Process-Based Design Method for Pier Local Scour Depth under Clear-Water Condition

Accurate estimation of local scour depth has long been considered to be an important step for the design of bridge piers. Methods currently serving in different countries are generally based on equilibrium equations, which have been found to either overestimate or underestimate the local scour depth. In this study, we proposed a new design method for clear-water local scour depth based on temporal evolution characteristics. We collected data from 67 experiments from the referenced literature and conducted four in-house experiments. Using factor analysis and trial calculation, we derived a new temporal equation for local scour depth evolution. Comparison showed that the maximum predicting error of the total 71 experiments was reduced from 162% to 534% using four existing temporal equations to 34% using the new equation. The corresponding design method was illustrated by an idealized scenario. In addition to its understandability and usability, the new method had better flexibility and fault tolerance, because it did not involve the concept of equilibrium scour depth, which lacked an objective and universal criterion.