The modelling of debris flows was given more attention in Slovenia after the catastrophic event that occured in the village of Log pod Mangartom in November 2000 and that caused large economic damage (more than 15 milion EUR) and claimed seven human lives. With the help of computer programs for mathematical modelling of debris flows, hazard mapping of debris-flow prone areas can be carried our in order to mitigate and reduce the impact of these events.
This Master’s thesis starts with an overview of the numerical debris-flow simulation model named RAMMS (Rapid mass movement) that was developed by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL. RAMMS model is described and presented and the debris flow module is introduced. The work proceeds with a sensitivity analysis of the input parameters and sensitivity is evaluated using NSI (Normalized Sensitivity Index). Because RAMMS uses a Voellmy-fluid friction model that divides the frictional resistance into two parts, special emphasis is given to the sensitivity analysis and to the understing of the role of these two parameters on the RAMMS model results.
In the second part, the thesis focuses on calibration of the RAMMS model for the 2000 debris flow event in the Log pod Mangartom.and the model results are compared to the model results calculated by the program PCFLOW2D.
Debris flows stop due to their rheological properties in large and flat valleys where they form tipical morphological features named fans. Debris fans are generally steeper than the fans formed by torrential processes. Therefore, fan slopes are used as an indicator of possible debris flow occurrence in the debris-flow hazard mapping. Therefore, the third part of the thesis focuses on a sensitivity analysis of one selected Voellmy parameter that has the largest impact on model results. Further, sensitivity analysis is used to evaluate impact of different values of the parameter µ on the fan slopes. The results indicate that fan slopes simulated by the RAMMS have similar values as those that can be found in the natural environment and for which some authors have calibrated historical debris flow events using RAMMS.