BRI-STARS (BRIdge Stream Tube model for Alluvial River Simulation) program was used to investigate the scour depth around bridge piers in some of the major river systems inIran.
Model calibration was performed by collecting different field data. Field data are cataloged on three categories. The first group of bridges having river beds formed by fine material (i.e., silt and clay), the second group of bridges having river beds formed by sand material, and finally, bridges having river beds formed by gravel or cobble materials. Verification involved application and comparison of the model to different known real-life cases. The results of this comparison determine the validity and quality of the calibration. Verification was performed with some field data in Fars Province. The scour depths of various bridges located in Iran during significant floods were calculated. The bridges are located in three different locations with different bed materials such as: the Ghadir Bridge on the Zayanderood River, the Khan Bridge River and the Chame Sohrabkhani Bridge on Kor.
Results show that for wide piers, computed scour depth is more than the measured depth. In gravel bed streams, the computed scour depth is also greater than measured scour depth, the reason is due to the formation of the armor layer on the bed of the channel. Once this layer is eroded, the computed scour depth is close to the measured one.