Dam-break-induced three-dimensional viscoplastic flows and debris hazards

This study presents a numerical comprehensive analysis of viscoplastic dam-break flows, with a focus on debris flows influenced by terrain slope and yield-stress rheology. The flow behavior is characterized using key non-dimensional parameters, including the Reynolds and Yield numbers. The numerical framework is validated against experimental observations and benchmark cases to ensure accuracy. The results indicate a critical Yield number that distinguishes between mobile and nearly stationary flows under horizontal conditions. At low Yield numbers, inertial forces dominate, especially at moderate Reynolds numbers, resulting in extended run-out distances and significant deformation of the free surface. As the Yield number increases, the extent of unyielded zones grows, leading to a marked reduction in flow mobility. A polynomial relationship is established to quantify the connection between non-dimensional run-out distance and flow depth across varying Yield and Reynolds numbers. The influence of slope is also investigated, showing a linear increase in run-out distance with slope angle for a given Yield number across a range of Reynolds numbers. A predictive expression is proposed for the critical Yield number as a function of slope and domain geometry, incorporating the height-to-width ratio and slope angle. Finally, the study applies the developed model to historical debris flow events by analyzing corresponding Reynolds and Yield numbers and performing site-specific simulations for the Hobart region using realistic topography. These simulations offer new perspectives on hazard prediction and infrastructure resilience by integrating debris intensity measures and damage indices tailored to viscoplastic flow environments.