We present a long-term spatio-temporal analysis of rock slope evolution
using a Terrestrial LiDAR aiming to improve our understanding of
the link between pre-failure deformation and the spatial prediction
of rockfalls. We monitored the pilot study area located at the Puigcercós
cliff (Catalonia, Spain) over a period of 1,705 days and detected
the deformation of nine different cliff regions together with a high
rockfall activity. An exact match was observed between the progressively
deformed areas and the regions recently affected by three of the
highest magnitude rockfall events, demonstrating a causal relationship
between pre-failure deformation and rockfall occurrence. These findings
allowed us to make a forward spatial prediction of future failures,
hypothesizing a high probability of failure in the six remaining
regions. We observed an exponential acceleration of the deformation
close to failure, in accordance with tertiary creep theory. However,
the temporal analysis of the deformed areas showed a complex and
variable behavior, so no exact prediction of the date of failure
can yet be made. Our findings have broadened our understanding of
the pre-failure behavior of rockfalls and have clear implications
for the future implementation of early warning systems.