experimental investigation of floating debris passage over stepped spillways with continuous edge obstacles

Stepped spillways are efficient hydraulic structures for energy dissipation. while they are effective, the addition of obstacles to further enhance dissipation introduces a new challenge: the potential for blockages by floating debris. this study experimentally investigates the effect of installing continuous obstacles with different relative heights (h₀/h) on the hydraulic performance of a stepped spillway model in passing floating debris. experiments were conducted in a laboratory flume with a 1:2 slope, four-step spillway model under nappe, transition, and skimming flow regimes (defined by dc/h). continuous obstacles with relative heights of 0.19, 0.38, 0.55, and 0.74 were installed on the step edges. results showed that in the nappe flow regime (dc/h ≤ 0.47), a low relative height (h₀/h = 0.19) caused partial debris trapping, but heights of 0.38 and above ensured complete passage. in transition and skimming regimes (dc/h > 0.85), obstacles at all tested heights were highly effective. the primary mechanism is the local ponding behind the obstacle, which increases buoyancy. this study concludes that, contrary to concerns about increased blockage, installing continuous obstacles on step edges is an effective method to facilitate the safe passage of floating debris on obstructed stepped spillways.