providing three degrees of freedom for self-adjustment of the channel.
The relationship between these three parameters and discharge – proceed-
ing in a river system in the downstream direction – has been based mainly
on measurements carried out on the Indian subcontinent and is usually
expressed as (Blench, 1969)
B"Q1/2, (8.24a)y"Q1/3, (8.24b)S"Q^ 1/6. (8.24c)Lacey and Pemberton (Ackers, 1983) generalized the basic régime
equation into
VaR(b1)/2Sb (8.25)whereaandbvary with sediment diameter. The power bis 1/4b 1
with the lower limit for d2 mm and the upper for 0.2 mmd0.1 mm.
Lacey’s original equation
V0.635(fR)1/2 (8.26)wheref(2500d)1/2(din m, Vin m s^1 ), combined with equations (8.25) or
(8.24), leads to the basic régime statement
RIVER MORPHOLOGY AND RÉGIME 329
Fig. 8.3 Meandering stream