Practical Approach to Estimating Realistic Depths of Abutment Scour

Observations of bridge abutment scour lead to a practical new approach for estimating realistic scour IIHR-Hydroscience and Engineering depths at bridge abutments. Prior design approaches usually led to unrealistically deep estimates of abutment scour depth. The observations presented stem from flume experiments conducted with abutments with approach embankments subject to a range of erodibility conditions: fixed embankment on fixed floodplain; riprap-protected erodible embankment on readily erodible floodplain, and unprotected readily erodible embankment on readily erodible floodplain. The approach discards the old notion of linearly combining bridge-waterway constriction scour and local scour at the abutment structure, a notion that laboratory experiments do not support. Instead, the approach entails estimating an abutment-induced local amplification of constriction scour at the bridge opening, and separately estimating a maximum local scour depth at the abutment when exposed by embankment failure.