Outburst floods triggered by impulse waves: insights from hydraulic experimentation

Outburst floods represent a serious hazard in mountainous regions. A major trigger for these events are impulse waves generated by mass wasting into the water bodies including artificial reservoirs for hydropower generation, lakes impounded by a landslide dam, or moraine dammed proglacial lakes. After a short propagation distance, these impulse waves overtop the dam and erode its top. If the erosion is substantial enough, a dam breach is initiated. The stages leading to an outburst flood were represented by three different hydraulic model setups: impulse wave generation and spatial propagation in a wave basin, wave overtopping in a 2D wave channel, and spatial dam breach in a 1 m wide flume. Selected experiments are presented and the characteristic hydraulic features as well as governing parameters are discussed. The results support an improved hazard assessment and are useful to further develop existing numerical schemes