Plot Scour Cross-Section
The following guidance is provided with regard to drawing the scour cross-section.
- For vertical wall abutments, the preferred method is to plot values of y2 under the bridge, measuring down from the water surface at the downstream side of the bridge.
- Where coefficients have been used to modify the depth of scour, ys , plot the scour depth using the same datum as was used to define yo.
- Where the abutment scour is deeper than the channel scour, use an angle of 30 degrees to define the sides of the scour hole. Use a nominal value of 5 feet to determine the bottom of scour hole.
- Where the abutment scour depths are at a higher elevation than the channel contraction scour, use a smooth curve to define the transition area.
- For an abutment on a spill through slope, draw an arc with center at the toe of the abutment slope and with a radius equals the abutment scour depth.
The arc represents the possible sliding surface of the soil on the slope and also represents the possible scour hole.