A 4.6-m wide by 5.5-m long scour basin was built in the hydraulics laboratory of the University of Nebraska in Lincoln to test the effectiveness of several energy dissipation structures for reducing scour downstream of box culverts. A 3.5-m long, 0.5-m wide box culvert was installed upstream of the scour basin as a test bed for the energy-dissipation devices. Flow rate and inlet velocity in the box culvert is controlled, and the tailwater in the scour basin can be adjusted. A Seatek ranging system was mounted on a beam above the basin to measure the depth and geometry of the scour-hole as it develops. The system has an array of 16 depth measuring acoustic sensors. A low velocity winch pulls the array over the length of the scour basin on a rail system, and the resulting matrix of depth measurements can be used to assess the time history of the geometry of the scour-hole. Discharge and depths at the outlet of the box culvert are also measured for each test. Time varying geometric changes of the scour-holes that develop for a range of flow conditions are reported, including: 1. Flows in which a drop structure is installed in the box culvert. 2. Flows in which a sill is installed downstream of a drop structure in the box culvert to reduce outlet energy. The energy dissipation methods listed above are being investigated by the Nebraska Department of Roads as alternatives for reducing the cost of box culvert installations.
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