Abstract: Adding piers to open channel chute is a highly efficient approach for enhancing energy dissipation, and holds a significant technological edge especially under specific conditions. This approach remains relatively unexplored within China’s research fields. We conducted a 1∶30 scale hydraulic model test on adding piers to the open channel chute of a rainwater drainage project in Xiaokongtong gully, Qingyang, Gansu. The initial design revealed that the flow regime was unstable, characterized by outward splashing that potentially harms the structural integrity of the loess slopes. In response, we refined the original design by reducing the spacing between the energy dissipation piers. This modification significantly stabilized the flow. Specifically, reducing the pier spacing from H/i to 0.5H/i under peak flow conditions achieved a 72.5% reduction in water surface fluctuation and a 40.10% decrease in average flow rate, leading to a more uniform water depth distribution along the channel and eliminating the splashing. Moreover, the total energy dissipation rate improved markedly, increasing from 87.9% to 94.6%.

Key words: wet collapsible loess area, adding pier to open channel chute, model test, energy dissipation, water surface fluctuations