This document identifies and provides design guidelines for bridge scour and stream instability countermeasures that havebeen implemented by various State departments of transportation (DOTs) in the United States. Countermeasure experience,selection, and design guidance are consolidated from other FHWA publications in this document to support a comprehensiveanalysis of scour and stream instability problems and provide a range of solutions to those problems. Selected innovativecountermeasure concepts and guidance derived from practice outside the United States are introduced. Managementstrategies and guidance for developing a Plan of Action for scour critical bridges are outlined, and guidance is provided forscour monitoring using portable and fixed instrumentation.