Fixed Instrumentation for Monitoring Scour at Bridges

Research was conducted to develop, test, and evaluate fixed instrumentation that would be both technically and economically feasible for use in measuring maximum scour depth at bridge piers and abutments. A variety of scour-measuring and scour-monitoring methods were tested in the laboratory and in the field, including sounding rods, driven-rod devices, sonic depth finders (fathometers), and buried devices. Two fixed-instrument systems, a low-cost fathometer, and a magnetic slidingcollar device using a driven-rod approach, showed significant promise during initial testing. The project concentrated on installing and testing these two instrument systems under a wide range of bridge substructure geometry, flow, and geomorphic conditions. Both instrument systems met all of the mandatory and many of the desirable criteria established for this research. Cooperative efforts with state highway agencies proved that both systems can be installed with equipment and technical skills normally available to district-level department of transportation maintenance and inspection personnel. The project also provided installation, operation, and fabrication manuals for the low-cost sonic instrument system and magnetic sliding-collar devices.