Abstract
This paper presents short case histories where stream instability has led to the failure or partial failure of a bridge. In this context, stream instability can be characterized by either lateral instability or by vertical instability. In general lateral instability is caused by lateral migration of the stream or river, while verticalinstability can be caused by a combination of contraction scour, long term aggradation or degradation, and local scour. In this paper, the design of three principal common countermeasures will be discussed. These include spurs, check dams, and guide banks. This paper appears in transportation research record no. 1290, Third bridge engineering conference, march 10-13, 1991, denver, colorado, volume 2.