Debris Flow Initiation by Flash Floods in Flume Experiments

Debris flows are destructive events which can quickly alter a landscape and pose a threat to people and property. Debris flows can be initiated by en masse failure of river-bed sediment during a sudden increase in water flow, such as a flash flood; however, the necessary conditions to trigger a debris flow by this mechanism are unclear. To investigate debris flow initiation by flash floods, we conducted a series of experiments in the large tilting flume at the California Institute of Technology. A gate was designed to release a known volume of water as a surge that flowed over a saturated gravel bed. We explored debris flow initiation over a wide range of conditions including different gate heights, bed saturation, and bed slopes. Preliminary results include measurements of surge shape, particle motion, pore water pressure, and ground shaking, and will be used to inform models for flash flood induced debris flows.