ABSTRACT
Most slope movements in the Area North of Lisbon exhibit a clear climatic signal, confirmed by the number of movements activated in the wettest years as well as the nearly absolute inactivity in other years. A particular attention is put on the rainfall triggering of landslides verified in 1996 and 2001. The new rainfall data is incorporated in the previous rainfall analysis in order to improve the critical thresholds of precipitation (amount/duration) responsible for landslides events in the study area.
A general threshold was found plotting the cumulative rain and the duration of precipitation. Its validity is confirmed by the correct fitting of 89% of the rainfall events. A second threshold was defined crossing daily rainfall and 30-days calibrated antecedent rainfall. This trend line highlights both 80 mm of calibrated antecedent rainfall and 24 mm of daily rainfall as, simultaneous critical values for landslide triggering in the study area.
