|Willis, Joe - ARS (RETIRED)|
Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 18, 1997
Publication Date: N/A
Interpretive Summary: An accurate knowledge of the rate of movement of sand and gravel along the bottom of streams and rivers is important for a number of reasons. It represents material that is subject to erosion and deposition on a stream bed. It is the material that must be dredged from low gradient streams to maintain navigation. It represents a significant fraction of the erosion products from upstream source areas. And, its existence as a blanket on the bed of a channel effectively shields the underlying material from the erosive action of the flowing water. Reliable predictions of the amount of sand and gravel in streams are needed to plan measures for sediment management and control. In this study, the average rates of movement and variation of sand and gravel from Goodwin Creek were measured and compared to standard statistical measures. The results of this research has led to a guide on the number of samples of sand and gravel that are needed to accurately describe their movement in streams. This information is critically needed by people concerned with the management of agricultural watersheds.
Technical Abstract: A large number of samples of sand and gravel transport were measured over a wide range of flows on Goodwin Creek. These samples were collected at two sites and found to vary significantly about the mean value in time. Normalized probability density functions were defined for these sand and gravel transport measurements. The probability density functions were most closely approximated by a gamma form of the probability function. The large coefficient of variation for the transport measurements indicated a large number of observations is necessary to define valid average transport rates over the range of expected flows.