Temporal clear-water scour evolution at rock weirs

Rock weirs are commonly used eco-friendly river training structures. However, water flow over rock weirs can cause local scour, resulting in structural failure. To improve the prediction accuracy of scour dimensions at rock weirs, flume tests were conducted to study the clear-water scouring process at rock weirs. Additionally, the effects of flow intensity, submergence, and weir permeability on scour development were analyzed. The results reveal that for clear-water scour, the scour hole develops fast initially before progressively slowing down. At a specific time, the clear-water scour depth and length increase with increasing flow intensity and decrease with increasing flow submergence. The increase in weir permeability increases the scour length but decreases the scour depth. Moreover, as scour develops, the scour hole profile converges gradually, and its area is linearly and positively correlated with the product of the scour depth and length. Based on the experimental data and theoretical analyses, predictors for calculating the temporal clear-water scour depth, length, and volume at rock weirs are proposed for designing purposes.