Water-surface profiles near selected bridge sites in Montana

The U.S. Geological Survey (USGS), in cooperation with the Montana Department of Transportation (MDT), collected water-surface profile data at selected highway bridges in Montana. The water-surface profile data characterizes the water-surface elevation and slope upstream and downstream of a bridge. Water-surface profile data were typically obtained for one side of the stream by surveying the left-edge-of-water (LEW) or the right-edge-of-water (REW) along the stream reach. Profile data were obtained mostly during post-runoff conditions, although some data were obtained when bridge scour measurements were made during higher spring runoff conditions. Streamflow associated with the profile measurements was not computed and would require the end user to consult USGS gaging records or use other techniques to estimate the magnitude of streamflow associated with the surveyed water-surface profile data. The water-surface profile data were part of monitoring efforts that included collection of cross-section data at the upstream and downstream sides of the bridge opening and longitudinal streambed profile data. The purpose of the data collection is to determine if scour and channel instability occur in the vicinity of the bridge structures. Data were processed, analyzed, and compiled for bridge scour monitoring, facilitating better understanding, documentation, and prediction of scour processes.