Experimental study of energy dissipation over stepped gabion spillways with low heights

Stepped gabion spillways have many applications in dam structures, river engineering, and soil conservation works. They are more stable and flexible than their rigid (impervious) counterparts. Moreover, their stilling basins can be constructed at lower costs as energy dissipation in these spillways is high due to both over-flow and through-flow. This study aims to study the over-flow and through-flow in gabion stepped spillways and to evaluate their energy dissipation. For this purpose, eight physical models of gabion stepped spillways with three different porosities (38, 40 and 42%) and two slopes (1:1 & 1:2) (V:H) were made with permeable and impermeable faces of both horizontal and vertical types. Results showed that at higher discharges, energy dissipation was greater in pervious (gabion) spillways than those with impermeable horizontal or vertical faces. At lower discharge rates, however, energy dissipation was greater in impervious stepped spillways. On the other hand, steps with impervious vertical faces had more energy dissipated than those with impervious horizontal faces. Increasing gabion porosity increased energy dissipation, but this effect was minor at higher discharges. Finally, it was found that decreasing slope led to more energy dissipated.