Channel bed mobility and scour on a regulated, gravel-bed river

Book · Sun Dec 31 04:00:00 EST 1995

OSTI ID:220130

McBain, S; Trush, W ^[1]

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1. McBain and Trush, Arcata, CA (United States)

Incipient mobilization of the riffle bed surface is often used as a minimum criteria for flushing flow or maintenance flow prescriptions. Most contemporary bed mobility models require that boundary shear stress be computed. In the absence of detailed vertical velocity profiles, this force is estimated by the depth-slope product. Applying these models to natural rivers is difficult because reaches that minimize form drag and convective acceleration terms in the equation of motion are not the norm. Therefore, we initially approached bed mobility on the Trinity River empirically, using tracer gravels to monitor bed mobility in (1) straight, flume-like reaches, and (2) smaller alluvial deposits within an alternate bar unit (e.g., pool tails, point bars, median bars) during controlled, steady dam releases of 76 m{sup 3}/s and 181 m{sup 3}/s. The 76 m{sup 3}/s release mobilized only the most mobile features (tributary deltas and the heads of median bars), thus was slightly less than incipient conditions for the majority of the river bed surface. In contrast, the 181 m{sup 3}/s release surpassed incipient conditions in most locations. Bed scour followed a similar trend. This paper presents our results and analysis at four long straight reaches. At one of these reaches, the 76 m{sup 3}/s release was very near incipient conditions. The Shields stress ({tau}*D84) was 0.0183. Predictions by four bed mobility models were then compared to our measured {open_quotes}critical{close_quotes} condition; the Parker and Klingeman (1982) model ({tau}*rD84 = 0.0213) and the Andrews (1994) model ({tau}*rD84 = 0.0221) offered the closest predictions.

• OSTI ID: 220130
• Report Number(s): CONF-9507190--
• Country of Publication: United States
• Language: English

Related Subjects

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MATHEMATICAL MODELS
NUMERICAL DATA
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