Abstract: 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 in Iran. Model
calibration was performed by collecting different field data. Field data are cataloged on three categories, first group of bridges that
their rivers bed are formed by fine material, second group of bridges
that their rivers bed are formed by sand material, and finally bridges that their rivers bed are formed by gravel or cobble materials.
Verification was performed with some field data in Fars Province. Results show that for wide piers, computed scour depth is more than
measured one. In gravel bed streams, computed scour depth is greater
than measured scour depth, the reason is due to formation of armor layer on bed of channel. Once this layer is eroded, the computed
scour depth is close to the measured one.