Simplified method for estimating total streambed scour at bridges in Illinois

A simplified method to estimate total streambed scour was developed for application to approximately 10,000 Local Agency bridges (bridges owned by local governments and not by the State of Illinois). This method consists of using total scour-envelope curves, developed as empirical relations between calculated total scour and bridge characteristics for 303 State Highway Bridges, to estimate the 500-year flood scour. These 303 bridges have been previously evaluated for streambed scour with the application of conventional hydraulic and scour-analyses methods. The bridge characteristics necessary for application of the simplified bridge scour-analyses method are those that can be obtained from an office review of bridge plans, examination of topographic maps and reconnaissance-level site inspection. In comparison with the conventional methods to estimate streambed scour, the simplified method mostly estimates a larger value of 500-year flood total streambed scour.