A Modified Index For Assessment of Potential Scour at Bridges Over Waterways
By Edward J. Doheny
Abstract
A modified potential-scour index has been developed to assess the potential for scour at bridges over waterways. The modified index is based on a potential-scour index used by the U.S. Geological Survey (USGS) Maryland-Delaware-DC District (the Maryland index) and the original prototype potential-scour index developed by the USGS Tennessee District. The modifications were made to (1) improve the technical content of the Maryland index, and (2) provide a more extensive set of index variables for assessment of potential scour at bridges.
This report demonstrates and describes problems that were encountered when using the Maryland index in a study of county-maintained bridges in Maryland from 1993 to 1995. The modifications made to specific index variables and ranking values in the Maryland index are presented and discussed.
A comparison of potential-scour ratings from the Maryland index, as applied to two bridges, is presented. This comparison indicates that the modified potential-scour index yields potential-scour ratings that most consistently reflect scour conditions observed at these bridges.
