Determining Paths of Gravity-Driven Slope Processes: The ‘Vector Tree Model’

In the context of studies about the sediment supply into mountain torrents a Geographical Information System was used as a tool for the simulation of rapidly moving gravity-driven slope processes. It was found that procedures which use regular polygon-cascading as a ‘trajectory model’, sometimes do not calculate realistic paths for slope processes. The reason for this was found in the predecessor — successor relation these procedures establish between two adjacent polygons (triangles of a TIN or grid-cells). These relations turned out to be not transitive, when they do not take into account, that material transported into the considered polygon from a higher polygon is not always homogeniously distributed over the whole area of the considered polygon. Consequently, a new ‘trajectory model’, the ‘vector tree’ model, was developed and tested. In this model the paths are formed by’ sequences of vectors’.’ sequences of vectors’ are established by linking together vectors drawn parallel to the flow direction of the slope. This model has produced realistic results for the areas evaluated.