Pier with exposed footing or pile cap

HEC-18 uses superposition method to determine the total scour for this case. The total scour is the sum of the scour components for the pier stem in the flow and the component for the footing or pile cap in the flow.

ys= (ys)pier + (ys)pc
Where:
ys is the total scour depth
(ys)pier is the scour component for the pier stem in the flow
(ys)pc is the scour component for the footing or pile cap in the flow

Please read HEC-18 for details on how to calculate (ys)pier and (ys)pc.