Estimation of Bedform in Alluvial Channels and Streams by Using Regime-Type Velocity Formulas
This paper describes that the regime-type mean velocity formula, Eq.(2),which is similar in form to Lacey’s and Simons’, is not only applicable to flumes with alluvial beds as well as to natural alluvial streams but also it can be an important measure to estimate their bedforms at the same time, the constant K changing depending on their bedforms as seen in Table 1.
Theoretica1 derivation of Eq.(2) is proposed from the we11-known rough turbulent equation proposed by Keu1egan. After discussing the relation between Froude number Fr and relative roughness ks, it is conc1uded that Fr is considered to be almost constant for each bedform. Then, the relation between Fr and K is discussed for various rivers. Eq.(2) has another merit to predict the change of bedforrns as the flow discharge changes. This paper emphasizes that the change of bedforms may happen when the Laursen’s parameter, v*e/w exceeds unity for some existing rivers with fine bed materials.
KeywordsFroude Number Tractive Force Flow Discharge Open Channel Flow Sand Wave
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