Abstract: The main objective of this study is to examine the effects of different vegetation densities on the aeration characteristics of artificial pooled stepped chutes. In this experiment, we investigate the behaviors of air water flows in a rectangular stepped pool, with a bottom slope of 18.4° and two vegetation densities, and the development from the upstream clear water region to the downstream fully developed region. Air contents are measured using a conductivity probe. Experimental results show that, compared with flat and pooled stepped, vegetation in a pooled stepped chute has nearly no influence on the location and water depth of the aeration incepting point, and a calculation formula for its water depth is derived. The cross-sectional average air concentration Ce increases gradually from the step start to 2.5 times the aeration point distance, and then reaches a constant. The maximum number of bubbles at the cross section increases gradually from the ladder start to 4.0 times the aeration point distance, and then reaches a constant, showing a different trend from that of air concentration. Vegetation density has little effect on bubble count distribution and evolution.

Key words: pooled step, vegetation, inception point, mean air concentration, bubble count