Contracted Section Overbank Flow Depth Adjustment
For a short abutment setback, the flow depth at overbank area at downstream end of the bridge shall be adjusted to account for a
gradual change from channel flow depth to overbank flow depth. A constant bank slope is used to calculate this transition.
For the purpose of the adjustment, the setback limit is the horizontal bank slope length. When the abutment setback exceeds this limit,
no adjustment is required. When the abutment setback is between 0 and this limit, the program adjusts the overbank flow depth as follows,
(y0)adj=yc-setback/Z
Where:
Z = bank slope horizontal projection when vertical projection is 1.
yc= before scour downstream section average channel flow depth
setback= the distance from the edge of channel to the face of the abutment for vertical and wingwall type or toe of the slope for the spillthrough type
(y0)adj= adjusted downstream section overbank average flow depth.