A Method to Select Surface Bed Samples that Represent Bankfull Conditions in Active Gravel Channels

Sediment transport modeling of natural channels should be performed using surface samples that represent the flow conditions of the desired design flow. The most common flow used in natural channel design is the bankfull flow, also know as channel forming flow. However selecting a surface sample that adequately represents this flow condition is a daunting task. This paper presents a method for analyzing surface and subsurface sediment samples to determine the flow condition that occurred when the channel bed surface was created. This method was used in the design of a sand-gravel channel built in Indianapolis, Indiana and was originally discussed in a presentation at the 2004 EWRI World Water Congress in Salt Lake City. This paper documents the method and proposes the conditions when this method may be applied.