Flume Experiments Evaluating the Efficacy of a Large Wood Trap Featuring Horizontal Rods

Abstract

Large wood (LW) disasters, which often accompany sediment-related disasters, occur worldwide. To prevent and mitigate such disasters, we developed a unique LW trap featuring horizontal rods aligned with the flow. When LW enters the trap, it is scooped up by the rods and thus separated from water and sediment. We explored trapping efficacy using a flume of slope 0.087. Water circulated at a constant rate of 1.8 L/s, LW was added to the flow, and the trapping rates were measured. We focused on the relative wood length (Lw) with respect to the horizontal rod spacing (Sr), the number of LW units supplied, and the supply rate. A longer relative length (Lw/Sr) of LW was associated with a higher trapping rate. The trapping rate was also high when the LW number or supply rate was high. The critical Lw/Sr value was 1.5; below this value, LW was not trapped. This study yields the basic information needed to design traps featuring horizontal rods to mitigate LW-related disasters.

Modeling Large Wood Transport in Semi-Congested Regime with Multiple Entry Points

“…Their efficiency in retaining wood during floods was assessed with flume experiments conducted both without [14][15][16] and with sediment transport [17]. As the backwater rise is reduced for smaller rack angles with respect to the horizontal, an attempt to install horizontal rods was also performed [18], showing that the trapping efficiency is smaller than that of vertical racks and that it depends on the ratio between rod spacing and wood length. To reduce the backwater rise, a recent solution, tested in flume experiments [11], employs two vertical racks on the riversides inclined upstream.…”

Impact of Large Wood on River Ecosystems

“…Furukawa et al [22] used flume experiments to develop a novel LW trap consisting of horizontal rods aligned with the flow. The goal was to separate LW from water and sediment, as LW deposits on the horizontal rods.…”