Ground-Penetrating Radar: A Tool for Monitoring Bridge Scour

Abstract

The University of Missouri-Rolla (UMR) and the Missouri Department of transportation (MoDOT) acquired ground penetrating radar (GPR) profiles across selected streams and drainage ditches at ten bridge sites in southeast and central Missouri. The objective was to determine if GPR is an effective tool for monitoring bridge scour and estimating the depths and breadths of in-filled scour features. The interpretation of the suite of acquired GPR profiles indicates the toll can be used to accurately estimate water depths in shallow fluvial environments (<20 feet). In certain instances, in-filled (paleo) scour features can also be imaged and mapped. This later information is important because it provides information about maximum scour during peak flow periods. GPR has certain advantages over alternate methods for estimating water depths. GPR can provide an essentially continuous profile-type image of the stream channel and the sub-water bottom sediment along the traverse selected. The GPR antenna are non-invasive and can be moved rapidly across (or above) the surface of a stream at the discretion of the operator. Additionally, the GPR tool does not need to be physically coupled to the water surface and can be operated remotely, ensuring that neither the operator nor equipment need be endangered by flood waters. Perhaps the most significant disadvantage of GPR is that the tool does not work well in clayey sedimentary environments.