Abutment Scour Computation: Step 4. Hydraulic Data for the Bridge Section

Using the output data from the water surface profile model, enter the depth of flow, yo in the channel and on the right and left flood plains (1) immediately upstream of the bridge near its upstream face and (2) at a point immediately downstream near the downstream face. The upstream depth will be used to evaluate pressure scour, and the downstream depth will be used as the basis for evaluating contraction scour in the channel and at the abutments. The ABSCOUR program uses an adjusted yo value based on a linear interpolation between the channel depth and the flood plain depth to minimize the abrupt change in depth at the channel bank.

The flow width under the bridge is also required as input data. The flow width shall be measured normal to the flow for skewed bridges. This width times the yo at the downstream bridge section should equals the flow area under the bridge.