Equivalent Roughness of Alluvial Bed

by Leo C. van Rijn, Project Engr.; Delft Hydr. Lab., Delft, The Netherlands,

Serial Information: Journal of the Hydraulics Division, 1982, Vol. 108, Issue 10, Pg. 1215-1218

Document Type: Journal Paper


The eguivalent roughness of a movable bed is considered. Relationships are given which can be used to determine the equivalent bed roughness from the bed material size and the bed-form dimensions. In the case of a plane bed the equivalent roughness is related to the D90 of the bed material. Based on flume and field data, the equivalent roughness may vary from 1-10 D90. Similar values were reported by other research-workers. In the case of bed forms the equivalent roughness is related to the average height and length of the bed forms. Both flume and field data were used to determine a functional relationship. The proposed relationship yields values which are considerably smaller than other existing relationships.

Subject Headings: Bed materials | Hydraulic roughness | Alluvial channels | River and stream beds | Bed forms | Case studies | Flumes | Field tests

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