A discussion of Bagnold's (1956) bedload transport theory in relation to recent developments in bedload modelling

✍ Scribed by John S. Bridge

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 262 KB
• Volume: 6
• Category: Article
• ISSN: 0360-1269
• DOI: 10.1002/esp.3290060213

✦ Synopsis

Since Bagnold's (1956) classic paper on the bedload stresses set up during transport of cohesionless grains in fluids, many authors have quoted his work but only recently have his assumptions been examined critically (e.g. Allen (1972); Pratt (1973); Luque and Van Beek (1976); Engelund and Fredsoe (1976); Leeder (1977Leeder ( , 1979a, b), b); Allen and Leeder (1980)). In particular, a recent sediment transport model by Engelund and Fredsoe (1976), which is both simple and apparently accurate, uses many of Bagnold's concepts, and results in a very similar bedload function. This note is intended to show how some of Bagnold's earlier and latest ideas are confirmed and modified by this recent work, and to tentatively suggest further improvement. The following bedload transport theory is taken largely from Engelund and Fredsoe (1976) but with some modifications.

Consider the average drag force, F,, acting on a single sphere moving over a plane bed. For steady average motion of the grain the applied fluid force must be resisted by a frictional force resulting from occasional contacts with the bed and other grains. An expression for this force balance is