Fundamentals of Engineering Design
Figure 5.22 Relationship Between Gradient and Bed Forms (after Grant et al., 1990)
Control type describes the nature of the bed controls. Natural examples include bedrock
outcroppings, coarse sediments that form a layer of immobile armoring, or fine sediments that are strongly
cohesive. Weirs or other grade control structures are examples of man-made structures which function as
bed controls.
Bed material is the bed sediment of the river. The bed material description is very important when
determining the flow resistance.
Islands or bars are bed features that have significant effects on flow resistance, channel capacity,
and in-channel sediment storage.
Bar type describes the shape or type of bars present in the reach. Pool/riffle bars are alternating
features that run across the width of the channel and are visible at lower flows. Riffles
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