Critical Flow Velocity Under Bridge - Right Overbank

This cell is activated if the user desires to override the value of the critical velocity computed by the program. It will be advantageous to use the override for certain conditions, such as cohesive soils, where the critical velocity is based on factors other than particle size.

The override function should be used with caution and with a full understanding of how the ABSCOUR Program works. Based on the user's input for the Approach Section, the program determines whether the scour condition under the bridge will be clear water scour or live bed scour. If clear water scour, the scour depth is determined on the basis that the average velocity of flow is equal to the critical velocity of the D50 particle size in the bottom of the scour hole. The critical velocity is that velocity, which if exceeded, will move the D50 particle. Please note if the particle size is smaller than the limit for fine sand (0.0007 ft.), then evaluate the cohesive properties of the soil when estimating its critical velocity.

For critical velocities in cohesive soils see this link