Effects of vegetation on aeration and flow resistance of pooled stepped chutes

Pooled stepped chutes enhance energy dissipation and reduce sediment transport in mountain river regulation and debris flow mitigation. They also promote dry-season vegetation growth within channels, potentially influencing wet-season flood hydraulics. This study experimentally investigated air–water flow properties in a 7-m-long, 18.4° sloping flume fitted with a uniform stepped invert. Three configurations – flat steps, pooled steps, and vegetated pooled steps – were compared from the upstream clear-water zone to the downstream fully aerated region. The experimental results show that, compared to flat and pooled stepped chutes, both the mean air concentration and air–water velocity exhibited a reduction in the presence of vegetation on pooled steps. This difference correlated with lower residual energy downstream, indicating that vegetation introduces additional, though typically minor, flow resistance.