This book is a compendium of 75 papers and 321 abstracts presented at conferences sponsored by the Water Resources Engineering (Hydraulics) Division of the American Society of Civil Engineers from 1991 through 1998. It contains many new and expanded versions of the original papers, and is designed to assist the practitioner with the concepts in evaluating stream instability and scour at bridges. Some topics include: history of bridge scour research; bridge scour determination; stream stability and geomorphology; construction scour; instrumentation for measuring and monitoring; field measurement; computer and physical modelling of bridge scour; scour at culverts; and economic and risk analysis. One important paper contains 384 field measurements of local scour at piers made by the U.S. Geological Survey.