Width of Straight Alluvial Channels

The minimum width of an essentially straight stable alluvial channel transporting water with or without a bed material or wash load is related to the tractive strength and the sliding strength of the bank soils, either alluvial or residual. In addition, the variation of the bed level at the banks due to bed forms, alternate bars, and other three‐dimensional flow effects is an important factor. The variation is defined by the ratio of the maximum depth along the bank to the average depth over the bed. The maximum width is not so well defined but depends on the depositional characteristics of the suspended sediment and the development of meandering tendencies in wider channels. Use of bank soil properties to determine stable channel widths indicates that more than one width and slope are possible to carry a given water discharge with or without bed‐material load. For design, the minimum allowable width is usually the best choice.