Methods have been presented for computing the probability of bridge failure due to pier scour either using a maximum scour depth model or a time-dependent model. The probability of failure provides the basis for a tool which can be used in decision-making for both design of pier foundations or assessment of existing foundations. In the design of a bridge pier, the engineer can use this method to evaluate various design alternatives as a function of parameters such as the size, shape, and depth of the pier. A particular level of risk over the life of the structure that is socially acceptable could be set by policy. If the computed probability of failure due to scour at an existing bridge is currently high or is approaching an unacceptably high level, engineers would be alerted to a need for inspection and possible control of the scour hole around the piers. Without an estimate of the probability of failure, these decisions would be based only on the engineer's judgment. The computed failure probabilities do not eliminate the need for judgment, but provide valuable supplemental information for decision-making.