mining of sand. Equations 55 and 56 describe only the general features of 

 delta growth since the river flow conditions within the delta formation are 

 neglected in the present treatment. The time required for the delta to reach 

 a certain distance y from the original shoreline position is calculated 

 from the following relationship 



y (t) 



D 



4i erfc 



2/Ft 



(60) 



for t > and x = . 



Equation 60 is illustrated in the nondimensional diagram of Figure 27. For a 

 specific wave climate, the above relation implies that an increase in the sand 



2 3 



TIME (et/a J ) 



Figure 27. Maximum delta growth from a sand-discharging river 

 mouth of finite length 



discharge from the river has a proportional effect on the growth of the delta 

 according to the following relation: 



44 



