DAN3D is capable of modeling the major properties of a debris ow. The inhomogeneous debris gets simplied with an equivalent uid concept whose stress state is described by the Rankine theory. This equivalent uid can ow over a complex 3D terrain the interaction of which is described by a basal resistance rheology. This basal shear resistance mainly controls the velocity and behavior of the runout. Material entrainment can be included into the model. Its kinematic eect on the runout is described by the conservation of momentum and a continuous update of the debris volume.
The debris unit weightγ, the friction coecientf, the turbulence coecientξ, the internal friction angle φi, the erosion rate Es and the source volume V were varied in order to nd out the inuence on the results using a simplied terrain. The results which were compared where the maximum deposit height, runout length, deposit area, deposit volume, maximum velocity and mean velocity. Comparing the range of the results for each parameter set provided information to create correlations between the input parameters and the results.
It showed that the unit weight had a negligible or rather uncorrelated inuence on the re-sults and can therefore not be used to control the runout behavior. The friction coecient has the biggest inuence on the results. Increasing the friction coecient by 100 % results in a 250 % heigher deposit, a 300 % shorter runout and a 300 % smaller deposit area.
The turbulence coecient has a smaller impact on the results. Increasing the turbulence coecient by 100 % results in a 35 % lower deposit height, a 40 % longer runout an a 40 % bigger deposit area. The internal friction angle has an even smaller inuence. It
mainly controls the deposit height, runout length and deposit area and has only small inuence on the deposit volume and velocities. The erosion rate variation showed a linear correlation on the runout length and deposit volume . Increasing the erosion rate by 100
% results in a 100% longer runout and a 170% bigger deposit volume. It has a small in-uence on the deposit height and runout length and has an even smaller inin-uence on the velocities. The last sensibility analysis was performed using varying source volumes. This showed a linear correlation between the deposit volume and smaller positive correlation on the deposit height, the runout lenght, the deposit area and the velocities. Increasing the source volume results in a faster runout which has a higher deposit, longer runout, bigger deposit area and bigger deposit volume.
In order to perform a runout simulation, a lot of information needs to be available. De-pending whether the model performs a back-analysis or a prediction, dierent variables need to be evaluated. The major dierence between a back-analysis and a prediction is that for a prediction the model parameters and debris source are unknown. Performing a back-analysis may evaluate the model parameters for the prediction of a future event.
Using parameter sets of similar events could deliver the model parameters if there are no recorded events to be back-analyzed. Predicting the source volume is a more complex problem which can be solved using empirical or analytical methods. The correct assump-tion of the debris source is critical for a predicassump-tion and has the same importance as setting the proper model parameters.
The data of the "Seefeldbach" debris ow event could be transformed into the DAN3D grid les. Most information needed to be extracted from the on site photographs due to the lack of discrete source and deposit information, because the pre-event DEM was not accurate enough.
Both the Voellmy and friction rheologies were used to back-analyze this event. Best-t results were generated using the Voellmy rheology with a friction coecient off = 0.1 and turbulence coecient ξ = 500 m/s2. Using the frictional rheology with the bulk friction angle φb = 15◦ produced the best-t result for this rheology. Comparing both results shows that the Voellmy rheology is more capable to simulate this runout.
Errors in the debris deposits result from the usage of the post-event DEM. Neglecting this minor divergence, DAN3D is capable of simulating this debris ow event. It should
be pointed out, that the obtained results could be taken as a prediction for an event with the same source volume. According to the results of the simulations, an event similar to the 2002 event will most probably go over and damage the houses.
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