alabama said:The picture of the ford bridge from the top shows heavy scour on the down stream side also known as an undercut. Unless the undercutting is stopped it won't be long until water starts to flow under the concrete and then it won't be long until that structure is gone. It is a natural process of stream degradation.
If you are lucky you can slow it down by placing grout bags in the scour hole under the structure but head pressure from the up stream side will find its way under. Driving sheet pile will correct the problem but a new structure will be cheaper.
Oops sorry but it is a habit.