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  California Water Science Center

Evolution of Coarse-Gravel Bedforms


This sequence of graphs shows bed elevation at a stationary point as measured by sonar at the North Fork Toutle River during storm flow. A steep-fronted dune (trough-to-crest height = 35 cm) passed the sounding point at 22:20 hrs. Average dune heights increased abruptly and the local mean bed elevation increased about 0.5 m by the next day. Dune heights of the largest bedforms were nearly 40 cm.

Most of the large bedforms were superposed with minor, asymmetric bed features, with heights of less than 10 cm. In some instances, the superposed features had well-defined slipfaces with heights nearly 20 cm. Wavelengths of the large bedforms, measured trough-to-trough, were 10 to 20 m.

bed elevation showing coarse-gravel bedforms

Bed elevation from sonar showing evolution of coarse-gravel bedforms (13 Kb)

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