Landslide-related weather thresholds

The document is the deliverable of WP3 "Meteorological Dynamics: Knowledge, tools &methodologies contributing to a landslide multi-hazard framework" and describes the actions performed in Task 3.4 "Analyse & develop weather-based thresholds for short-term (1 day to weeks) landslide forecasting". The main goal of the activity is the definition of empirical rainfall thresholds for the possible initiation of landslides in the Darjeeling and Nilgiris test sites. The report describes the empirical cumulated event rainfall - rainfall duration (ED) thresholds for the Darjeeling and Nilgiris test sites. For the purpose, a tool for the objective and reproducible reconstruction of rainfall events and of rainfall conditions responsible for landslides was used. The reconstructed rainfall conditions were then revised by expert investigators to take into account (i) the local rainfall regimes of the two test sites (presence of monsoons), (ii) the coarse (daily) temporal resolution of rainfall measurements and (iii) the possible inaccuracy in the landslide occurrence date. A frequentist statistical method was adopted to define ED thresholds for different non-exceedance probabilities in the two test sites. Additionally, we conducted an analysis of the magnitude of the rainfall conditions responsible for the landslides.