New formula for clearwater equilibrium scour depth around a log vane based on literatures

Abstract

River restoration aims to enhance the natural form and processes of a river, often involving techniques to manage the riverbed, stabilize channel alignment, protect stream banks, and rebuild natural habitat methods such as rebuilding meanders, establishing pool-riffle sequences, and managing large wood contribute to stabilizing rivers and restoring habitat. Common measures include the installation of single-wing, double-wing, and triangular deflectors, as well as log vanes constructed along the riverbank to prevent erosion. Despite several studies on the topic, no literature comprehensively covers all the necessary data and equations for thorough comparative analysis. Studying equilibrium scour around log vanes can help fill gaps in understanding the unique mechanisms and characteristics of sediment erosion and deposition, contributing to improved design and management strategies for riverine structures. This study aims to analyze influential parameters affecting the equilibrium scour depth of a log vane through dimensional analysis to develop a new formula for predicting equilibrium scour near the downstream of a log vane. The experimental data utilized in this study were sourced from various literatures where the authors conducted experiments under clear water scour conditions. Upon analyzing these available data, it becomes evident that parameters such as tail water depth, orientation angle of log vanes, aspect ratio of the vane, and downstream water fall significantly influence scour depth. There are two formulas in literatures based on some literature data. However, these two formulas were tested on only a limited number of data. Therefore, a new formula is developed based on all accessible literature data to describe the scour process using nonlinear regression and its dependency on these factors. The statistical performance indicators including coefficient of determination, root mean squared error, sum of squared error, and mean squared error are used for the evaluation of this newly developed formula as well as the two formulas collected from the literatures. Two new formulas have been established which are non-dimensionalized by the length of the vane and height of the vane. These two new formulas outperform the other two literature formulas in terms of all statistical indicators. Furthermore, the scour in the river is influenced by a non-dimensional parameter, y, which is a function of the particle Froude number, height of the log vane and water fall depth. Plotting the data with the new formulas shows a 30% deviation from the perfect agreement line, with no data below -30%, indicating overestimated non-dimensional scour depths and reduced likelihood of structural failure due to scouring.