SYMBOLS AND DEFINITIONS--Continued 



X ripple length (see Fig. 1) 



X. initial length of ripples newly formed on a flat bed 



A natural or unstrained ripple length 



V kinematic viscosity of water 



p density of water 



p density of sand grains 



T bottom stress 



T T for the initiation of grain motion on a flat bed 



<}> dimensionless measure of the intensity of sand motion, 

 defined by equation (1) 



c 



(j) for the initiation of grain motion on a flat bed 

 (() (j) for the initiation of ripples on a flat bed 

 (fis <))) for the onset of sheet flow 

 Y Stiields parameter, defined by equation (21) 

 to angular frequency, = 2Tr/T 



