residents live on existing deep-seated slides and about $476 million in buildings sit on those slopes.

Personal stories: insurance and recovery

Homeowner Sihu Klest of South Eugene experienced a March 10, 2024 retaining-wall failure that triggered a landslide and forced evacuations of nine homes. Klest discovered her policy excluded “earth movement,” leaving her family to cover evacuation and repair expenses until they switched to a broader policy. Insurance coverage for landslides is limited: most standard homeowner policies exclude earth movement, while debris flows may be covered under flood policies in some cases, according to the Oregon Health Authority.

Preparedness and safety advice

DOGAMI urges Oregonians to monitor the weather and heed warnings from the National Weather Service. The most dangerous slides are debris flows triggered by intense rainfall and flooding. Key advice:

• Stay alert: follow radio, TV, weather radio or online updates and evacuate immediately if ordered.
• Listen for unusual sounds: cracking trees or rumbling rock can indicate imminent movement.
• Watch streams: sudden muddy water or abrupt changes in flow can mean upstream failure.
• Exercise caution on roads: embankments may fail and debris can block or undermine pavement.
• Check SLIDO or contact DOGAMI to learn local susceptibility before buying property or building.

Prediction remains difficult

Scientists still struggle to answer the central questions: When will a landslide occur, how large will it be, and how far will it travel? Unlike earthquakes, which follow fault lines with measurable histories, landslides vary widely in scale, triggers and underground failure points. CLaSH will focus on improved prediction through sensors, modeling and field studies; collaboration with the Cascadia Region Earthquake Science Center (CRESCENT) will also explore links between seismic activity and slope failures.

Research serving communities

CLaSH outlines four priorities: respond to emerging surface hazards; build predictive tools and simulations; integrate surface-hazard science into education; and work directly with transportation agencies, planners and emergency managers so research leads to practical mitigation, planning and response. Researchers hope this investment is a starting point for long-term collaboration and funding.

Resources: Visit DOGAMI’s SLIDO mapping tool to check local landslide susceptibility, and review flood and evacuation guidance from the National Weather Service and local emergency managers.

Reporting by Miranda Cyr for The Register-Guard.