Grain sizes in Limerinos's data ranged from very course sand to large cobbles.
Consequently, it follows that this equation is applicable to gravel/cobble bed
streams and to bed regimes similar to those found in such streams and within the
energy spectrum contained in Limerinos' field data. n-values predicted with the
Limerinos equation are sufficiently larger than those predicted by the Strickler
equation indicating that some loss other than grain roughness must have been
present. The Limerinos equation is not applicable to lower regime flow nor does
it forecast the transition between upper and lower regimes.
Burkham and Dawdy (1976) showed that the Limerinos equation could be
used in sand bed streams provided the regime was plane bed. In their analysis
they extended the range of the relative roughness parameter as follows.
R
600 <
< 10,000
Equation 2-17
d84
Figure 2.4. Velocity versus hydraulic radius in a mobile bed stream, used with
permission of California Institute of Technology.
16
Chapter 2
Theoretical Basis for SAM.hyd Calculations
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