Debris Flow run out

The term runout length of debris flows refers here to the depositional part or terminal flow path downstream of a defined point; for larger debris flows in the Alps deposition usually occurs on the fan. Although runout prediction of debris flows is essential for hazard assessment, no well established methods are available. The project aims at testing existing and developing new methods. The following methods will be considered for runout estimation: Empirical-statistical approaches refer to methods where the runout distance is typically related to morphometric parameters of the flow path and to the event volume. Analytical methods are those based on a simplified mechanical description of the flow behavior for which analytical solutions are available. Continuum-based mechanical simulation models for debris flows require numerical procedures to solve the differential equations. In the past, similar methods were proposed for the estimation of the runout distance of snow avalanches and landslides/rock falls. Some of these methods were used quite successfully for predicting runout of snow avalanches where sufficient data were available to develop or calibrate the methods. It is expected that similar methods can be developed for runout estimation of debris flows. The emphasis of the project is on larger events occurring in the Alpine region, i.e. debris flows with event magnitudes larger than about 5000 to 10’000 m3. As a basis for the project, existing information on past debris flow events in Austria will be compiled and supplemented by additional information. The newly developed methods for runout prediction of debris flows can be an important and useful tool supporting practical hazard assessment in torrent catchments.