Overview ROFMOD

Modelling the velocities, bounce heights and run-out distances of a falling block is a valuable tool for assessing the hazard potential and the dimensioning of protective structures in areas at risk from rockfall. 2D modelling is suitable where, with good knowledge of the local rockfall activity, meaningful analyses regarding protective measures are to be carried out with little effort.

The 2D rockfall modelling software ROFMOD 5.0 consists of a central module for the calculation of fall trajectories, a module for the simulation of protective dams and a user interface which controls data input and output.

The model approach of the central calculation module can be summarized as follows: A maximum of 500 fall lanes are calculated on a terrain profile. The starting points are generated equally distributed within a definable starting zone. The entire profile is divided into a calculation grid with a freely selectable resolution. When a block passes through a cell of the calculation grid, the current movement parameters bounce height, translation energy, rotation energy and speed are recorded. In addition, for each grid cell it is determined how many blocks reach or pass through this cell.

For each calculation grid cell, statistical key figures are calculated for the motion parameters mentioned: The maximum values (100% quantile), the median values (50% quantile) and the calculated values for a freely selectable quantile (between 51% and 99%).

It is very important to note that ROFMOD 5.0 is a deterministic model. This means that the model parameters are fixed by the user for a certain scenario. In contrast, in a probabilistic model the model parameters are varied by the software within a value range.

The significance of the modelled quantiles is therefore very different for the two model approaches: The wide range of results of probabilistic modelling usually has to be limited via quantiles, but not in deterministic modelling. Here an active variation of the modeling parameters with scenarios by the user is of central significance.

The user interface of ROFMOD 5.0 is the interface to the calculation module. Due to the direct graphical representation of the input data and the modeling results, erroneous basic data can be recognized and corrected immediately.

The work with ROFMOD 5.0 is basically divided into three sub-areas: acquisition of the terrain model (2D profile and terrain condition), modelling of the fall paths (rockfall simulation) and presentation of the results (layout and graphics). When working on a project, these three sub-areas are run through iteratively: Only the variation of the model parameters (with the new scenario manager) and possible refinement of the basic data together with the observations in the field lead to a good understanding of the rockfall activity on a real terrain section.

Optionally, a defined protective dam can be simulated with the modelled fall trajectories as input. Detailed statistics of the fall trajectories and their impact on the protective dam provide important information on the location and geometry of the dam.