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United States Department of Agriculture

Agricultural Research Service

Title: Bed Forms in a Sand-Gravel Stream with Unsteady Flows

Author
item Kuhnle, Roger

Submitted to: American Society of Civil Engineers Water Resources Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 31, 2000
Publication Date: N/A

Interpretive Summary: Knowledge of the rate of movement of water and sediment through agricultural watersheds is important for several reasons. This information is critical for determining the height of flood waters. The rate of movement of the water also directly controls the movement of sediment through the channels and knowledge of its flow patterns can provide information on areas where erosion will be a problem on the watershed. Controlling excessive erosion is critical for managing agricultural lands for sustainable use in an environmentally friendly manner. In this study an acoustic distance measuring device was used to measure time records of the height of the stream bottom during runoff events. This type of information is very rare for streams which contain sand and gravel. This information will be used by researchers to refine and improve current flow and sediment rate prediction methods. This will allow improved prediction of flood heights and the movement of sediment through stream channels. This information will allow more informed decisions to be made regarding land use management in agricultural watersheds.

Technical Abstract: An acoustic distance measuring device was used to automatically collect bed elevation records in the Goodwin Creek Experimental Watershed. The bed material at the study site is composed of a mixture of sand and gravel with a median diameter of 8.3 mm. Bed forms were found for all flows in which a significant portion of the bed sediment was in motion. For the runoff events for which data was collected, bed form periods and spacings were found not to be a function of boundary shear stress. This was attributed to the fact that the coarser grain sizes were not in motion over most of these flows. The height of the bed forms was found to increase while the friction factor was found to decrease with increasing boundary shear stress.

Last Modified: 10/22/2014
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