Sediment Transport of Gravel in Circular Culverts

Road crossings have an impact on the flood routing of a river or stream, especially if a road crossing has a culvert. While there are methods and procedures for designing the clear water capacity and head loss of a culvert, little is known about the effect of transporting large sizes of sediment through a culvert. Unfortunately, many engineers have experienced either a culvert plugging with large sediment or a culvert with significant reduction in flow capacity from sediment deposits. There is a need to better understand culvert bed load transport of larger sizes of sediment such as gravel and cobbles, the increased head loss from the bed load, and to understand the mechanism for plugging or blockage by large sediment. The following paper presents a methodology and laboratory setup for studying sediment bed load transport in culverts. The results of this paper also present a method for predicting the sediment transport rate of gravel in a circular culvert. The paper is limited to preliminary tests of 6.5-mm (0.256-inch) Dm sized gravel transported as bed load through a 30.20-cm (12-inch) diameter culvert. The authors have tested other sizes of sand and gravel, but those test results will have to be discussed in additional publications