Average Bank Slope (in the vicinity of the bridge) - Right Overbank
The average bank slope (Z) of the right side of the channel is the horizontal projection of the slope when vertical is 1. The slope is used to adjust the ground line between the channel and the flood plain. The adjustment modifies the idealized ABSCOUR rectangular sections in order to model a more reasonable geometry for the bank condition. This adjustment provides for a better prediction of the abutment scour depth for abutments with short setbacks.
The bank slope also determines the relative effect of the channel scour on scour at the abutment for abutments with short setbacks. Steeper slopes such as 1:1 will reduce the effect of channel scour whereas flatter slopes such as 4:1 will increase the effect of channel scour. The bank slope can be used as a variable in sensitivity analyses of factors affecting abutment scour. See Contraction Scour, Adjustment for Short Setback Abutment (Case A).
Click here to see a sketch of the average bank slope