Shallow landslides are a significant hillslope erosion mechanism and can transform into destructive debris-flows. Limited understanding of the controls on debris-flow initiation, development and deposition results in persistent risk and high impacts where linear infrastructure is affected. Here, we analyse steep slopes above a key road, the A83 Rest and be Thankful, Scotland, where near-real-time rain gauge data, time-lapse camera deformation tracking and seismics allow us to define thresholds for increased debris-flow risk, examine long-term slope creep and, detect debris-flow occurrence. We show the patterns and development of channelized and hillslope debris-flows that act as a key geomorphic agent, accounting for 58% of landslide source volume over 13-years. On-slope rainfall data allow us to quantify the effect of antecedent rainfall and storm intensity-duration on landslide triggering and develop new local thresholds over which landslides are likely to occur. To better equip asset managers, we use time-lapse imagery vector tracking to detect slope instabilities, and deformation rates to calculate inverse-velocity values to indicate if failure is imminent. Low-cost seismometers are used to detect when a debris-flow has occurred and locate the source area. The suite of sensors has provided vital information both prior to failure, and during debris-flows to support operational decision-making for authorities dealing with complex slope hazards.