Maryland Potential Scour Index

An example of bridge piers skewed to approaching flow. During periods of flooding, the right side of these skewed piers may experience sediment scouring. (Click image to enlarge)

During the period 1993 to 1995, the USGS conducted channel-stability assessments at 1,191 bridges over waterways in Maryland. Data were collected at each site to describe physical characteristics of the bridge and stream channel. By making a few modifications to the prototype index developed by Simon and others (1989) in Tennessee, the Maryland Index for potential scour at bridges was established and represented a more refined method for determining potential-scour ratings for bridges in Maryland. Both potential-scour indices—the original Tennessee version and the “modified” Maryland version—assign numerical rankings to specific characteristics of a bridge and stream channel to develop a potential scour rating.

The Maryland index yields a maximum potential-scour rating of 63 and a minimum of 12. A greater ranking value represents lesser scour potential for each index variable. Each of the 13 index variables and their respective rankings are described in Simon and others (1989) and Doheny and others (1996). Both the Tennessee index and the Maryland index provide a means for prioritizing bridges and stream channels for further study.



Doheny, Edward J., 1996, A modified index for assessment of potential scour at bridges over waterways; USGS Open-File Report 96-554.

Simon, A., Outlaw, G.S., and Thomas, Randy, 1989, Evaluation, modeling, and mapping of potential bridge-scour, West Tennessee: National Bridge-Scour Symposium, October 17-19, 1989, Federal Highway Administration, McLean, Va., 18 p.

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