Experimental study of bed morphology evolution under two-dimensional dam-break flow

The present study discusses the evolution of bed morphology under 2D dam-break flow by conducting a set of laboratory experiments. The experiments were conducted in a 1.6 m × 28 m × 1.0 m glass flume with non-uniform fly ash as the bed material. Two scenarios were designed: no inflow (scenario 1) and nearly constant water level (scenario 2) in the upstream reservoir. During the experiment, the water levels were measured by pressure sensors which were buried under the sediment layer, and the bed morphology was measured by an ultrasonic ranging system. The results showed that: (1) in scenario 1, the range and depth of the scour pit continued to increase, but the location of the deepest scour point did not change significantly; (2) in scenario 2, the depth and range of scour increased after the dam break, but the growth rate slowed down obviously after t = 15 min. The data can be employed to understand the bed morphology evolution under a dam-break flow, validate numerical approaches, and test geomorphic flood models.