Dam-break on Idealised Hillslope: Experimental Measurements of Depths and Surface Velocities

Floods due to the breaching of earthen dams are a potential hazard to downstream areas. The failure of a small dam can affect a limited area and has less devastating consequences compared to the failure of a large one. Nevertheless the presence of many small dams in the same territory is not a negligible risk for the surrounding communities. A lack in emergency plans may result in considerable damage to people life and properties. This requires analysis of potential impacts which imply the ability to predict the potential flooded area and the wave magnitude. The key factor is the estimate of flow depths and flow velocity. [Cordero, S. et al.]. In Italy small (volume less than 1Mm³ and height less than 15m) dams are more than 10000. The majority are earthen dams made for agricultural purpose on hillside and they have no natural outflow. For these reasons, diffusion along the direction perpendicular to the breach axis play a key role in the assessment of the potential flooded area. Many studies in past years focused on the truthful modelling of the wave resulting from a dam collapse. Nevertheless, to the authors’ knowledge, few researchers direct their efforts to the modelling of the dam-break flow using a 3d set-up. A physical model (basically i.e. a 3 x 4 m² plane which can be tilted from 0° to 12° and is set downstream of a 1.125 m³ reservoir) build up in the Hydraulic Laboratory of the Politecnico di Torino is used to imagine the wave propagation by mean of a camera set 3m above the plane. The water depth in any point of the plane can be linked to the dye (red E124) intensity after a calibration procedure. The experiment are conducted both on smooth bed and on an array of 0.05m height rods (0.006m diameter) arranged in 4 different patterns. The results here presented are related to the 0° slope. Surface velocities are given. For this last purpose the flow is seeded by small sphere of 0.005m diameter and 0.9 g/cm³ density.

Cordero S., Cagninei A., Poggi D.,Dam-break on an idealised hill side: Preliminary results of a physical model. E3S Web Conf. 40 05002 (2018). DOI: 10.1051/e3sconf/20184005002