What does this research mean for the field?

Unusual long-term rainfall triggers shallow landslides in normally unsaturated sandy and silty slopes by simultaneously reducing suction in the vadose zone and raising the groundwater level. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To evaluate the mechanisms causing shallow landslides in unsaturated sandy and silty slopes during prolonged periods of heavy rainfall.

September 5, 2026Georisk Assessment and Management of Risk for Engineered Systems and GeohazardsOpen Access

Influence of long-term rainfall on the stability of an unsaturated slope in Norway – a case study

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Authors

HHHåkon HeyerdahlNorwegian Geotechnical Institute

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Implication

Case study demonstrates how heavy rainfall reduces suction and raises groundwater in unsaturated sandy-silty slopes, highlighting key hydrological drivers of shallow landslides.

Key Points

To evaluate the mechanisms causing shallow landslides in unsaturated sandy and silty slopes during prolonged periods of heavy rainfall.
Conducted site investigations, soil sampling, and laboratory testing to determine unsaturated soil properties and water retention curves.
Performed transient slope stability and unsaturated seepage analyses under both normal annual rainfall (~800 mm/year) and prolonged extreme rainfall (~240 mm in 30 days).
Slopes remain theoretically stable under normal baseline conditions with precipitation of approximately 800 mm per year.
Rainfall accumulation of roughly 240 mm in 30 days causes progressive stability loss and slope failure via reduced suction in the vadose zone and a rising groundwater table.
Slope stability in intermediate sandy and silty soils is primarily controlled by the interaction between soil cohesion, water permeability, and retention capacity.

Cite This Study

Håkon Heyerdahl (2026) studied this question.

synapsesocial.com/papers/6a9bd3e16b95aff0620eb0f1 https://doi.org/10.1080/17499518.2026.2716834

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Implication

Case study demonstrates how heavy rainfall reduces suction and raises groundwater in unsaturated sandy-silty slopes, highlighting key hydrological drivers of shallow landslides.

Influence of long-term rainfall on the stability of an unsaturated slope in Norway – a case study

Discussion

Member takes

Implication

Key Points

Cite This Study

Influence of long-term rainfall on the stability of an unsaturated slope in Norway – a case study

Discussion

Member takes

Implication

Key Points

Cite This Study

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