Scour has been linked to nearly 95% of all severely damaged and failed highway bridges constructed over waterways in the United States (Leftor, 1993). This is a hazardous condition caused by currents transporting sediments away from bridge piers and similar structures during times of rapid river flow. Scour ablation and deposition can occur during a single high energy flow event, making it difficult to detect deterioration of the structural foundation. This is further complicated by the presence of ice and debris in the waterway.
Current methods for identifying bridge scour primarily rely on “after-the-fact” surveys such as visual inspection by trained divers. Data cannot be obtained in this manner during high flow conditions; however after the event, results may be altered by sediment inflow. Bathymetric radar and sonar monitoring systems are relatively simple and inexpensive devices but have major limitations. Scour depth resolution is coarse, and the devices can yield misleading information if debris or ice are present. Since present methods and devices cannot successfully serve in all environments, state-of-the art systems are crucially in demand.
A patented time domain reflectometry (TDR)-based monitoring system has been developed and field tested by researchers for the U.S. Army Corps of Engineers. This novel system permits civil engineers to conduct continuous real-time, dynamic detection and measurement of scour. It permits automatic resetting to enable measurement of multiple events of erosion and deposition. The high-resolution research model is able to detect changes in river sediment depths of less than 2.5 cm (1 in.).
The TDR Bridge Scour Monitoring System employs a number of inexpensive, vertically oriented sensors that are securely anchored into sediments below the maximum expected depth of scour. The system can easily be installed on new construction or retrofitted to existing structures.
Six Army scour patents are available for licensing and commercialization.