The transitional portion of the curves of constant wave length are plotted 

 by multiplying the L parameter by 0„5 d/L to get the value d| this point is 

 then located by following the d/L curve to its intersection with the value 

 of the ordinate do 



Plate 9 is Plate 1 from Breakers and Surf and shows generalized curves 

 for the change in velocity,, height, and length of waves in shallow water 

 from deep water to the point of breaking,, These curves refer to waves that 

 approach a shore directly so that there are no effects due to refraction,, 

 The horizontal scale of the graph is d/L , the relative deptho The vertical 

 scale gives the values of the different functions indicated on the various 

 curves „ 



(a) H/H" A theoretical curve for waves of very low steepness showing 



the change in wave height with decreasing depth prior to 

 breakingo It is used to give the height of the wave at any 

 given depth, when the period and height in deep water are 

 known o 



(b) H, /H' An empirical curve showing the ratio between the height of 



the breaker and the wave height in deep water, when the 

 period and depth of breaking are known „ This curve, in con- 

 junction with curve (e), can be used in forecasting wave 

 conditions o 



A theoretical curve for waves of very low steepness showing 

 the change in velocity and length of a wave as it enters 

 shallow water o It is used to give the length and velocity 

 of a wave at any given depth, when the period is known „ 

 This same curve gives the change in direction of a wave as 

 it approaches a straight shore line, and the ratio of the 

 semi-minor and semi-major axis of the particle orbito 



(c) 



sin oc 





sinoc Q 





c/c 





V a s 





l/l 



(d) 



c b/c 



i-iA, 



An empirical curve showing the ratios between the velocity 

 and length at breaking and the velocity and length in deep 

 water, respectively, when the depth of breaking and period 

 are known „ This curve represents a refinement that is 

 usually unnecessary in forecasting wave conditions „ 



(e) 100 H' /L An empirical curve showing the relative depth at which a 

 wave of a given steepness will breako The steepness is 

 expressed in per cent in order to fit the vertical scale „ 

 Breaker This curve, in conjunction with curve (b), can be used in 

 Index forecasting surf conditions „ 



C^ ) H/L A theoretical curve showing the change in wave steepness 

 H' /L as the wave enters shallow water „ 



(g) OoOOlN An empirical curve showing the correction factor for velocity 

 due to steepness „ The curve gives l/LOOO of the value of N 

 in order to make it fit the vertical scale „ It is not used 

 in forecasting but it could be used in the determination of 

 surf characteristics from aerial photographs . 



