Incorporate the effects of scour in the determination of shaft and pile penetration. Design the foundations so that the penetration and resistance remaining after the design scour events satisfies the required nominal axial and lateral resistances. Both reduced geotechnical resistances and increased unsupported length in the columns must be accommodated for in design.

Scour at the foundations is not a force effect. However, scour can change the substructure conditions and topography and alter the consequences of force effects acting on the structure and foundations. AASHTO LRFD Bridge Design Specifications Article 2.6.4.4.2 requires changes in foundation conditions resulting from the design flood be evaluated at the strength and service limit states. Foundation condition changes from the check flood are to be considered and evaluated at the extreme event limit state.

Refer to the for background to aid when determining total scour on any specific design flood and check flood for design purposes.

Design the foundations to resist debris loads occurring during flood events in addition to the loads applied from the structure.