Bridge Scour and Stream Instability Countermeasures

Stream instability is characterized by lateral or vertical instability. Such instability has led to the failure of bridges and loss of life. Lateral instability is caused by lateral migration of the stream or river, while vertical instability can be caused by a combination of contraction scour, long term aggradation or degradation, and local scour. Countermeasures for stream instability and scour are discussed for either existing or new bridges and are recommended for use by the Federal Highways Administration (FHWA).