What bad thing can happen to a bridge support if 'scour' happens around its base?

Scour is the erosion and removal of streambed material, such as sand, gravel, or soil, from around a bridge support's foundation by the force of flowing water, creating a deepened hole. The bad thing that happens when scour occurs is the critical loss of foundation support. The foundation, which is the substructure component (like piles, caissons, or footings) designed to transfer the bridge's weight and other loads into the ground, becomes und....