Author(s): Wenzhe Li; Zhaoyin Wang; Zhiwei Li
Keywords: Step-pool system; Energy dissipation ratio; Experiment; Flood discharge
Abstract: Step-pool system widely occurs in high gradient mountain rivers. Step-pool system dissipates flow energy efficiently, thus creates high resistance and stabilizes the stream bed. This paper studies the energy dissipation ratio of step-pool system in different flood discharges. Two types of step pools structures were modeled in the experiment and the energy dissipation ratios at different flood discharges were compared. The experiments were done in the JiangJia Ravine in Dongchuan, Yunnan province. A channel mimicking the natural rivers was dig on the debris flow deposit of the ravine. The different flood discharges were created by a manmade pond in the upper reach of channel. The step-pool structure was made of boulders of 0. 3-0. 5m in diameter. The first type of the step-pool system is a single step and a deep pool, the step of this type is constructed with 7 key boulders. The second type of the step-pool system is composed of several steps and a relatively small pool. The first type is much more in three dimensional than the second type. The results show that the energy dissipation ratio of step-pool structure is as high as over 90% . The role of energy dissipation of the structure becomes smaller as the flood water inundates the whole structure, thence the energy dissipation ratio reduces with the flood discharge. The first type of the step-pool has higher energy dissipation ratio than the second type at various discharges. Better design of a step-pool structure may reach the highest energy dissipation ratio.