TXT-tool 2.386-1.1 Intensity-Duration-Frequency Curves for Rainfall-Induced Shallow Landslides and Debris Flows Using Copula Functions

Geological hazards such as debris flows or deep-seated landslides can cause major economic damage and endanger human lives. In order to warn people living in a hazardous area during extreme meteorological events that may trigger debris flows or landslides, in many parts of the world different early warning systems (EWS) have been developed and installed. Empirical rainfall thresholds can be applied as a part of advanced early warning systems. This study combines two concepts: (i) empirical rainfall thresholds and (ii) intensity-duration-frequency (IDF) curves, that both include information about rainfall duration and rainfall intensity. The IDF curves were constructed using a copula function. Post-event analysis of several extreme events in Slovenia, Europe, in the last 25 years was carried out. The triggering conditions responsible for the initiation of the extreme events were investigated, and several empirical rainfall thresholds were tested. It was found that different meteorological conditions were responsible for triggering deep-seated and shallow landslides. A comparison between empirical rainfall thresholds and IDF curves indicated that some thresholds correspond to a return period significantly smaller than two years. If the IDF curves are incorporated into the early warning systems, this will mean that warnings can be issued with a corresponding probability.