Laboratory debris flow channel

The laboratory at the WSL offers the possibility to investigate debris flows at a small scale. This allows scientists to study, for example, flow behavior for various natural materials, investigate debris flow impact, explore the erosion process, and test instruments before deployment in the field. Small-scale instrumentation such as laser and pore water pressure probes as well as large-scale infrastructure such as an overhead crane and large pumps permit facilitates the work in the laboratory. The channel is also used to illustrate the debris flow process for visitors.

Debris Flow Process and Hazards

Debris flows are mass movements with a flow behavior resembling both landslides and floods. They often occur following intense rainstorms or lake or dam failure, and typically move rapidly down a valley as a series of waves or surges. The flow process depends on the interaction of the solid and fluid phases, as well as the properties of the sediment mixture such as the distribution of grain sizes and the presence and amount of clay and silt in the sediment. Some debris flows appear to have a dry boulder-rich front and move quickly down a channel, destroying everything in their immediate path, other debris flows move more slowly and flow around small objects in the flow path; sometimes evidence of both types is found following a debris flow in the field. In any case, debris flows may cause significant damage and even loss of life.

Project “Debris Flow” as an example of the use of the channel

As part of a research project financed by the ETH Board, WSL scientists examined the erosive behavior of debris flows in the laboratory channel. The focus was on the common boulder-rich variety, and natural sediments from recent debris flows were used in the experiments. Erosion of the channel bed was also investigated by placing debris flow material in the channel bed under conditions similar to what would be expected in the field. About 170 experiments were performed and the processes were investigated by systematically varying the properties of the sediment mixture, such as the water content. Before and after each experiment, the topography of the channel was measured to assess erosion.

A debris moving down the channel	A debris flow deposit

For more information:

The experiments described above were made by D. Weber as part of his doctoral dissertation. The abstract of his dissertation (in German) is available online (Abstract PDF, 208 KB) and a limited number of paper copies are available. Recent experiments on debris flow impact are also described in a doctoral dissertation at ETH by Corinna Wendeler (2008).

Kontakt

• Brian McArdell