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Gravel Dunes

Summary of research observations at a gravel-bed river

Randal L. Dinehart, 1997,
Gravel Dunes: Summary of research observations at a gravel-bed river

Just as wind-blown sand forms ripples and dunes, a flowing river will create dunes of many sizes from sediment on the streambed. Although most river bedforms are composed of silt and sand, some rivers with gravel or cobble beds can also create dune-shaped bedforms. The amount of force required to move river gravel as bedforms may occur during storm flows or floods.

When gravel dunes form in a riverbed, water flowing over the bedforms changes velocity because of the extra roughness. When gravel dunes migrate, they change the mean bed elevation by scouring sediment or forming gravel bars.

To show how gravel dunes in flooding rivers eventually affect river measurements by hydrographers, this document describes detailed observations of streambed and velocity over the gravel bed of the North Fork Toutle River, Mount St. Helens, Washington.

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06/16/08, Lyn Topinka