Pilot study for collection of bridge-scour data

Scour around bridges is a serious problem on many rivers; bridge failure often is attributed to undermining of piers or abutments by scour. A pilot study was made at four bridge sites in Colorado to develop and test guidelines for collecting scour data onsite during high flows. These guidelines potentially could be used to conduct bridge-scour studies or to establish a nationwide bridge-scour data collection program in conjunction with normal high-flow measurements. The methods tested are intended to be compatible with equipment and procedures commonly used in the U.S. Geological Survey streamflow-gaging program. Thirteen scour-prediction equations were evaluated using data collected during this study. Two alternative approaches for future, proposed scour studies are indicated. The type of approach selected would depend on the objectives of the scour study and the flow conditions in the study area. (USGS)