THE DETERMINATION OF STATISTICAL AND DETERMINISTIC HYDROLOGICAL LANDSLIDE-TRIGGERING THRESHOLDS

Hydrological landslide-triggering thresholds separate combinations of daily and antecedent rainfall or rainfall intensity and duration that triggered landslides from those that failed to trigger landslides. The y are required for the development of landslide early warning systems. When a large data set on rainfall and landslide occurrence is availab le, hydrological triggering thresholds are determined in a statistical way. When the data on landslide occurrence is limited, deterministic models have to be used. for shallow landslides directly triggered by p ercolating rainfall, triggering thresholds can be established by means of one-dimensional hydrological models linked to the finite slope mod el. in the case of relatively deep landslides located in topographic h ollows and triggered by a slow accumulation of water at the soil-bedro ck contact, simple correlations between landslide occurrence and rainf all can no longer be established. Therefore real-time failure probabil ities have to be determined using hydrological catchment models in com bination with the infinite slope model.