Effect of tailwater depth and model scale on scour at culvert outlets

The results from an experimental programme investigating the effect of tailwater depth and model scale on scour depths downstream of culverts are shown. Results are presented for cohesionless uniform sands and gravels. A model for predicting equilibrium scour depth and incorporating a correction function to take account of tailwater depth is shown to provide good agreement with previously published work. It is shown that the model scale does have an impact on the reliability with which scour hole data can be presented, in particular those experiments in which Reynolds number falls below 4 × 103.