In 1989, the USGS developed a method for assessing potential channel instability and streambed-scour near bridges (Simon and others, 1989). The “Simon method” called for an inspector to visit each site and record observations of the general geomorphic characteristics on a data collection form. Those data were then evaluated through a standardized index—the Tennessee index—to judge which sites held the greatest potential for future scour concerns. This method was developed by the USGS in Tennessee and was designed specifically for the geographical characteristics of that area.

In numerous USGS bridge-scour investigations that followed, the Simon method of evaluating potential scour was applied and in some cases modified in an attempt to better fit with local conditions of geology, bridge design, and the production of woody debris. Two of the investigations that produced a “modified index” for potential-scour assessment—Doheny (1996) working in Maryland, and Hopkins and Robinson (1997) working in Indiana—are discussed in the papers linked below and could be appropriately applied to Indiana bridges.

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

Hopkins, Mark S. and Robinson, Bret A., 1997, Data base for assessment of streambed scour and channel instability at selected bridges in Indiana, 1991–95; USGS Open-File Report 97-419.