Geophysical Monitoring of Landslides–A Step Closer Towards Predictive Understanding?

Landslide early warning is still mostly reliant on precipitation thresholds, which can fail to address the subsurface conditions causing slope instabilities. Here we introduce a novel approach combining the latest developments in geophysical and environmental monitoring, with hydrological and geomechanical modelling to provide robust estimates of current and future Factors-of-Safety of slopes, which we propose may be a robust measure for developing early warning thresholds. We aim to develop a methodology that can predict slope instabilities by estimating the causing subsurface conditions in near-real time, thereby allowing for timely early warning to vulnerable communities and implementation of mitigation measures. It is shown here applied to a hillslope with a history of slope failure, using simplified hydrological and geomechanical models. During the monitoring period, precipitation events are shown to give rise to the local water table, thereby reducing the Factor-of-Safety of the slope. It underlines the value of predicting the effect of future storm (or precipitation) events, that imply an additional reduction and hence an increased risk for slope failure. Although applied to a local hillslope, the same approach can be upscaled to regional scales using emerging and established remote sensing and wireless sensor networks.